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Layout SmartRoute User's Guide

1. ii N Met Nama er 12v A 33 TT s I Hap j g Routing Weight Routing weight biases the order in which nets are routed A value of 100 assigns the highest priority for routing the net will be routed sooner and a value of one the lowest priority the net will be routed later This allows you to route critical nets first For example you can assign a net with critical clock speeds or a net that is subject to interference a higher priority to assure shorter connection lengths Routing Weight allows you to select the order of routing SmartRoute first selects all nets with a weight of 81 100 that have unrouted segments then attempts to route them starting with the highest weight and the widest width It then selects all nets with a weight of 61 100 including routed nets and attempts to route them starting with the highest weight and the widest width During this pass it also attempts to remove conflicts from the routed nets Then SmartRoute continues in the same manner with nets with a weight of 0 60 If you don t select a Routing Weight the priority of routing is determined by the neural network The Routing Weight values in SmartRoute reflect the values for weight set in Layout Plus You can change these values in SmartRoute Keep in mind that slight increments in the routing priority value have the same effect as dramatic increments For example if all nets are given a routing priority
2. Display dot grid AutoPan Square vias Arcs in connections High contrast mode For general use 32 MB of RAM is the recommended minimum amount of RAM For routing larger boards four layers 2 000 connections more memory 1s recommended For boards with six or more routing layers and over 2 500 connections a minimum of 64 MB of RAM is recommended SmartRoute uses about 10 to 15 more memory than other shape based autorouters This additional memory is used to create the multi sided neural shapes that in turn permit the diagonal and angled routing that contributes to SmartRoute s high quality routing If there is not enough memory in your system the autorouter will not route In the event the autorouter will not route check the SRTLOG TXT file in the Layout Plus directory for the message Not Enough Memory If you receive this message it may be possible to free up enough memory from other applications Although SmartRoute uses virtual memory it will not run unless there is enough available physical memory To determine the amount of memory available on your system exit Windows and at the DOS prompt type MEM On the line labeled Total Memory examine the values for Total Used and Available If you have 32 MB on your PC and if the value for Total is 32 MB but the value for Free is significantly less 5 to 6 MB you can retrieve and use some of this memory To do so determine where the additional memory is u
3. SRBACK RBK 20 Find Goto command 7 H Help menu 2 Highlight Net command 7 Hints Checkbox command 13 Hints dialog box 13 hints new user 13 horizontal routing 28 hot spots 16 I K Identify Net command 7 Identify Pin command 7 information routing 3 interactive routing 45 49 59 Index L layers routing direction by 28 Layout Plus compatibility with 9 length of nets 26 location on board finding 17 locking nets 26 low resources 56 magnify board 4 Manual Route command 50 manual routing 50 manufacturing passes Evenly Space Tracks 55 Track Corners 35 MAX files closing 21 opening 9 saving 20 memory requirements 9 55 56 Memory routing pass 33 menus Auto 12 Edit 71 File 11 Help 12 Options 12 pop up 12 Tool 11 View 11 minimize net length 26 minimum width 26 mitered corners 35 modifying segments 49 multilayer boards routing 42 44 N Net Properties command 24 nets order for routing 25 priority for routing 25 properties 21 26 routing 46 width 26 network neural neural costs 3 network shapes 3 new user hints 13 O obstacles 54 Open command 79 Open Design File dialog box 19 opening designs 19 Options menu 2 order routing 25 orthogonal corners 35 routing 43 P Q pads outside board outline 54 primary 30 width 30 parameters 23 27 guidelines 57 layers 26 Parameters command 27
4. 52 5 e atit dm ER edo P E ER RERO 50 Deleting TOULES iHe eni e e petit 51 Design checklist and common errors 53 Solving routing problems eeeeeeeeeeeee 55 Suggested reference material 63 ON 65 iv OrCAD Layout SmartRoute User s Guide About this manual The OrCAD Layout SmartRoute User s Guide is intended to familiarize you with SmartRoute s autorouter and interactive routing capabilities To help you learn SmartRoute effectively this manual covers the tasks you will perform beginning with the most basic tasks and then progressing to more advanced tasks The appendices at the end of the manual address routing strategies and troubleshooting techniques Before you begin This manual assumes that you are familiar with Windows that you have some knowledge of printed circuit board design and that you are familiar with OrCAD Layout Plus To learn about Layout Plus read the OrCAD Layout User s Guide and read the numerous Layout online help topics Symbols and conventions OrCAD printed documentation uses a few special symbols and conventions The keyboard The keys on your keyboard may not be labeled exactly as they are in this manual All key names are shown using small capital letters For example the Control key is shown as CTRL the Escape key is shown as ESC Keys are frequently used in combinations or seque
5. About SmartRoute Although difficult to measure you will recognize quality routing when you see it The elements that define quality routing are as follows A preference for 45 diagonal routing over X and Y orthogonal segments The ability to assign directions other than X or Y to different layers The collection of connections that bridge two areas or parts on the board into a bundle of tracks all using a similar track pattern A minimization of vias A minimization of wandering tracks a Other features such as circuit flow Predicting routing time and percent of completion In SmartRoute you can use the Analyze Parameters tool to predict routing time and routing completion The prediction is an estimate which can be fairly close or wildly inaccurate depending on the complexity of the design The more average the board is the more accurate the prediction The prediction is most useful as a measure of the effect of changing placements spacing rules and so on SmartRoute s neural network is familiar with the standard boards used today two four six eight ten and sixteen layer boards through hole SMD top SMD bottom fine pitch SMD and PGA Additionally the parameters pad size spacing via size and so on are based on the practices of skilled designers The neural network will not recognize boards in excess of 16 layers 20 x 20 or with unconventional design parameters such as a 75 mils via or
6. Area command is extremely useful for routing dense areas on the board Routing dense areas using this command is fast and effective You may find that all the connections within the area can be routed without contentions By routing the densest areas in this manner you can increase your chances of routing 100 of the board Routing components in dense areas using the AutoRoute Component command achieves similar results In addition to using these commands use the strategies described in Component placement strategies in this appendix Component placement strategies The following guide will assist you in placing individual parts Routing channel While placing the parts in Layout Plus place parts on the routing channel grid setting that SmartRoute will use Calculate this value by adding the track size and the clearance values in Layout Plus The following are suggested channels Track clearance mils Suggested routing grid mils 12 13 25 12 12 10 10 20 8 8 16 2 3 6 6 12 5 Track clearance and suggested routing grids Do not block routing channels Place parts so that their pads align with the pads of other parts in both the X and Y direction OrCAD Layout SmartRoute User s Guide 59 Appendix B Solving routing problems SMD spacing SMD pads on different parts must be separated sufficiently to allow for fanout The separation must consider the fanout via diameter track length size of the part number of pins h
7. IC pad You can route these boards using SmartRoute but the Analyze Parameters tool will not yield accurate results Note In order for the Analyze Parameters tool to provide a more accurate prediction of routing time you must calibrate SmartRoute For information on calibrating SmartRoute see Calibrating SmartRoute in Chapter 2 Getting started 6 OrCAD Layout SmartRoute User s Guide Chapter 2 Getting started This chapter describes how to start SmartRoute It also lists compatibility issues that exist between Layout Plus and SmartRoute and describes SmartRoute s memory reguirements Calibrating SmartRoute After installation but before using SmartRoute OrCAD recommends that you run the calibration program Calibration loads a board into SmartRoute and routes it From the length of time it takes to route this board on your system SmartRoute can assess your system s impact on routing speed Calibration significantly affects the accuracy of the Analyze Parameters tool which you can use to predict the routing time and percentage of completion for a board Seealso For more information on the Analyze Parameters tool see Analyzing routing parameters in Chapter 5 Setting up the board for routing To calibrate SmartRoute 1 From the Windows Start menu choose Programs 2 Choose the OrCAD Design Desktop program group and then choose SmartRoute Calibrate SmartRoute opens and loads the calibration board and routes it Or
8. Parameters dialog box 27 28 passes manufacturing Evenly Space Tracks 35 Track Corners 35 routing 3 23 31 33 Fan Out Used SMD Pins 31 33 Memory 33 Pattern 33 Push N Shove 34 Ripup 34 Pattern routing pass 33 Pause AutoRouter command 37 pins finding 7 placing components strategies 58 61 planes dividing 54 layers 26 nets 26 pop up menus 2 power for routing 5 OrCAD Layout SmartRoute User s Guide 67 Index predicting routing time 31 58 preparing designs for routing 53 Pre Route Synopsis command 37 38 primary pad 30 Primary Pad parameter 30 Primary Track parameter 30 priority routing 25 problems design preparation checklist 53 routing 55 56 properties Length Minimize 24 26 net 23 21 26 Route Action 24 26 Routing Weight 24 25 Track Width 24 26 Push N Shove routing pass 34 R RAM requirements 55 reading suggested 63 Redo 45 reference material 63 requirements memory 9 Restart AutoRouter command 37 restricted areas 54 Ripup routing pass 34 Route Action Fanout Plane 26 Fanout Route 26 Locked 26 No Route 26 Route 26 route keepouts 54 routing a selected area 46 59 algorithms 3 31 33 autorouting 37 39 batch autorouting 40 channels 30 59 completion percentage 56 57 components 46 connections 47 contention 5 deleting tracks 48 51 direction by layer 4 28 43 44 interactive 45 49 59 68 OrCAD Layout SmartRoute Use
9. Passes 32 Save As 20 SketchA Track 46 49 Stop AutoRouter 37 Undo 45 Unroute Board 51 Unroute Conflicts 57 Unroute Connection 57 Unroute Net 5 OrCAD Layout SmartRoute User s Guide 65 Index Unroute Segment 51 Zoom All Fit 14 Zoom Center 4 Zoom In 4 Zoom Out 14 completion percentage 56 57 component placement analysis 58 59 components finding 7 pads outside board outline 54 placing 58 61 routing all connections of 46 spacing 60 connection hot spots 16 connections arcs in 9 routing single 47 contention 34 57 routing 5 copper areas 54 costs in autorouters 3 neural cost 3 via costs 3 D data routing 13 deleting tracks 48 31 density 58 59 Density Graph command 16 58 design preparation checklist 53 design rule check 45 56 designs backup 20 closing 21 opening 9 parameters 25 preparation checklist 53 saving 20 units 29 dialog boxes Backup Interval 20 Batch Design File 40 Hints 13 Open Design File 19 Parameters 27 28 Routing Passes 32 33 66 OrCAD Layout SmartRoute User s Guide Save As 20 Save Routed Design File As 40 Start Batch 40 direction by layer 43 44 dividing plane layers 54 drawing circuitous paths 49 E edge finger connections 54 Edit menu Exit command 21 exiting SmartRoute 27 F G Fan Out Used SMD Pins routing pass 31 33 fanout 37 33 plane 26 route 26 File menu 7 7 files MAX 20
10. analyze routing problems and correct them The autorouter has stopped the time counter has stopped or the autorouter is not advancing The most likely cause is an inadequate amount of physical RAM in your CPU SmartRoute s autorouter uses a variety of shapes triangles rectangles pentagons and others These multi cornered shapes require more memory for constructing a routing map than the conventional shapes used by other shape based routers The benefits of using these shapes are diagonal segments and quality routing the cost is 10 1596 more RAM The following is an approximate guide to RAM requirements for SmartRoute Board characteristics Available memory requirements Two to four routing layers up to 1000 16 MB connections Six routing layers up to 1500 32 MB connections Six to eight routing layers up to 3500 48 MB connections SmartRoute memory requirements OrCAD Layout SmartRoute User s Guide 55 Appendix B Solving routing problems The autorouter is too slow OrCAD recommends that you run SmartRoute on a Pentium class computer Router achieves low percentage i e 75 85 completion There could be many reasons Check the following If routing a previously routed multilayer board with power planes check to ensure that the copper used to construct the power planes in the original board design has been deleted If the power plane is still covered with copper SmartRoute cannot penetrate the copper
11. by neural cost and consider the connectivity of the board In all cases these algorithms although traditional in the printed circuit board industry have been modified to meet the requirements of neural routing OrCAD Layout SmartRoute User s Guide 3 Chapter 1 About SmartRoute Angled direction by layer In SmartRoute you can direct the autorouter to route in non orthogonal directions on each layer of a multilayer board The autorouter assigns a connection to a layer based on the user assigned layer direction and the connection s slope or tangent SmartRoute then routes the track along the slant or approximate hypotenuse of a triangle as opposed to routing orthogonally along the X and Y legs of the hypotenuse When routing using a direction by layer The approximate hypotenuse track length is shorter than the X and Y length The board will have fewer vias Shorter track length provides more flexibility when placing parts Combined with fewer numbers of vias per connection these considerations greatly accelerate the routing process Additionally there is an increased probability of routing to 100 completion The choice of which direction to use on each layer is entirely yours although SmartRoute initially assigns directions when it loads a board In fact the directions may be limited to the conventional horizontal and vertical directions if desired During the autorouting sequence the autorouter selects the connections tha
12. diagonal routing primary direction by layer minimum via count minimized wandering and bus structure These characteristics were used to establish neural costs The SmartRoute neural network determined the relationships between the physical characteristics of these boards and the board being autorouted Appendix C includes a listing of suggested reading material for further information on neural networks 2 OrCAD Layout SmartRoute User s Guide Chapter 1 About SmartRoute Neural costs Neural shapes All autorouters use a feature called cost for their routing algorithms Cost determines how difficult it is for the autorouter to perform a given activity Using vias as an example on a scale of 1 100 a via cost of 1 makes it easy to install vias and in the absence of other costs results in a board with many vias A via cost of 100 on the other hand prevents the placement of vias even in areas of the board where vias are desirable Neural costs are not static instead they change dynamically throughout the routing process The neural costs are adapted in terms of routing completion They are adjusted as the board s density changes due to routing The dynamic adaptation of cost applies for all cost driven parameters A significant neural cost is connection sequencing which controls the order in which connections are selected for routing Many autorouters use connection length as the primary selection variable SmartRoute on the ot
13. for routing For information on using the new user hints feature see New user hints in this chapter Auto menu The Auto menu includes commands for running the pre route synopsis and autorouting It also includes commands for interactive and manual routing LL See For information on autorouting and batch routing see Chapter 6 Autorouting and batch routing For information on interactive and manual routing see Chapter 7 Editing the board Help menu The Help menu provides access to the SmartRoute online help The SmartRoute online help provides a description of every command and dialog box in SmartRoute and includes key processes and reference information The Help menu also includes the About SmartRoute command which displays the version number licensing and copyright information for SmartRoute Pop up menus The SmartRoute pop up menus provide easy access to frequently used commands You can display pop up menus by pressing the right mouse button The pop up menus provide commands that are appropriate for the current activity For example during autorouting the pop up menu displays the commands Pause and Stop However if the autorouter has been paused the pop up menu displays the commands Restart and Stop Z Tip During autorouting SmartRoute displays an hourglass Even when this hourglass is displayed you can still access menu commands and pop up menu commands although some commands will be dimmed and unavailable fo
14. for the current batch run delete the existing SROUTE LOG before you start the batch routing To perform batch routing 1 From the Options menu choose Batch Setup The Batch Design File dialog box displays 2 Locate and select the file that you want to add to the batch queue and choose the OK button The Save Routed Design File As dialog box displays 3 Inthe File Name text box enter a name and select the target directory for the post route file then choose the OK button 4 Repeat steps 1 through 3 for each file that you want to add to the queue 5 When you are ready to start the batch operation choose AutoRoute Batch from the Auto menu The Start Batch dialog box displays It lists all the files in the queue for batch routing Any files listed will be routed during batch routing Bateh F ikani Fiala Filerrarros S0 R CAI LAYOUT oA PL LS DER OSRHORARDT MAX CIRCA PATARA APUTA PLEITE NERIMA MAX COAG Dlane liririr One Drie b 6 Select and delete any files that you do not want to include in the batch operation 7 Choose the OK button to start batch routing SmartRoute routes each design in sequence SmartRoute displays SROUTE LOG 40 OrCAD Layout SmartRoute User s Guide Chapter 6 Autorouting and batch routing Setting up and routing two layer boards LI LQ On a two layer board signal power and ground connections are routed on two routing layers without using planes When routing a two layer b
15. intelligence that will result in the best routing OrCAD Layout SmartRoute User s Guide 1 Chapter 1 About SmartRoute While the concept of a neural network is relatively new to EDA it is widely used elsewhere One of the better known uses is in the financial marketplace where it is used in analyzing and predicting stock market trends Virtually every financial institution involved in stock and currency trading uses neural networks as an investment tool Other areas where neural networks are used extensively are in character recognition and speech recognition In order for a neural network to produce a solution it must have input data consisting of multiple sets of data similar to data describing the solution The neural network studies this historical data a feature called neural network training In the case of financial analysis and prediction where the solution is a prediction of stock price currency index value and so on the input data is a time series of both the financial item that is to be predicted as well as a time series of related variables that may have a relationship to the stock of interest For example to predict the closing stock price of an electronic company tomorrow you need 200 300 days of previous historical closing data on the stock as well as 200 300 previous closing days of other variables that you think might have a bearing on predicting the stock s closing value These variables might be the Index
16. is routed between two pads it may be placed on a 20 mils channel near one or the other of the IC pads Running the Evenly Space Tracks manufacturing pass shifts this track to the center of the space between the IC pads Track Corners Use this feature to choose either orthogonal or mitered corners OrCAD Layout SmartRoute User s Guide 35 Chapter 6 Autorouting and batch routing Autorouting LI This chapter discusses the autorouting and batch routing processes It describes how to run a pre route synopsis how to start stop pause and restart the autorouter and hov to run batch routing It also guides you through the routing of a two layer and a four layer board See For information on setting up the board for routing see Chapter 5 Setting up the board for routing It is essential that you set up the board properly to ensure routing success After checking the net properties and parameters selecting routing passes and running the pre route synopsis you can perform autorouting The autorouting process consists of the sequential resolution of the routing passes that you select in the Routing Passes dialog box When SmartRoute is satisfied that it has completed all possible connections using that pass it moves on to the next specified routing pass You can suspend routing temporarily using the Pause AutoRouter command on the Auto menu To restart the routing from where it left off choose the Restart AutoRouter command f
17. layer Disabled No routing occurs on the layer Fanout The router will fanout vias on this layer but will not otherwise route on it Use this option when you wish to fanout the layer containing the SMD pads and also restrict routing on that layer Plane The layer is reserved for use as a plane layer upon its return to Layout Plus When this option is selected the layer is no longer displayed in the Parameters dialog box Vertical The tracks are biased to be routed vertically Horizontal The tracks are biased to be routed horizontally Any Direction The router is not biased in any direction The suggested use for this option is on the third layer of a three layer board Do not use this option on more than one layer 28 OrCAD Layout SmartRoute User s Guide Chapter 5 Setting up the board for routing Angled options Options include right and left 45 angles 1 o clock 2 o clock 4 o clock and 5 o clock angles These options will bias the layer in the direction selected The options may be used for all layers on a multilayer board although top and bottom layers are usually horizontally or vertically biased These options are usually used by board designers to achieve shorter track lengths and fewer vias These options can only be used on multilayer boards Summary While itis Example In this example you are routing the top and bottom layers and j Pun demi pen t reserving layers 2 and 3 for planes This means that during routing trac
18. manual routing or fixed in Layout Plus The number of contentions displays in the status bar During routing the number of yellow circles contentions on the board may differ from the number shown in the status bar This is due to the fact that the screen is updated instantly as a connection is routed whereas the data line is updated only after a major routing pass Z Tip If there are still unrouted nets or contentions after routing they may be completed by another combination of push n shove and ripup passes 34 OrCAD Layout SmartRoute User s Guide Chapter 5 Setting up the board for routing Manufacturing passes The manufacturing passes are described below Note As routing occurs via minimization and segment count minimization are performed by the router automatically As a result a separate via minimization pass does not exist To specify manufacturing passes 1 From the Options menu choose Routing Passes The Routing Passes dialog box displays 2 If you have already routed the board deselect all of the routing passes and select the manufacturing passes that you wish to run Or If you want to run the manufacturing passes during routing select the desired passes listed in the dialog box and choose the OK button 3 From the Auto menu choose Autoroute Board SmartRoute runs the selected passes Evenly Space Tracks This pass is used to evenly space tracks between other tracks or pads When only one track
19. more information Using backup Three backup commands make up the SmartRoute backup feature Backup Restore Backup and Backup Interval The Backup command automatically saves the design and generates a file called SRBACK RBK at the intervals you establish Subsequent backups overwrite the previous SRBACK RBK The advantage of backup is that in the event of power outages hardware failure or for whatever reason you can go back to an earlier sequence in the autorouting process To open the last saved version of the design use the Restore Backup command To set the backup interval 1 From the Options menu choose Backup Interval The Auto Backup Interval dialog box displays 2 Inthe Make new backup every n minutes text box enter the interval at which you want SmartRoute to save the design and create the backup file SRBACK RBK If you enter 0 zero in this text box you disable the backup feature 3 Choose the OK button amp Tip OrCAD recommends setting backup intervals of 10 minutes h3 Note Backup intervals reflect real time 20 OrCAD Layout SmartRoute User s Guide Chapter 4 Opening and saving designs To make a backup b From the File menu choose Backup SmartRoute saves the file and replaces the current version of the backup file SRBACK RBK To open the last saved SRBACK RBK file b From the File menu choose Restore Backup SmartRoute opens the current backup file SRBACK RBK Z Tip Ifyou restor
20. of 50 and you change the routing priority of one net to 51 the net set at 51 will be routed first There is no need to set that net s routing priority to 90 OrCAD Layout SmartRoute User s Guide 25 Chapter 5 Setting up the board for routing Length Minimize SmartRoute minimizes the lengths of the unrouted connections on the board immediately before autorouting in accordance with the Length Minimize setting for each net The setting options are described below None No minimization occurs Min Dist minimum distance The connections are rearranged to result in a minimum total length Daisy The net retains the from to sequence in the board design Horizontal The connections in a net are rearranged to be horizontally biased This setting is primarily used for power and ground nets Vertical The connections in a net are rearranged to be vertically biased This setting is primarily used for power and ground nets Route Action The route action property provides the router with instructions for routing a net Default If a net is connected to SMD pads and if there are no more than two routing layers on the board the net is routed without being fanned out from the SMD pad on a board with more than two routing layers the net is fanned out then routed Default is the normal mode for the autorouter and should not be changed unless for a specific purpose Route The system routes the net without a fanout No Route The n
21. while using SketchATrack b After selecting the connection type the number that corresponds to the desired layer 48 OrCAD Layout SmartRoute User s Guide Chapter 7 Editing the board To create vias while using SketchATrack 1 2 3 Sketch the track to the desired via location Release the left mouse button Type the number that corresponds to the target layer SmartRoute changes layers the appropriate color for the target layer displays Complete the track on the target layer To modify segments using SketchATrack 1 Select the point at which you want to begin to modify the segment with the left mouse button The connection and its pins are highlighted Press the left mouse button and drag the mouse to create the new path Release the left mouse button at the point at which you want to stop modifying the segment The autorouter erases the segment of the routed track and attempts to reroute it along the new modified track To draw circuitous paths using SketchATrack b Sketch the desired roundabout path in short straight increments releasing the mouse button as you complete each segment SmartRoute autoroutes the path to each point in turn eventually creating the desired track OrCAD Layout SmartRoute User s Guide 49 Chapter 7 Editing the board Manual routing You can use the commands on the Tools menu to manually route areas of the board and for general board editing The Manual Route command offe
22. with a vertical bias then choose the OK button Seealso For more information on setting parameters and on using the Analyze Parameters option see Chapter 5 Setting up the board for routing 5 From the Auto menu choose Pre Route Synopsis and examine the report Seealso For more information on running the pre route synopsis see Pre route synopsis in this chapter 6 Close the report then choose AutoRoute Board from the Auto menu The power and ground tracks are routed along with the signal connections on the two layers OrCAD Layout SmartRoute User s Guide 41 Chapter 6 Autorouting and batch routing In the LAYOUT SAMPLES DEMOSR directory there is a two layer board set up for this function BOARD2 MAX It may be helpful to experiment with this board Set the parameters for BOARD2 MAX as follows Via Width 0 055 Primary Pad 0 06 Primary Track 012 Clearance 0 013 Top layer Horizontal Bottom layer Vertical Setting up and routing multilayer boards The objectives of this section are to demonstrate multilayer more than two layers routing and the concept of direction by layer The step by step instructions tell you how to set up and route an eight layer SMD board with four routing layers and four planes The components are all SMD parts and are located on both the top and bottom layers of the board For this exercise use BOARD3 MAX in the LAYOUT SAMPLES DEMOSR directory Once yo
23. you make a trial run with only the Fan Out Used SMD Pins option selected in the Routing Passes dialog box before you commit the board to the total autorouting sequence If you find that the router cannot implement fanout for a significant number of the total number of pins about 1096 scheduled for fanout it is highly likely that 10096 completion will not be achieved In this case you should adjust the placement of the components in the areas of the board where the fanout failures occurred Pattern The pattern routing pass uses a collection of different strategies each addressing a particular type of pattern The router searches the board for such patterns and routes them using the appropriate pattern strategy OrCAD recommends that you always use this pass OrCAD Layout SmartRoute User s Guide 33 Chapter 5 Setting up the board for routing Contention Push N Shove The push n shove routing pass is the most powerful routing pass in SmartRoute It pushes and shoves existing tracks out of the way in order to make room for new tracks It routes on a diagonal It has no limits on how far it can push other tracks and can jump over vias and pads Ripup Upon completion of the push n shove routing pass there may be spacing violations or contentions on the board contentions appear as small yellow circles Generally subsequent passes of the various routing passes remove the contentions In very dense boards however contentions ma
24. your design in Layout Plus Unconnected pads outside the board outline are acceptable A design must have a complete closed board outline A design without a board outline or with a partial outline is not valid When creating the board outline always use the Board Outline obstacle type in Layout Plus and place it on the global layer There cannot be more than one board outline in the design Obstacles on routing layers are potential problems When creating obstacles on routing layers in Layout Plus ensure they do not short out pads in different nets Leave enough room between obstacles and connected pads to avoid spacing violations during routing When placing components leave enough clearance between connected pads and the board outline to avoid spacing violations during routing Edge finger connections are a frequent offender in this category If you add mounting holes to a layered board SmartRoute will ignore the drill on the inner layers Consequently in Layout Plus you must define a pad in the Padstacks spreadsheet for the internal layers The presence of even a 1 mil pad will cause SmartRoute to observe the drill size for the mounting hole 54 OrCAD Layout SmartRoute User s Guide Appendix B Solving routing problems With the right set of parameters and enough physical space to route the connections SmartRoute will achieve 10096 completion There are times however when this does not happen Use this appendix to
25. CAD Layout SmartRoute User s Guide 7 Chapter 2 Getting started Starting SmartRoute Start SmartRoute from the Layout Plus session frame Caution Starting SmartRoute by double clicking on SROUTE EXE opens SmartRoute in demonstration mode and you cannot save your design To start SmartRoute o From the Tools menu in the Layout Plus session frame choose SmartRoute h3 Note Ifyou are running a version of Layout other than Layout Plus the Tools menu lists SmartRoute Demo instead of SmartRoute In this case you will only be able to run SmartRoute in demonstration mode The SmartRoute session frame Once you start SmartRoute you see the SmartRoute session frame This is the area where the board is displayed p IPTE dane Hin lacked The SmartRoute session frame Before you load a design the title bar at the top of the session frame reads No design file loaded When you open a design that is replaced with the design s name In SmartRoute you can only open one design file at a time At the bottom of the session frame you see the names of the seven routing passes available for the autorouting sequence See For information on routing passes see Specifying routing passes in Chapter 5 Setting up the board for routing 8 OrCAD Layout SmartRoute User s Guide Chapter 2 Getting started Compatibility with Layout Plus Memory The following Layout Plus features are not yet supported in SmartRoute
26. OrCAD Layout SmartRoute User s Guide Copyright 1998 OrCAD Inc All rights reserved OrCAD OrCAD Capture OrCAD Layout and OrCAD PSpice are registered trademarks of OrCAD Inc Enterprise CIS Enterprise Component Information System OrCAD Capture CIS OrCAD Express OrCAD Express CIS OrCAD Layout Engineer s Edition OrCAD Optimizer and SmartRoute are trademarks of OrCAD Inc Microsoft Visual Basic Windows Windows NT and other names of Microsoft products referenced herein are trademarks or registered trademarks of Microsoft Corporation All other brand and product names mentioned herein are used for identification purposes only and are trademarks or registered trademarks of their respective holders MN 01 5049 Fourth Edition 1 July 98 Technical support 503 671 9400 Corporate offices 503 671 9500 OrCAD Japan K K 81 45 621 1911 OrCAD UK Ltd 44 1256 38 1 400 Fax 503 671 9501 General email info orcad com Technical support email techsupport orcad com Web site www orcad com OrCAD Design Network ODN www orcad com odn 9300 S W Nimbus Ave Beaverton OR 97008 USA Contents Abo tthisman al i V Before you begin niece dise dti hide ce tete eterne redet dete e deeds v Symbols and conventions meti iEn rokou v The keybo td one Ra HER aet V TeXt ther REIR eremi Ret bep vi Chapter 1 About Smarthoule 4 erento itin kunda da pan cac s dna a 1 Neural networks
27. When you route pin to pin the autorouter attempts to take the midpoint between the IC pad rows and the most direct path For multi connection nets it is possible to route from a pin to a track rather than from a pin to a pin The layer that is automatically selected by the SketchATrack command is determined by the direction you sketch from the start pin The shorter the track the more successfully the autorouter will match the line you draw Long curvy lines are not followed as closely The length of a routed connection displays in the status bar during routing For example the entry U13 12 to U6 6 4 325 1348 indicates that the connection between the listed pins of net 1348 is 4 325 inches in length To route a track using the SketchATrack command 1 From the Tools menu choose SketchATrack 2 Select the connection that you want to sketch The connection its first and last pins and the complete net are highlighted Press the left mouse button and drag the mouse to draw the desired path Release the left mouse button The autorouter routes the connection to the point where you release the button 5 Press and drag again to continue drawing the connection to the end pin When you ve sketched a track close enough to the end pin SmartRoute completes the connection To delete a sketched track b To erase part of a sketch loop the sketched track back over itself at the point where the deletion is to occur To change layers
28. ack and click the left mouse button To stop manual routing choose Exit from the pop up menu 50 OrCAD Layout SmartRoute User s Guide Chapter 7 Editing the board Deleting routes LI In SmartRoute it is possible to unroute routed tracks using five commands on the Auto menu You have several levels of routing deletion to choose from Unroute Board Use the Unroute Board command to delete all routing on the entire board even tracks that were routed in Layout Plus including locked preroutes or in previous SmartRoute sessions When you choose this command SmartRoute prompts you to make sure that you really want to unroute all of the nets on the board This command cannot be undone using the Undo command Unroute Net Use the Unroute Net command to unroute one routed net To do so choose the Unroute Net command from the Auto menu and select the net that you want to unroute Unroute Connection Use the Unroute Connection command to unroute one connection a connection is an unrouted net that connects two pads To do so choose the Unroute Connection command from the Auto menu and select the connection that you want to unroute Unroute Segment Use the Unroute Segment command to unroute one segment of a connection or net a segment is the track between two vertices To do so choose the Unroute Segment command from the Auto menu and select the segment that you want to unroute Unroute Conflicts Use the Unroute Conflicts command t
29. ads on the top layer superimpose themselves over the pads on the bottom layer If possible similarly sized parts should be reflected on the top and bottom layers In other words a 100 pin SMD part on the bottom layer should be aligned with a 100 pin part on the top layer When you must place a 100 pin four sided part on the bottom layer under a 200 pin four sided part on the top layer line up one corner and the two associated sides Furthermore two pin discrete parts on the bottom layer should be located directly under SMD IC parts on the top layer 60 OrCAD Layout SmartRoute User s Guide Appendix B Solving routing problems To evaluate a suspect layer for fanout problems open the Routing Passes dialog box turn off all routing passes except for Fan Out Used SMD Pins then choose the OK button Next use the AutoRoute Area command to autoroute the area of concern Examine the results for fanout failure indicated by small yellow circles If there is in excess of 5 896 fanout failures as compared to the total number of fanouts after all five fanout passes adjust component placement in this area More tips and tricks Before loading designs created with Layout Plus versions earlier than v7 10 for routing in SmartRoute open them in Layout Plus and save them with a new name This will give you a backup copy of the design Loading and saving designs also updates the design so that SmartRoute can work with it more efficiently Fa
30. ant to clear your computer s memory prior to autorouting 56 OrCAD Layout SmartRoute User s Guide Appendix B Solving routing problems The router seems slow when routing angled layers This is true Routing a multilayer board using horizontal and vertical routing is faster than routing with a combination of horizontal vertical and angled tracks It is more difficult and time consuming to push and shove a segment on an angle than it is to push and shove a segment either horizontally or vertically An approximate guide for estimating the additional time is to add approximately 15 per angled layer over the time estimated for horizontal and vertical routing For example if routing a four layer board using horizontal and vertical routing took one hour then routing horizontal 45 up 45 down vertical would take about 1 hour 20 minutes Only a few connections or contentions are left unrouted Generally you will find that upon completion of routing the results fall into one of three categories 10046 routed 10 20 unrouted Clearly a major problem exists in this situation There is probably a mismatch among the area of the board the number of routing layers and the number of connections to be routed 1 2 or less of the connections left unrouted In this situation follow the procedures below to achieve 100 routing When followed these procedures may prove to be successful in routing those final few connections Param
31. are selected and select the Mitered option for the Track Corners manufacturing pass Choose the OK button 5 From the Auto menu choose Pre Route Synopsis Review the report to ensure that the database parameters are as you would expect then close the report 6 From the Auto menu choose AutoRoute Board Observe the autorouter during the routing process OrCAD Layout SmartRoute User s Guide 43 Chapter 6 Autorouting and batch routing To set up the board for routing using angled directions by layer 1 From the Options menu choose Parameters The Parameters dialog box displays Set the routing layers as follows Top vertical Bottom 45 up Innerl 45 down nner2 horizontal Then if they are listed in the dialog box set the other four layers to Plane once set to plane the layers no longer display in the dialog box Check the other parameter settings in the dialog box then choose the OK button From the Options menu choose Routing Passes The Routing Passes dialog box displays Ensure that all of the routing passes are selected and select the Mitered option from the Track Corners manufacturing pass Choose the OK button From the Auto menu choose Pre Route Synopsis Review the report to ensure that the design parameters are as you would expect then close the report From the Auto menu choose AutoRoute Board Observe the autorouter during the routing process Routing with angled direction by layer
32. areas This is highly desirable but with high density boards not always possible Worst Do not attempt to route a board with one or more very large bright red areas commonly referred to as connection hot spots A large hot spot would encompass 10 20 of the total board area These are problem areas reposition components to reduce the density in these areas Compromise It is virtually impossible to avoid hot spots when designing dense boards However it is possible to reduce their impact Note that several small hot spots are better than one or two large hot spots If you have large hot spots return to Layout Plus and where possible break up the large hot spots into smaller hot spots Or reduce the density in the large hot spots Analyze parameters The Analyze Parameters feature is unique to SmartRoute With this feature you can estimate the routing time and percentage of route completion for the active board using the current parameters With this feature you can conduct what if exercises with the parameter settings trying a number of different configurations The Analyze Parameters option estimates the settings effect on routing time and routing success However if you use non standard parameters for example oversize via pads of 0 075 the accuracy of the prediction may be degraded 58 OrCAD Layout SmartRoute User s Guide Appendix B Solving routing problems AutoRoute Area and AutoRoute Component The AutoRoute
33. art SmartRoute again will only perpetuate the cycle If you answer No the autorouter stops OrCAD Layout SmartRoute User s Guide 61 Appendix C Suggested reference material Duda R O and P E Hart Pattern Classification and Scene Analysis Wiley N Y 1973 Freeman James A and David M Skapura Neural Networks Algorithms Applications and Programming Techniques Addison Wesley Publishing Company 1991 Gelenbe Erol ed Neural Networks Advances and Applications II Elsevier Science Publishers 1992 Huang William Y and R P Lippmann Comparisons Between Conventional and Neural Net Classifiers Proceedings of the First International Conference on Neural Networks IV 85 1987 Kennedy Ruby and Yuchun Lee Benjamin Van Roy Christopher Reed Solving Pattern Recognition Problems 1995 Lee Yuchun and Richard Lippmann Practical Characteristics of Neural Networks and Conventional Pattern Classifiers on Artificial and Speech Problems Advances in Neural Information Processing Systems II Morgan Kaufmann 1990 Lippmann Richard P An Introduction to Computing with Neural Nets Neural Networks Theoretical Foundations and Analysis C Lau Editor 1992 IEEE Press Lippmann Richard P Pattern Classification Using Neural Networks IEEE Communications Magazine pp 47 54 1989 Rumelhart D E G E Hinton and J L McClelland Parallel Distributed Processi
34. ctions than there are power and ground connections Clearance The Clearance option specifies the spacing required between tracks track to track clearance This value is defined in Layout Plus 30 OrCAD Layout SmartRoute User s Guide Chapter 5 Setting up the board for routing Analyzing routing parameters The Analyze Parameters feature is unique to SmartRoute With this feature you can estimate the routing time and percentage of route completion for the active board using the current parameters Furthermore you can conduct what if exercises with the parameter settings trying a number of different configurations The Analyze Parameters option estimates the settings effect on routing time and routing success The more average the board is the more accurate the prediction of routing time and completion for the board The prediction may be off by varying degrees It is most useful as a measure of the effect of changing placements spacing rules and so on To analyze the selected parameters effect on routing 1 From the Options menu choose Parameters The Parameters dialog box displays 2 Choose the Analyze Parameters button The estimated time and completion for the board display at the bottom of the dialog box 3 When you are finished choose the OK button Specifying routing passes In the Routing Passes dialog box you can enable various routing passes that will be used during the autorouting sequence as wel
35. d line that represents the progress of the current routing pass The bottom line provides a snapshot of the current routing status such as the number of connections routed the percentage of the board that s been routed number of remaining connections number of vias number of contentions and total accumulated time on the board including both Layout Plus and SmartRoute activities For many commands the status bar provides help tips For example when you choose the Zoom In command the status bar displays the following message Press and hold at center of zoom area After you press and hold the mouse button the message changes Drag cursor to enclose zoom area When you release the mouse button the status bar displays yet another message Select center of another zoom area The status bar can provide net and pin information too When you choose the Identify Net or Identify Pin commands and select a net or a pin the results of the query display in the status bar And finally the status bar displays information about SmartRoute s current status such as which task it is performing after you choose a command OrCAD Layout SmartRoute User s Guide 13 Chapter 3 The SmartRoute work environment Viewing the board Zoom functions In SmartRoute you can easily view different areas of the board get information about specific pins and nets and find parts pads and locations on the board You can also run a board density check using
36. e a board you should immediately choose the Save As command and save the file with the correct filename Closing a design and exiting SmartRoute To close a design in SmartRoute you must either open another design or exit SmartRoute there is no Close command For information on opening a design see Opening a design in this chapter To exit SmartRoute b From the File menu choose Exit If there are unsaved changes in the design SmartRoute prompts you with the following three options Select the desired option Save and Exit SmartRoute opens the Save As dialog box Choose the OK button SmartRoute saves the design and exits Discard and Exit SmartRoute discards the unsaved changes and exits Resume Program This option cancels the Exit command OrCAD Layout SmartRoute User s Guide 21 Chapter 5 Setting up the board for routing Setting up the board is the most important part of the routing process There are three items to consider when setting up the board for routing in SmartRoute net properties parameters and routing passes When routing a board using SmartRoute the vast majority of setup activities are performed in Layout Plus When you load the board into SmartRoute you are mainly concerned with checking the values displayed to confirm that they reflect what you want This chapter describes each of the following in detail Net properties Confirm and change if desired the net properties that you set in Layou
37. ect all of the routing passes Autoroute the board If the board has more than 10 fanout failure go back to Layout Plus and adjust placement to lessen the density in the areas in which the failures occurred then bring the board back into SmartRoute 32 OrCAD Layout SmartRoute User s Guide Chapter 5 Setting up the board for routing The Routing Passes dialog box ROUTING PASSES Memory Cancel Fan Qut Used SAD Pra Patter oun The routing passes are described below Memory This routing pass routes all memory or memory like nets on the board This pass is heuristic it searches for nets that can be routed using one of several simple patterns OTCAD recommends that you run it even though you may not have actual memory on the board Fan Out Used SMD Pins This pass is used to fanout vias from SMD or edge finger components The fanout via that is usually used is a conventional through hole via The fanout via can change depending on the density of the area being routed If the autorouter does not have enough space for a via it will switch to a smaller one The fanout pass is both heuristic and search It should always be used if there are single sided components on the top layer or bottom layer of the board When a via fails to fanout a small yellow circle with an X in the center displays on the board Note Very dense boards with SMD parts on top and bottom layers may have difficulty during fanout OrCAD suggests that
38. eet To change net properties in SmartRoute 1 From the Options menu choose Net Properties The Net Properties dialog box displays Enter the name of the net that you want to view in the Find Net text box Modify the value for Routing Weight Length Minimize Route Action or Track Width by selecting a new value from the appropriate drop down list For a detailed description of each option read the dialog box option descriptions below 4 Choose the OK button Note OrCAD recommends that you use the net property values received from Layout Plus Example In this example you modify the net properties for a four layer board in which two layers top and bottom are used for routing signal connections and two planes are reserved for the power and ground nets When signal connections are to be routed and power and ground are to be reserved for planes set the power VCC and ground GND nets as planes using the Route Action option in the Net Properties dialog box 1 In the Find Net text box type GND to find the ground net N In the Route Action column note the available options For this example you want the GND net to be fanned out as for a plane therefore select the Fanout Plane option Repeat steps 1 and 2 for the VCC net Choose the OK button 24 OrCAD Layout SmartRoute User s Guide Chapter 5 Setting up the board for routing The Net Properties dialog box JJ n LU JF RI X I RDS A
39. ers will start over routing interactively from scratch To help ease the frustration of routing the remaining few connections left by the autorouter SmartRoute uses contention routing This allows the autorouter to route connections if necessary regardless of spacing conflicts or contentions during the initial routing pass Then SmartRoute removes the contentions in subsequent passes At the end of the autorouting sequence on an extremely dense board there may sometimes be a few contentions that will require interactive cleanup Is it better to have an unrouted connection or a routed track with a contention Experienced designers prefer the track be routed with the contention rather than being left unrouted This is because the contention is normally confined only to one area along the track and it is easier to resolve a problem in one area than to make room for an entirely unrouted connection Routing quality is somewhat different from routing time and routing power in that it is evaluated in both subjective and objective terms that is you may consider measurable criteria as well as aesthetic criteria when evaluating the quality of a routed board The measurable criteria include total number of vias total amount of copper tracks average track length wandering or long tracks violation of direction by layer settings absence of acute angles and equal spacing of tracks between pads OrCAD Layout SmartRoute User s Guide 5 Chapter 1
40. et is ignored by the autorouter Locked When Locked is selected the routed connections in the net cannot be rerouted pushed or shoved Partially routed connections may sometimes still be shoved Fanout Route The net is fanned out from an SMD or edge finger pad then routed Fanout Plane The net is fanned out from the edge finger or SMD pad but left in an unrouted state used for connecting to power and ground planes Track Width The default entry is the primary track width as set in Layout Plus OrCAD recommends that you do not change this value but if you wish to change it select a new width from the drop down list If the width of a net is too thick to exit a pad SmartRoute will use the net width from a standard set of net widths in SROUTE INI that is less than or equal to the width of the pad SmartRoute will not drop the width of the net lower than the minimum width for the net specified in Layout Plus Tip If you need a width that isn t shown in the list you can add it to SROUTE INI in the section Legal Track Widths 26 OrCAD Layout SmartRoute User s Guide Chapter 5 Setting up the board for routing Setting parameters After the net properties have been set set the design parameters There are three categories of parameters They are all controlled in the Parameters dialog box Layers Design parameters Analyze parameters To change the parameters for routing 1 From the Options menu choose Paramete
41. eter review Review the parameters to ensure that they are complementary For example a 55 mils via with 6 mils track and 6 mils clearance is a mismatch the via is inappropriately large for the track size that will greatly handicap the autorouter on a dense board Use the following as a guide when selecting parameters Tracks Clearance mils Pads Through hole Pads SMD Vias 12 13 55 60 24 55 60 10 10 50 55 24 55 60 8 8 50 24 35 40 6 6 48 50 24 30 35 Fine Pitch SMD 6 6 48 50 10 28 35 Design and manufacture parameter guidelines OrCAD Layout SmartRoute User s Guide 57 Appendix B Solving routing problems LI Component placement Assuming the parameter settings are reasonable and the board can indeed be routed it may be necessary to adjust part placement SmartRoute has three excellent aids for use in evaluating placement Density graph Analyze parameters Area or component autoroute See For information on component placement strategies see Component placement strategies in this appendix Density graph SmartRoute s density map accessible from the View menu is extremely accurate and can be useful in identifying problem areas The colors of the density map vary from blue low density to bright red high density This density map is the primary indicator of routing order Use the following as a guide for use in evaluating the density map Best The best board layouts display no red high density
42. has important advantages including fewer vias shorter track length and higher completion percentage In addition it facilitates interactive editing Note that SmartRoute will choose the directions for angled routing if you don t specify them Use the following as a guide for angled routing for four and six layer boards Four routing layers Top Horizontal or vertical Inner 1 45 up 1 o clock or 2 o clock Inner 2 45 down 4 o clock or 5 o clock Bottom Horizontal or vertical different from top Six routing layers Horizontal or vertical For all inner layers on a board with six routing layers 45 up down 1 o clock 2 o clock 4 o clock or 5 o clock Horizontal or vertical different from top h3 Note Do not use all 45 up and 45 down use a mix of 45 and clock angles 44 OrCAD Layout SmartRoute User s Guide Chapter 7 Editing the board You can use the interactive and manual routing commands on the Auto and Tool menus to manually route areas of the board and for general board editing Use these commands when you want more control over the routing process than is possible with the autorouter For example with the interactive and manual routing commands you can a Autoroute individual connections defined areas or the connections associated with a single component Draw a path for the autorouter to follow using SketchA Track Route a track manually under design rule check DRC supe
43. her hand uses an advanced sequencing cost that varies from board to board and takes the board s connectivity into account Considerations also include the priority of nets various patterns requiring a specific routing order busses widths of tracks and connection density Shape based routing has replaced gridded routing in today s autorouters Conventional shapes provide immense advantages in routing speed and in routing flexibility however conventional shapes and shape based routing do not address routing quality The SmartRoute neural shape concept successfully addresses the issue of routing quality Specifically the SmartRoute neural shapes consist of polygons of all different sizes and shapes This together with routing algorithms that permit X and Y routing 45 routing and that are capable of selecting a routing direction by layer from multiple choices horizontal vertical 45 up 45 down 1 o clock 2 o clock 4 o clock and 5 o clock provide the flexibility to enhance routing quality Routing algorithms passes SmartRoute includes algorithms called passes for heuristic routing a problem solving technique in which the most appropriate solution of several found by alternate methods is selected in successive passes of the router two layer power and ground routing memory routing fanout dispersion routing several different pattern routing algorithms push and shove routing and rip up routing All algorithms are driven
44. hoose the OK button h3 Note During autorouting the status bar contains three levels of information about the routing passes The top level contains the names of the seven passes of the autorouting sequence As routing progresses the pass that SmartRoute is currently executing is red The next level is a red line that represents the progress of the current routing pass The third level is the text that displays beneath the red line This text provides information about the status of the autorouting sequence Summary On very dense SMD boaras run the fanout routing pass alone before autorouting with all of the passes If you experience more than 10 fanout failure adjust placement in Layout Plus Otherwise autoroute the board using all of the available routing passes Example In this example you are routing a very dense four layer SMD board You need to run Fan Out Used SMD Pins first If you have less than 1096 fanout failure you can autoroute the board 1 From the Options menu choose Routing Passes The Routing Passes dialog box displays Select the Fan Out Used SMD Pins option and deselect all other routing passes in the dialog box then choose the OK button From the Auto menu choose AutoRoute Board SmartRoute performs fanout Check the board to see that you have less than 10 fanout failure A failure is indicated by a small yellow circle with an X in the center fso open the Routing Passes dialog box Sel
45. ign rule errors the errors can be detected in Layout Plus before loading the design into SmartRoute From Layout Plus s Auto menu choose Design Rule Check select all the options in the Check Design Rules dialog box that displays then choose the OK button Another worthwhile design check to perform in Layout Plus is to display all items on the board i e component pads board outline connections copper and so on and visually inspect them for obvious errors such as connected pads outside the board outline OrCAD Layout SmartRoute User s Guide 53 Appendix A Design checklist and common errors Use the following checklist as a guide for avoiding design errors in SmartRoute Do not try to subdivide plane layers with copper outlines or details until after routing Avoid placing copper lines outlines or details on routing layers in an attempt to restrict routing to the areas created Copper area obstacles may be placed on routing layers for the purpose of prohibiting SmartRoute from placing tracks or vias in the area defined by the copper Note that SmartRoute maintains spacing around text on copper layers Route keepout obstacles may be placed on routing layers for the purpose of prohibiting the placement of routes in the area defined by the obstacle Component pads outside the board outline to which connections are attached will be rejected Hence before attempting to load a board design into SmartRoute visually inspect
46. in order to put in a via The circuit density number of connections is far in excess of that which will fit on the area and number of routing layers selected for routing Upon returning to Layout Plus a design rule check of the routed board finds errors Most likely you changed the parameters primary pad via width primary track or clearance in the Parameters dialog box in SmartRoute and used these new parameters during autorouting You must manually set the new parameters in Layout Plus Also if there are unresolved contentions in SmartRoute they are flagged as errors in Layout Plus See For a description of the options available in the Parameters dialog box see Setting parameters in Chapter 5 Setting up the board for routing SmartRoute displays the following message LOW RESOURCES You may encounter this message while performing activities such as board editing You will not encounter it during autorouting This is the result of the combination of the board s characteristics and the editing having prevented some memory from being realized A few occurrences are not of concern However if it happens several times 6 to 8 you should clear your computer s memory by saving the MAX file using SmartRoute s Save As command exiting all programs and restarting Windows If you are routing a board that is near the limit of available memory and you have noticed this Low Resources message two or three times you may w
47. ined that autorouted boards do not provide the same quality as manually routed boards The side effects of autorouting can include too many vias tracks that wander vertical layers with too many horizontal segments and vice versa unevenly spaced tracks and more The most common complaint however is that autorouters usually route using an X Y orthogonal strategy Experienced board designers instinctively route using diagonals Diagonal routing is more aesthetically pleasing and allows for more track segments to be placed in an area Consequently the probability of finishing a more difficult board is increased with diagonal routing This chapter examines the new technologies and time proven methods that SmartRoute uses to tackle autorouting quality issues Neural networks A neural network is a subset of artificial intelligence SmartRoute uses a neural network for routing intelligence and time and completion projection It is among the first CAD software products to employ artificial intelligence A neural network analyzes problems for which there is no explicit solution Instead there may be a variety of solutions some better than others Consider an analogy There are a variety of ways a board can be routed some of which are better than others The designer selects the best solution considering all the options and possible outcomes This is also the function of the neural network and the other neural utilities in SmartRoute to provide
48. ing autorouting The pull down menus include File Edit View Tool Options Auto and Help Their functions are as follows File menu The File menu includes commands for opening closing and saving designs as well as backup and restoration commands See For information on opening closing and saving designs see Chapter 4 Opening and saving designs Edit menu The Edit menu includes the Undo and Redo commands and a Find Goto command View menu The View menu includes commands for viewing board density clearing and redrawing the screen and various zooming commands LL See For information on zooming and searching in SmartRoute see Viewing the board in this chapter Tools menu The Tools menu includes commands for highlighting and identifying nets identifying pins sketching an approximate track for SmartRoute to follow and manually routing OrCAD Layout SmartRoute User s Guide 11 Chapter 3 The SmartRoute work environment Options menu The Options menu includes routing setup commands such as Net Properties Parameters and Routing Passes It also includes the Backup Interval command with which you can set the duration between automatic backups There is also a Batch Setup command for setting batch routing options and the Hints Checkbox command for enabling or disabling the SmartRoute new user hints feature LL See For information on setting up the board for routing see Chapter 5 Setting up the board
49. ing a design ziocenttee re v a 19 Savine a desigri iini e UD RE DORDOGNE e ERE USA 20 Using backup o2 ihngenitestetetee ote te itte ee e E 20 Closing a design and exiting SmartRoute eese 21 Setting up the board for routing 23 Setting net properties oo ca eg ee t eto rr nan 24 K T parameters ES 27 IV Ds 28 Design paratneters iin d c et a B i et iie A dee 29 Analyzing routing parameters sees ee ee eee eee 31 Specifymg ro ting passes oot ete Rr a 31 Gro ITO 34 Manufacturing passessi pei r oaeee hu 35 Autorouting and batch routing sse 37 ANULOTOUCIDE siio a topo A o a LO ba nr 37 Pre route Synopsis in sesh ln nn tee ens 38 Running the autorouter esses eene nennen nennen ene 38 Batch Toutin gis ees eee aU ai ee nie aeree 40 Setting up and routing two layer Boards sss esse sese eee ee eee 41 Setting up and routing multilayer boards eese 42 Setting Up the l yersa s se ee RU S RR SERT Ede 43 Editing the board inii conici ihe Uc eLIpu lubi un dako cu 45 Inter ctive TOUTING assisted Ati UR en petu eran a ERREUR 46 AutoROUte AT63 oi hn N Stir etn te i etes 46 AutoRoute Component eera e E r E nennen nennen 46 AutoRoute I 2 nne ime e P ee RU AE E EEE EES ESEE iS 46 AutoRoute One cp t meter ee e e etis 47 SketchA Track TOUN s e e EL e IER He P Re t e egets 48 Manual routing 4
50. izontal and vertical segments The routing time will be somewhat less than it would be using a primary direction that is not either horizontal or vertical Angled direction by layer If routing speed is not a major consideration for you you can use angled direction by layer Angled direction by layer results in shorter tracks and fewer vias It can route tracks in a combination of angles 45 up 45 down 1 o clock 2 o clock 4 o clock and 5 o clock For example on a four layer board you may choose to use vertical 45 up 45 down and horizontal The first of the next two processes emphasizes routing speed using vertical and horizontal routing The second process demonstrates angled direction by layer You can use BOARD3 MAX in the LAYOUT SAMPLES DEMOSR directory for this operation To set up the board for horizontal and vertical routing 1 From the Options menu choose Parameters The Parameters dialog box displays 2 Set the four routing layers top bottom inner1 and inner2 as Vertical Horizontal Vertical Horizontal by selecting the appropriate options from the drop down lists Then if they are listed in the dialog box set the other four layers to Plane once set to plane the layers no longer display in the dialog box Check the other parameter settings in the dialog box and choose the OK button 3 From the Options menu choose Routing Passes The Routing Passes dialog box displays 4 Ensure that all of the routing passes
51. ks are not Plus prior to starting Placed on layers 2 and 3 Also the design loaded as a four layer board from Layout SmartRoute it is Plus is returned to Layout Plus with layers 2 and 3 reserved for plane activity possible to modify the layer routing direction 1 From the Options menu choose Parameters The Parameters dialog box bias inside displays SmartRoute For layer 2 select Plane Layer 2 is reserved for use as a plane layer For layer 3 select Plane Layer 3 is reserved for use as a plane layer For the top layer select Horizontal from the drop down list The top layer of the board will be routed with a horizontal bias 5 For the bottom layer select Vertical from the drop down list The bottom layer of the board will be routed with a vertical bias Design parameters Parameters are read directly from Layout Plus In the Parameters dialog box you can check the parameters you set in Layout Plus including units pad and via width track width and clearance to make sure they display as you expect Before the new parameter settings are accepted in SmartRoute you must choose the OK button in the Parameters dialog box and respond to the questions that display The answers you provide confirm your decision to modify parameters before the changes are accepted by SmartRoute h3 Note Always check the Primary Pad Via Width Primary Track and Clearance parameters to make sure that the values displayed are what you wo
52. l as set options for manufacturing OrCAD strongly recommends that you run all the passes using the default routing pass setup without modification However there are some instances in which only one or more of the routing passes should be activated You have a very dense SMD board and you are not sure that all of the pads will be fanned out with the current placement In this situation select only Fan Out Used SMD Pins and deselect the other routing passes When you autoroute the board only the Fan Out Used SMD Pins routing pass is performed Fanout failures are marked with a small yellow circle with an X in the center If there are many failures you should change the placement on the board You have a true memory bank on your board and you are concerned with where it should be placed and how the components should be oriented In this situation select only the Memory routing pass to evaluate the memory pattern Before the routing passes are run SmartRoute analyzes the board During this phase the board is scanned and the appropriate neural costs are applied by the neural network Once this is finished the specified routing passes are performed OrCAD Layout SmartRoute User s Guide 31 Chapter 5 Setting up the board for routing To specify routing passes 1 From the Options menu choose Routing Passes The Routing Passes dialog box displays Ensure that the passes you want to run during autorouting are selected then c
53. nces For example SHIFT F1 means to hold down the SHIFT key while pressing Fl ALT F A means to press and release each of these keys in order first ALT then F then A Arrow keys is the collective name for the UP ARROW DOWN ARROW LEFT ARROW and RIGHT ARROW keys To choose a command from a menu you can use the mouse or press a key combination For example from the File menu choose Open ALT F O OrCAD Layout SmartRoute User s Guide V About this manual Text Text you are instructed to type is shown in bold For example if the manual instructs you to type max you type an asterisk a period and the lowercase letters max The text you type is usually shown in lowercase letters unless it must be typed in uppercase letters to work properly Placeholders for items such as filenames that you must supply are shown in italic For example when the manual directs you to type cd directory name you type the letters ed followed by a space and the name of a directory For a directory called CIRCUITS you would type cd circuits Examples of syntax and report output are displayed in monospace font for example 17 74ALS163 U5 U6 vi OrCAD Layout SmartRoute User s Guide Chapter 1 About SmartRoute Autorouters have two primary objectives to route boards to 100 completion and to route boards quickly SmartRoute adds a third objective guality of routing Historically professional board designers have compla
54. ng Volume I MIT Press Cambridge MA 1986 OrCAD Layout SmartRoute User s Guide 63 A algorithms routing 3 23 31 33 Fan Out Used SMD Pins 31 33 Memory 33 Pattern 33 Push N Shove 34 Ripup 34 Analyze Parameters feature 3 58 Analyze Parameters routing pass 37 angled direction by layer 43 44 arcs 9 area routing 46 59 Auto Backup Interval dialog box 20 Auto menu 7 2 AutoRoute Area command 46 59 AutoRoute Batch command 40 AutoRoute Component command 46 59 AutoRoute Net command 46 AutoRoute One command 47 autorouting 37 39 autorouter stopped 55 batch routing 40 completion percentage 56 57 multilayer boards 42 44 slow 56 57 speed of 56 57 two layer boards 47 B backing up your design 20 Backup Interval command 20 batch autorouting 40 Batch Design File dialog box 40 board density 16 58 59 board outlines 54 Index C center board 14 changing layers 48 Channel parameter 30 channels 30 59 clearance 30 Clearance parameter 30 closing designs 21 commands AutoRoute Area 46 59 AutoRoute Batch 40 AutoRoute Component 46 59 AutoRoute Net 46 AutoRoute One 47 Backup Interval 20 Density Graph 16 58 Exit 27 Find Goto 17 Highlight Net 7 Hints Checkbox 13 Identify Net 7 Identify Pin 7 Manual Route 50 Net Properties 24 Open 19 Parameters 27 Pause AutoRouter 37 Pre Route Synopsis 37 36 Redo 45 Restart AutoRouter 37 Routing
55. nout is not as effectively controlled in SmartRoute as it is in Layout Plus You cannot tell the router to go only to the interior or exterior of a component nor can you specify whether to share fanout vias or not SmartRoute is share only If there are unrouted connections or there are contentions after autorouting try disabling the fanout memory and pattern routing passes and running the autorouter again See For information on enabling or disabling routing passes see Specifying routing passes in Chapter 5 Setting up the board for routing If you get an out of memory error when your board is nearly routed it may be possible to finish the routing process Save the design reload it and run the routing process again To save time turn off the fanout memory and pattern routing passes If the status bar in SmartRoute reports that there are contentions on the board after routing run Design Rule Check in Layout Plus From Layout Plus s Auto menu choose Design Rule Check In the Check Design Rules dialog box that displays select the Route Spacing Violations option then choose the OK button Occasionally within the first ten minutes of autorouting SmartRoute reports the following error Routing Problem encountered Attempt auto resume If you answer Yes the program attempts to restart But if upon restarting the message displays again immediately SmartRoute is caught in an infinite loop and answering Yes to rest
56. nro etri deret nn e peres 1 Neutral Costs o ha 3 Neural shapes 2 il nl hn an ate pie 3 Routing algorithms passes sees ee eee eee 3 Angled direction by layer e mem he d e u hn 4 Routing time power and quality sees sees 5 ROUEITS time iii ee e Reed nn pep 3 Routing DOWeLE i t t a dd er eret aa eee 5 Routing quality Reo a ei RON 5 Predicting routing time and percent of completion sese 6 Chapter 2 Getting Started uenit a rri enn o 7 Cahlibrating Sm rtRoute 2 2 2 EL pire HR E Ee peto rS DEP Raro Penes 7 Starting SmartRoute one edes Reo ipo al thence deus 8 The SmartRoute session frame essent eene eene trennen enne 8 Compatibility with Layout Plus eese eene ennemi 9 Mery caelo ti Ai eo e bua ineo be nde ipe 9 Chapter 3 The SmartRoute work environment 11 SmaitRoute menus nette ert oa 11 N w user hints eiecit eR e ee eite E epe etie ries 13 The st t s b rzz u rta e IE ERR ER SURFING EHE eR 13 Viewing the board sri ne ime terre tere he erede es 14 VA vierte Mo I zos r nn 14 Displaying the board density sese 16 Getting information seiiet arie enpi eirean raires E a nR iera 17 OrCAD Layout SmartRoute User s Guide iii Contents Chapter 4 Chapter 5 Chapter 6 Chapter 7 Appendix A Appendix B Appendix C Opening and saving designs nna 19 Open
57. nsity map displays Use the following as a guide for evaluating the density map Best The best board layouts display no red high density areas This is highly desirable but with high density boards not always possible Worst Itis difficult perhaps impossible to route a board with one or more very large bright red areas commonly referred to as connection hot spots A large hot spot could encompass 10 to 20 of the total board area These are problem areas reposition components to reduce the density in these areas Compromise It is virtually impossible to avoid hot spots when designing dense boards However it is possible to reduce their impact Several small hot spots are better than one or two large hot spots If you have large hot spots return to Layout Plus and where possible break up the large hot spots into smaller hot spots Or reduce the density in the large hot spots To exit the density map a From the View menu choose Redraw Screen 16 OrCAD Layout SmartRoute User s Guide Chapter 3 The SmartRoute work environment Getting information Use the Find Goto command on the Edit menu and the Highlight Net Identify Net and Identify Pin commands on the Tools menu to locate or obtain information on the nets and pins in the design To find a component pad or location on the board 1 From the Edit menu choose Find Goto The Find dialog box displays 2 Perform one of the following tasks To find a part en
58. o unroute all tracks that are in contention so that you can reroute them When SmartRoute is finished unrouting these tracks the number of connections that were unrouted displays in the status bar See For information on contention see Contention in Chapter 5 Setting up the board OrCAD Layout SmartRoute User s Guide 51 Appendix A Design checklist and common errors In preparing a Layout Plus file for SmartRoute it is not uncommon to find unexpected design criteria violations which can be catastrophic If the autorouter does not detect the errors it may spend a considerable amount of time routing the board vet the results will be unusable In order to prevent such a situation SmartRoute reads and writes Layout Plus files directly During this process SmartRoute searches for design rule errors Typical design rule errors include a connected component pad overlapping shorting out a component pad of a second component thus tying two nets together or a connected component pad to which a thick track is attached If this component pad is too close to a different net it creates a space violation These design rule errors are not detected during the loading process Instead they are detected at the time the autorouter is started If violations are detected the autorouting process stops and a message displays In this situation examine SROUTE LOG for the offending error and correct it h3 Note In most designs with des
59. oard check that the layer settings in the Net Properties dialog box are correct Most importantly in the Net Properties dialog box set the Route Action for power and ground nets VCC and GND to Route not Fanout Plane as with multilayer boards SmartRoute has a power and ground router that creates an optimum pattern for power and ground nets This pattern attempts to place the power and ground tracks inside the row of pins of an IC on the layer coincident with the direction of the IC major axis For example consider a board on which the ICs are vertically biased the top layer is horizontally biased and the bottom layer is vertically biased Power and ground will be placed on the bottom layer and will run vertically inside the rows of pins on each IC The top layer will contain horizontal tracks that connect together the vertical tracks inside the rows of IC power and ground To set up and route a two layer board 1 From the Options menu choose Net Properties The Net Properties dialog box displays 2 Find the power net and change the Route Action option to Route Repeat this step for the ground net then choose the OK button Seealso For more information on setting net properties see Chapter 5 Setting up the board for routing 3 From the Options menu choose Parameters The Parameters dialog box displays 4 Check the layer settings to ensure that the top layer displays with a horizontal bias and the bottom layer displays
60. of Electronics stocks NYSE closing prices on leading computer manufacturers stocks and so on Additionally you might want to include economic factors such as the prime rate the Eurodollar Dmark Yen and so on Finally and surprisingly you might want to include some seemingly unrelated variables such as new housing starts The neural network analysis attempts to identify relationships among the various variables and the item whose price is being predicted A direct relationship such as the price of crude oil and an oil company is obvious An indirect relationship is not as obvious for example the change in the closing price of a fast food chain and the lower than average seasonal rainfall in the coffee growing regions of South America The point is that in a relatively short period of time a neural network can find direct and indirect associations Just as a neural network for financial analysis requires training the SmartRoute neural network also required training This training consisted of presenting to SmartRoute a large number of routed boards that were routed interactively by experienced professional board designers These boards contained examples of every technology used today such as single layer two layer multilayer DIPS SMD PGA BGA and so on with the densities and sizes that are characteristic of today s packaging technologies The boards selected had all the characteristics associated with quality routing such as
61. ommand to route all of the connections originating or ending on a pin of a component Note that within a net only the connections starting or ending on the selected component will be routed To autoroute the connections originating or ending on a pin of a component 1 From the Auto menu choose AutoRoute Component The pointer becomes a vertical arrow 2 Select a component The connections starting or ending on a pin on the component are automatically routed Using the AutoRoute Net command you can route all of the connections associated with a net To autoroute the connections associated with a net 1 From the Auto menu choose AutoRoute Net The pointer becomes a vertical arrow 2 Select a connection within the net All of the connections within that net are routed 46 OrCAD Layout SmartRoute User s Guide Chapter 7 Editing the board AutoRoute One The AutoRoute One command autoroutes one connection at a time To autoroute one connection 1 From the Auto menu choose AutoRoute One The pointer becomes a vertical arrow Place the pointer over any connection to be routed and click the left mouse button Repeat step 2 for each connection that you want to route OrCAD Layout SmartRoute User s Guide 47 Chapter 7 Editing the board SketchATrack routing Using the SketchATrack command you can sketch a suggested path and the autorouter routes the connection approximately matching the path you have sketched
62. op level contains the names of the seven passes of the autorouting sequence As routing progresses the pass that SmartRoute is currently executing is red a The middle level is a red line that represents the percentage of completion 38 OrCAD Layout SmartRoute User s Guide Chapter 6 Autorouting and batch routing The bottom level provides a snapshot of the current routing status such as the number of connections routed the percentage of the board that s been routed number of unrouted connections number of vias number of contentions routing time and total accumulated time on the board including both Layout Plus and SmartRoute activities With the exception of number of contentions this is a real time display and alleviates the need for pausing the autorouter for detailed information Note The number of contentions displays in the status bar During routing the number of yellow circles contentions on the board may differ from the number shown in the status bar This is due to the fact that the screen is updated instantly as a connection is routed whereas the data line is updated only after a major routing pass To autoroute the board o From the Auto menu choose AutoRoute Board SmartRoute initiates the autorouting sequence specified in the Routing Passes dialog box Note As the router progresses tracks may display small jagged steps SmartRoute automatically runs a pass that cleans up tracks and minimizes vias d
63. outing to save time To run the pre route synopsis 1 From the Auto menu choose Pre Route Synopsis 2 Review the data in the report that displays then close the report Running the autorouter The first routing pass in the autorouting sequence is called Analyze Board This process involves SmartRoute s neural network discussed in Chapter 1 About SmartRoute The neural network studies the various parameters and characteristics of the board and compares them to those it was trained with The bigger the board the longer the Analyze Board pass takes A small unrouted board may spend about 90 seconds on this pass A large multilayer routed board may spend two to four minutes on this pass The Analyze Board pass creates a neural map and selects a neural cost file Following the Analyze Board pass the autorouter progresses sequentially through the routing passes specified in the Routing Passes dialog box You can observe the following during autorouting The fanout of edge finger connectors and SMD pins during the Fan Out Used SMD Pins pass The routing of the memory array on the board during the Memory pass The remaining signal connections on the board are routed with a combination of orthogonal and diagonal segments Although the power and ground nets are fanned out from the I O connector they are not routed During routing the three levels of the status bar provide information about the autorouter s status The t
64. ow heavily connected the part is and the presence of top and bottom layer SMD pads occupying the same space Use the following table as a guide for achieving adequate SMD separation Board characteristics Fanout allocation Small SMD 16 20 pins lightly One or two rows of fanout vias connected between parts Medium SMD heavily connected Minimum of two rows of fanout vias Large SMD 2150 pins heavily Three to four rows of fanout vias connected Large SMD 2150 pins heavily Six or more rows of fanout vias connected SMD parts on the top and bottom layers Very large fine pitch SMD 2150 pins Eight or more rows of fanout vias heavily connected Parts on both the top and bottom layers in same area Suggested fanout allocations The above assumes two things about the fanout router It can fanout vias to both the outside and inside of the SMD component It has both heuristic simple pattern algorithms and search capabilities that can find a fanout via when necessary SMD location on top and bottom layers In today s high density designs the SMDs on both top and bottom layers may be large and can be in excess of 300 pins The previous section discussed the spacing between SMD parts on a layer You must also consider the relationship between parts on different layers To maximize the board area available for fanout vias place components on the bottom layer directly under components on the top layer In effect the p
65. play 1 From the View menu choose Zoom Center 2 Position the pointer at the location you want to center in the display and click the left mouse button The selected area moves to the center of the display The scale remains unchanged 3 Press the ESC key to exit zoom mode To view the whole board in the display 1 From the View menu choose Zoom All Fit The entire board is displayed on the screen 2 Press the ESC key to exit zoom mode Z Tip You can also use SmartRoute s shortcut keys to change the current view of the board Press I to zoom in press O to zoom out or press Z to center the view around your current pointer position OrCAD Layout SmartRoute User s Guide 15 Chapter 3 The SmartRoute work environment Displaying the board density The Density Graph command displays an extremely accurate color coded graphical density map of the board with red representing the hottest or most dense areas and blue representing the least dense The density graph considers unrouted connections routed segments and pads to calculate density It provides you with a detailed analysis of routing density due to component placement When you are working with SmartRoute you should use SmartRoute s density graph rather than Layout Plus s because Layout Plus s density graph is not optimized to provide the information valuable to SmartRoute To display board density b From the View menu choose Density Graph The color coded de
66. r selection 12 OrCAD Layout SmartRoute User s Guide Chapter 3 The SmartRoute work environment New user hints The status bar A number of SmartRoute menu commands provide a SmartRoute L New User Hint feature called New User Hints The hints consist of command and dialog Routing Passes box descriptions and tips Use the hints PITTI PASSES aH yii d a caulamize Te auleraubg as a learning tool to help you become Selene oo well b ones d familiar with SmartRoute After you el ORE an check os is 5 for desired auer pes have become familiar with SmartRoute and no longer need the hints you may disable them individually or all at once To disable one hint select the Click to turn off hint message option in the hint window then choose the OK button To disable all hints choose Hints Checkbox from the Options menu In the dialog box that displays select the Turn Hints OFF option then choose the OK button The status bar located at the bottom of the session frame displays information appropriate to the activity you are performing ENG O MENACE EE e P H Pr Routed 286 10096 Vias 30 No contentions Total Time 00 01 32 During autorouting the status bar contains three levels of information The top level contains the names of the seven passes of the autorouting sequence As routing progresses the pass that SmartRoute is currently executing is red The middle level is a re
67. r s Guide manual 50 multilayer boards 42 44 net properties 23 nets 26 46 non orthogonal 4 order 25 orthogonal 43 parameters 25 passes 3 31 33 percentage of completion predicting 6 31 58 power 5 predicting routing time 31 58 problems 55 56 quality 1 5 reversal 51 spacing 56 status 3 time 5 31 tips and tricks 67 troubleshooting 55 56 two layer boards 47 using SketchATrack 48 routing passes 23 Analyze Parameters 37 Fan Out Used SMD Pins 31 33 Memory 33 Pattern 33 Push N Shove 34 Ripup 34 Routing Passes command 32 Routing Passes dialog box 32 33 Routing Weight property 25 S Save As command 20 Save As dialog box 20 Save Routed Design File As dialog box 40 saving designs 20 screen in SmartRoute 8 13 session frame amp shape based routing 3 55 Index SketchATrack changing layers 48 circuitous paths 49 command 48 49 creating vias 49 deleting tracks 48 modifying segments 49 slow autorouter 56 57 SmartRoute exiting 21 menus 12 spacing 60 problems 56 tracks 35 violations 54 speed of autorouter 56 57 SROUTE LOG 37 40 53 Start Batch dialog box 40 status bar 13 Stop AutoRouter command 37 stopped autorouter 55 strategies placing components 59 routing 61 subdividing plane layers 54 suggested reading 63 system requirements 9 55 56 T text 24 time counter stopped 55 time for rou
68. rom the Auto menu If you want to stop the autorouting process choose the Stop Autorouter command from the Auto menu If you choose the Stop AutoRouter command you must choose the AutoRoute command of your choice to restart the autorouter which begins at the first enabled pass again Caution Occasionally after the autorouter is started and the Analyze Board pass is completed the autorouter stops and displays this message One or more connections cannot be routed The Analyze Board routing pass checks for critical problems in your design problems that may result in an unusable board The autorouter stops so that you can correct the problem before proceeding The error can be identified by examining the file SROUTE LOG Usually the problem involves a pad and its location in relation to another pad the board outline or other obstacle You should correct the condition in Layout Plus if necessary and proceed OrCAD Layout SmartRoute User s Guide 37 Chapter 6 Autorouting and batch routing Pre route synopsis The pre route synopsis is a report that gives you complete details of the various parameters of the design as well as how you have set up the routing passes that the autorouter will use Use it immediately after you have set up the autorouter but before you start routing Using the pre route synopsis you can preview all of the necessary settings for the router and if they are not set properly you can fix them before r
69. rs The Parameters dialog box displays 2 To bias the direction for routing on each layer select the desired option from the drop down list adjacent to the layer name LL See For information on the layer options in the Parameters dialog box see Layers in this chapter 3 Change the parameters for Units Via Type or Channel by selecting the appropriate options from the drop down lists 4 Change the parameters for Primary Pad Via Width Primary Track or Clearance by typing new values in the text boxes Note OrCAD recommends that you set the parameter values in Layout Plus and then start SmartRoute For more information on parameters see Design parameters in this chapter 5 Choose the Analyze Parameters button SmartRoute analyzes the effects of the parameters that you set and displays the results at the bottom of the dialog box LL See For information on using the Analyze Parameters tool see Analyzing routing parameters in this chapter 6 When your parameter settings are as desired choose the OK button OrCAD Layout SmartRoute User s Guide 27 Chapter 5 Setting up the board for routing Layers The Parameters dialog box Ertmds dre parceri nga Eniri apud nig Beret The Layers group box lists the copper layers as defined in Layout Plus You can select a direction in which routing will be biased for each layer The choices are listed below Best Choice SmartRoute selects the direction for the
70. rs the most control over routing The Manual Route command does not use the SmartRoute autorouter Instead you drag the track along the intended path in a completely interactive fashion SmartRoute s automatic design rule check DRC alerts you to spacing violations by displaying small yellow circles Because SmartRoute allows contentions to exist on the board you can choose to ignore the violations To manually route a track in SmartRoute 1 2 From the Tools menu choose Manual Route Position the pointer over the first pin or connection line and click the left mouse button to select the connection Move the pointer toward the target pad A dashed line in the color of the active layer displays To create a corner click the left mouse button Then continue drawing by moving the pointer in the desired direction The new segment can be either orthogonal or diagonal To insert a via move the pointer to the desired location and type the number that corresponds to the target layer A via symbol white circle is placed at the location and the target layer is displayed If the via symbol is not displayed immediately it will be displayed after the next corner is placed or after choosing Finish from the pop up menu To delete the last portion of track that was routed choose the Undo command from the pop up menu To complete the track at its end pin or on another routed track position the pointer very near the center of the pad or tr
71. rvision that alerts you to spacing violations but permits violations if you concur Unroute the entire board a net a connection or a single segment When using the interactive and manual routing commands SmartRoute features multi level Undo and Redo commands The Undo command reverses the last action taken and has unlimited levels from the last time you saved the design For example if you manually route a horizontal segment then route a diagonal segment and choose the Undo command the result of the diagonal routing is returned to its previous state If you choose Undo again the result of the horizontal segment is returned to its previous state The Redo command reverses the actions of the Undo command OrCAD Layout SmartRoute User s Guide 45 Chapter 7 Editing the board Interactive routing AutoRoute Area There are four interactive routing commands that are actually autorouting commands that route only portions of the board They are AutoRoute Area AutoRoute Component AutoRoute Net and AutoRoute One The AutoRoute Area command routes a selected area on the board To autoroute a selected area on the board 1 From the Auto menu choose AutoRoute Area The pointer becomes a vertical arrow 2 Pressing the left mouse button drag the pointer to select the area to be routed All connections starting or ending in the designated area are routed AutoRoute Component AutoRoute Net Use the AutoRoute Component c
72. sed and release it If your CONFIG SYS file has a device command for RAMDRIVE it may be using too much memory Temporarily reduce this amount by typing REM at the beginning of the line Reboot Windows When you are done using SmartRoute you can restore your RAM drive to its original size If your CONFIG SYS or AUTOEXEC BAT files load SmartDrive it may be using too much memory Temporarily reduce this amount by typing REM at the beginning of the line Reboot Windows If these changes do not bring your available memory to within two or three megabytes of active memory something else is being loaded Use a memory usage utility to determine where the memory is being used and then free up the memory Alternatively you can purchase more memory OrCAD Layout SmartRoute User s Guide 9 Chapter 3 The SmartRoute work environment This chapter describes the things you need to know to find your way around in SmartRoute It describes the functions of the pull down menus and the pop up menus explains what the information that is displayed in the status bar and discusses SmartRoute s new user hints feature It also discusses the zoom functions and query tools used in SmartRoute SmartRoute menus SmartRoute s commands are located on pull down and pop up menus SmartRoute menus are active even when autorouting is in progress and the hourglass is active although some commands are dimmed and unavailable for selection dur
73. signs This chapter explains how to open designs SmartRoute only reads Layout Plus MAX files how to save them using the Save As and Backup Interval commands and how to close a design and exit SmartRoute Opening a design You open Layout Plus MAX files in SmartRoute using the Open command To open a design 1 From the File menu choose Open The Open Design File dialog box displays 2 Locate and select a MAX design file 3 Choose the OK button Z Tip The files that you have opened most recently are listed at the bottom of the File menu You can select files from this list to open them This is the fastest way to open designs that you have worked on recently OrCAD Layout SmartRoute User s Guide 19 Chapter 4 Opening and saving designs Saving a design You save SmartRoute designs using the Save As command You can also use the Backup command to automatically save designs To save a design 1 From the File menu choose Save As The Save As dialog box displays 2 To save a board under a new name enter the name of the file locate the target directory and choose the OK button Or To save the board under the same name just choose the OK button SmartRoute asks you if you want to replace the existing file Choose the Yes button h3 Note There is no Save command in SmartRoute only a Save As command However you can use the Backup command to save a file without specifying a file name See Using backup in this chapter for
74. t Plus such as routing weight and track width Parameters Confirm and change if desired various parameters used by the autorouter such as number of layers direction of tracks on layers pad sizes and more Routing passes Select the routing passes that you want the autorouter to perform during the autorouting process OrCAD recommends that you use the default passes set by SmartRoute Note In almost all cases OrCAD recommends that you use the default values for net properties parameters and routing passes in SmartRoute OrCAD Layout SmartRoute User s Guide 23 Chapter 5 Setting up the board for routing Setting net properties Summary All nets in the database are routed except for VCC and GND which are fanned out in the instance of SMD components or edge fingers contained in the net The remaining nets through hole parts do not need to be fanned out because through hole parts connect to the plane The first step in setting up the board for routing is to check the net properties that SmartRoute received from Layout Plus You can do this in the Net Properties dialog box The dialog box is organized like a spreadsheet The names of all the nets in the design are listed on the left side A net name can be brought into view using either the vertical scroll bar or by entering the net name in the Find Net text box at the bottom of the dialog box As you spell the name of the net it is moved to the top of the spreadsh
75. t most nearly match each layer direction and routes the tracks in the selected direction on that layer The figure below shows two layers of a six layer board with layers routed at 45 up and 45 down 7 RA KL 45 up left 45 down right The basic movement uses long 45 diagonal segments with incremental orthogonal steps that align the track s direction with the selected layer direction 4 OrCAD Layout SmartRoute User s Guide Chapter 1 About SmartRoute Routing time power and guality Routing t me Routing power Routing guality This section discusses routing time power and guality in autorouting Routing time historically has been one of the prime criteria for evaluating autorouters But the rapid evolution of both software and high performance hardware has de emphasized the importance of routing time For example when teamed with powerful PCs a good autorouter should route nearly all six to eight layer boards with 4 000 5 000 connections in about 5 to 15 hours Routing power or the ability to route close to 100 of the connections has always been extremely important in autorouting And it is even more important today Designers know that if an autorouter routes only 95 to 96 of the connections the time required to interactively complete the 4 to 5 of unrouted connections is as great as the time it took to autoroute the first 95 If an autorouter achieves only 90 to 93 many design
76. ter the reference designator for example U9 To find a pad enter the reference designator and pad number for example U9 1 To find a location enter its X and Y coordinates for example 4982 5015 3 Choose the Find button To highlight a net 1 From the Tools menu choose Highlight Net The Highlight Net dialog box displays 2 Select the net that you want to highlight 3 Choose the Highlight button All connections of the selected net are displayed in the highlight color Note Highlighting a net is not persistent after a pan or zoom and changing a highlight value for any net in SmartRoute causes any previous highlights to be turned off for all other nets OrCAD Layout SmartRoute User s Guide 17 Chapter 3 The SmartRoute work environment To turn off a ne s highlight 1 From the Tools menu choose Highlight Net The Highlight Net dialog box displays 2 Select the net for which you want to turn off the highlight 3 Choose the End Highlight button To identify a net or pin 1 From the Tools menu choose Identify Net or Identify Pin The pointer changes to a vertical arrow 2 Select the desired net or pin For a net the connection length and net name are displayed in the status bar For a pin the pin name is displayed in the status bar amp Tip On large boards you may need to zoom in to select a net or pin to identify 18 OrCAD Layout SmartRoute User s Guide Chapter 4 Opening and saving de
77. the Density Graph command There are four commands in SmartRoute that you can use to change the view of the board displayed on the screen Zoom In Zoom Out Zoom Center and Zoom All Fit The Zoom In command magnifies a selected area of the board The Zoom Out command increases the board area displayed The Zoom Center command centers the selected area in the display The Zoom All Fit command displays the entire board in the display To magnify an area of the board 1 From the View menu choose Zoom In The pointer becomes a Z 2 Position the pointer at the upper left corner of the area that you want to magnify and while pressing the left mouse button drag the pointer to the opposite corner of the area Release the left mouse button The area is magnified 4 Press the ESC key to exit zoom mode Note There may be a delay when you choose the Zoom In command especially if you are autorouting a very dense board and the autorouter is currently routing a long connection In this case the command will be performed when the current connection is completed To view more of the board 1 From the View menu choose Zoom Out The pointer changes to a Z 2 Place the pointer at the center of the area you want to view and click the left mouse button 3 Press the ESC key to exit zoom mode 14 OrCAD Layout SmartRoute User s Guide Chapter 3 The SmartRoute work environment To center an area of the board in the dis
78. ting 5 tips for routing 61 new user 3 Tool menu tracks deleting 48 51 spacing 35 unrouting 51 width 26 30 troubleshooting design preparation checklist 53 routing 55 56 two layer boards routing 41 U Undo 45 units 29 Units parameter 29 30 Unroute Board command 57 Unroute Conflicts command 5 Unroute Connection command 51 Unroute Net command 57 Unroute Segment command 5 unrouted connections 56 57 unrouting tracks 5 user hints 3 V vertical routing 28 Via Type parameter 29 Via Width parameter 30 vias 49 minimization 6 no via zones 9 square 9 types 29 width 30 view board 4 View menu W X widths nets 26 pads 30 tracks 26 30 vias 30 Y vellow cireles 34 Z Zoom All Fit command 4 Zoom Center command 4 Zoom In command 4 Zoom Out command 74 OrCAD Layout SmartRoute User s Guide 69
79. u have opened the board file set up the net properties so that the signal connections will be routed and the power and ground connections will be reserved for planes The process below shows you how To set the net properties for an eight layer board 1 From the File menu choose Open The Open Design File dialog box displays 2 Go to the LAYOUT SAMPLES DEMOSR directory select BOARD3 MAX and choose the OK button 3 From the Options menu choose Net Properties The Net Properties dialog box displays 4 The plane nets for BOARD3 MAX are GND GND1 VDD and VDDI Find each plane net by typing its name into the Find Net text box at the bottom of the dialog box and set its Route Action option to Fanout Plane The Route Action option for the remaining nets signals should be set to Default 5 Choose the OK button 42 OrCAD Layout SmartRoute User s Guide Chapter 6 Autorouting and batch routing Setting up the layers SmartRoute provides you with two different approaches for setting up the direction in which routing is biased on each layer Orthogonal routing If routing speed is of primary importance select a direction by layer using either horizontal or vertical on all routing layers For example for four routing layers use horizontal vertical horizontal vertical or vertical horizontal vertical horizontal The primary direction by layer will be either horizontal or vertical but the router will use both diagonal and hor
80. uld expect from Layout Plus The design parameter options are described below Units From the drop down list select the desired data structure units for autorouting OrCAD recommends that you use the same unit structure that you used in Layout Plus Via Type From the drop down list select the type of vias that you want to use on your board OrCAD Layout SmartRoute User s Guide 29 Chapter 5 Setting up the board for routing Channel In SmartRoute the channel size that displays is automatically calculated by SmartRoute for your board To calculate this value SmartRoute adds the most frequently used track width on the board and the most common track to track clearance on the board SmartRoute then selects the channel value that is closest to that sum equal to or greater than it does not round down from the standard list of SmartRoute channel sizes listed in the SROUTE INI file This value reflects the optimum routing channel size for your board h3 Note Channel size may not be exactly the same as the system grid specified in Layout Plus channel size is calculated independently by SmartRoute using the primary track width and clearance parameter values in Layout Plus For example if you are routing a board with 12 mils tracks and 13 mils clearance SmartRoute sets the routing channel to 25 mils OrCAD strongly recommends that you use the default channel size calculated by SmartRoute When you return to Layout Plus the system grid
81. uring routing To pause the autorouter b From the Auto menu choose Pause AutoRouter SmartRoute temporarily suspends the autorouting seguence Note To restart the autorouter choose Restart AutoRouter from the Auto menu SmartRoute restarts the routing process from the point at which it paused To stop the autorouter o From the Auto menu choose Stop AutoRouter SmartRoute ends the autorouting sequence Note To restart the routing sequence choose the autoroute command of your choice from the Auto menu SmartRoute starts again at the first enabled routing pass Z Tip During autorouting SmartRoute displays an hourglass Even when this hourglass is displayed you can still access menu commands and pop up menu commands OrCAD Layout SmartRoute User s Guide 39 Chapter 6 Autorouting and batch routing Batch routing Batch commands are used to establish a list of different boards to be autorouted without operator intervention For example using batch routing you can route multiple boards overnight Batch routing consists of two steps Selecting files to add to the queue for batch routing Starting the batch route operation When the batch sequence is complete SmartRoute produces and displays the report SROUTE LOG that provides the details from the batch routing process If the router fails on any design in the sequence it skips on to the next board and displays the error in SROUTE LOG Tip If you only want the output
82. value will reflect the channel size selected by SmartRoute If you have different grid requirements you must change the system grid in Layout Plus h3 Note Note that if you change the Primary Track value or spacing rules channel size is recalculated after you choose the OK button in the Parameters dialog box SmartRoute is a gridless router It will try to place tracks on the channel specified but on dense boards this may not be possible Therefore changing the channel value for a dense board may have little effect on routing in SmartRoute Primary Pad The Primary Pad option displays the diameter width of the most commonly used pad on the board If there are no through hole pads the Primary Pad option displays the width of the largest SMD pad For instance on a board with 1000 pads from 50 components of various sizes there could be 20 different pad sizes and shapes The most common pad shape and size is displayed for the Primary Pad option Via Width The via width is the same as the first via defined in Layout Plus SmartRoute however will choose the best via size for a given situation when routing Primary Track The primary track width is the routing width of the majority of the nets as defined in Layout Plus If there are multiple track widths on a board for example all signal widths are 12 mils and all power and ground widths are 50 mils the primary track width would be 12 mils if there are a greater number of signal conne
83. y persist after all the previous passes are completed The ripup routing pass is then used to unroute the routed tracks associated with the contentions and reroute them eliminating the problem The number of contentions displays in the status bar interactively as routing progresses For more information about contentions see Contention in this chapter The term contention is a relatively new term in autorouting vocabulary All the routing passes in SmartRoute are based on contention routing That is it is permissible for the autorouter to place a track or via so that it creates a spacing violation contention with other tracks vias and pads Some examples of routing contention include A track segment crossing a track segment of a different net A track segment being placed on top of a track segment of another net A track segment that violates space requirements with an existing via or pad A via that violates space requirements with another via pad or track segment When a contention is created a small yellow circle approximately 0 1 in diameter hollow is created at the point of contention It remains until the contention is cleared Subsequent routing passes attempt to remove the contention by either pushing or rerouting the track that caused the contention or by pushing or rerouting the existing track If there is not enough room to push or reroute a track to eliminate the contention the contention remains and must be fixed by

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