Extender488 User`s Manual
Contents
1. the smart approach to instrumentation TM Measurement Computing 10 Commerce Way Norton MA 02766 508 946 5100 Fax 508 946 9500 info mccdag com www mccdag com Extender 488 User s Manual p n Extender488 901 1996 1997 by Measurement Computing Corp Part No Extender488 901 Printed in the United States of America Warranty Information Contact Measurement Computing by phone fax or e mail in regard to warranty related issues Phone 508 946 5100 fax 508 946 9500 e mail info mccdaq com Limitation of Liability Measurement Computing cannot be held liable for any damages resulting from the use or misuse of this product Copyright Trademark and Licensing Notice All Measurement Computing documentation software and hardware are copyright with all rights reserved No part of this product may be copied reproduced or transmitted by any mechanical photographic electronic or other method without Measurement Computing s prior written consent IOtech product names are trademarked other product names as applicable are trademarks of their respective holders All supplied IOtech software including miscellaneous support files drivers and sample programs may only be used on one installation You may make archival backup copies CE Notice Many Measurement Computing products carry the CE marker indicating they comply with the safety and emissions standards of the European Community When applicable these2. 3 7 8 Selected Device Clear SDC This causes a single device to be initialized to a pre defined or power up state 04 3 7 9 Serial Poll Disable SPD The SPD command disables all devices from sending their Serial Poll status byte 19 3 7 10 Serial Poll Enable SPE A device which is Addressed to Talk will output its Serial Poll status byte after SPE is sent and ATN is unasserted 18 3 7 11 Group Execute Trigger GET This command usually signals a group of devices to begin executing a triggered action This allows actions of different devices to begin simultaneously 08 3 7 12 Take Control TCT This command passes bus control responsibilities from the current Controller to another device which has the ability to control 09 3 7 13 Secondary Command Group SCG These are any one of the 32 possible commands Oto 31 in this group They must immediately follow a talk or listen address 60 to 7F 3 9 Section 3 IEEE 488 Primer 3 7 14 Parallel Poll Confisure PPC This configures devices capable of performing a Parallel Poll as to which data bit they are to assert in response to a Parallel Poll 05 3 7 15 Parallel Poll Unconfigure PPU This disables all devices from responding to a Parallel Poll 15 3 8 MORE ON SERVICE REQUESTS Most of the commands covered both uniline and multiline are the responsibility of the Active Controller to send and the bus devices to recognize Most of these happen routin
3. Section 1 4 Extender488 F SPECIFICATIONS IEEE 488 1978 Implementation Connector Fiber Optic Interface Wavelength Connectors Required Cable Max Cable Length General Data Rates Indicators Power Dimensions Weight Environment Controls Introduction Proprietary transparent control and data transfers Standard IEEE 488 connector with metric studs 820 nanometers typical SMA 905 series female Duplex 100um 140um clad fiber optic 200MHz km bandwidth 6 db km max attenuation 1000 meters 3400 bytes per second typical LEDs for IEEE Talk Listen SRQ Error and Power 105 125V or 210 250V 50 60 Hz 10 VA Max 188mm deep x 140mm wide x 68mm high 7 39 x 5 5 x 2 68 1 55 kg 3 6 lbs 0 50 C 0 to 70 to 35 C Linearly derate 3 R H C from 35 to 50 C Power Switch external Specifications subject to change without notice 1 4 Section 1 5 ABBREVIATIONS The following IEEE 488 abbreviations are used throughout this manual addr n ATN IEEE bus address n Attention line Controller Active Controller Carriage Return Data String Device Clear Group Execute Trigger Go To Local Listener Active Listen Address Group Line Feed Local Lock Out My Listen Address My Talk Address Peripheral Parallel Poll Configure Parallel Poll Unconfigure System Controller Selected Device Clear Serial Poll Disable Serial Poll Enable Service Request Talker Activ
4. bus Both local and remote extenders are identical At power up each extender monitors the Attention ATN and Remote Enable REN lines The Error LED on each extender will blink indicating that ATN or REN has not yet been detected and that communication with the other extender has not yet been established The first extender to detect either of these lines asserted declares itself the LOCAL extender and commands the other extender to declare itself the REMOTE extender The Error LEDs will now stop blinking From this moment on the LOCAL extender will monitor all local bus activity and transmit this activity to the REMOTE extender All activity detected by the REMOTE extender is also communicated back to the LOCAL extender 2 2 1 Extender488 Serial Baud Rate Selection The Extender488 is shipped with the serial baud rate set to 115 2K baud For most applications this is the most efficient operating rate However if the extenders are to be located at extreme distances from each other baud rates other than 115 2K can be selected Selectable baud rates include 115 2K 19 2K 9600 4800 2400 1200 600 300 Both extenders must be set to the same baud rate for proper operation To modify the baud rate follow this simple procedure Disconnect the power supply from the AC line and from the interface Disconnect any IEEE or serial cables prior to disassembly 2 2 Section 2 Getting Started WARNING Never open the Extender488 case while it is c
5. products have a Declaration of Conformity stating which specifications and operating conditions apply You can view the Declarations of Conformity at www mccdaqg com legal aspx CE Information page Warnings Cautions Notes and Tips A N 4 A amp Refer all service to qualified personnel This caution symbol warns of possible personal injury or equipment damage under noted conditions Follow all safety standards of professional practice and the recommendations in this manual Using this equipment in ways other than described in this manual can present serious safety hazards or cause equipment damage This warning symbol is used in this manual or on the equipment to warn of possible injury or death from electrical shock under noted conditions This ESD caution symbol urges proper handling of equipment or components sensitive to damage from electrostatic discharge Proper handling guidelines include the use of grounded anti static mats and wrist straps ESD protective bags and cartons and related procedures This symbol indicates the message is important but is not of a Warning or Caution category These notes can be of great benefit to the user and should be read In this manual the book symbol always precedes the words Reference Note This type of note identifies the location of additional information that may prove helpful References may be made to other chapters or other documentation T
6. t recent Parallel Poll information to the controller on the local bus This data should be discarded by the controller because it is not current After receiving a Parallel Poll the local exten der commands the remote extender to perform a Parallel Poll and returns the remote Parallel Poll data byte to the local extender The bus controller should now perform another Parallel Poll and use this data as the valid Parallel Poll byte The following table describes the minimum times the controller should wait between consecutive Parallel Polls in order to assure valid data on the second poll Extender488 Parallel Poll Response Times Baud Rate Delay typ 115200 1msec 19200 3 msec 9600 8 msec 4800 13 msec 2400 24 msec 1200 48 msec 600 92 msec 300 200 msec The minimum time the controller should wait with the Extender488 F between consecutive Parallel Polls is 1 millisecond 2 9 Section 3 IEEE 488 Primer IEEE 488 Primer 3 1 HISTORY The IEEE 488 bus is an instrumentation communication bus adopted by the Institute of Electrical and Electronic Engineers in 1975 and revised in 1978 The Extender488 and the Extender488 F conform to this most recent revision designated IEEE 488 1978 Prior to the adoption ofthis standard most instrumentation manufacturers offered their own versions of computer interfaces This placed the burden of system hardware design on the end user If his application required the products of several
7. to blink after the power on sequence this indicates one of two possible conditions either the system controller has not yet asserted the Attention line or communication with the mating extender has not yet been established Be sure both extenders are powered on the cabling has been installed and the controller has asserted Attention before assuming there is a problem Once all IEEE devices have been connected and powered on the Extender488 will allo w the system controller to co mmand up to 13 IEEE devices on its local b us in addition to itself and t he local extender and up to 14 IEEE devices on the remote bus in addition to the remote extender The extenders have no address of their own and therefore will operate completely transparent to the system with the exception of parallel poll Be careful not to have two IEEE devices with the same address connected to either remote or local buses Failure to do so will result in the bus locking up when one of the devices is accessed 2 8 Section 2 Getting Started 2 5 PARALLEL POLL RESPONSE TIMES The Parallel Poll function is the only extended bus transaction which is not completely transparent to your system This is because the speed at which data is transferred serially is slower than the IEEE specification for Parallel Poll response Consequently it is n ecessary for the controller to perform two Parallel Polls When the local extender detects the parallel poll it outp uts the mos
8. 7 6 3 7 7 3 7 8 3 7 9 3 7 10 3 7 11 3 7 12 3 7 13 3 7 14 3 7 15 3 8 3 8 1 3 8 2 Section 4 Appendix A Table of Contents IEEE 488 Primer Unlisten UNL Talk Address Group TAG Untalk UNT Local Lockout LLO Device Clear DCL Selected Device Clear SDC Serial Poll Disable SPD Serial Poll Enable SPE Group Execute Trigger GET Take Control TCT Secondary Command Group SCG Parallel Poll Configure PPC Parallel Poll Unconfigure PPU More On Service Requests Serial Poll Parallel Poll SERVICE INFORMATION Factory Service Theory of Operation Extender488 Component Layout Extender488 F Fiber Optic I O Layout Replaceable Parts List IEEE Command and Address Messages Section Introduction INTRODUCTION 1 1 DESCRIPTION The Extender488s enable IEEE 488 devices to be co ntrolled up to 4 000 feet from the h ost computer This overcomes the limit imposed by the IEEE 488 specification of 6 feet between any two devices to a maximum of 60 feet total chained length In addition the Extender488s allows up to 30 devices to be on the bus versus the 15 device limit imposed by the IEEE standard Two extenders are required to perform bus extension The bus connecting the host computer or controller is the local bus The bus to which control is extended is the remote bus One of the Extender488s is required on each bus to accomplish IEEE bus extension Communication between extenders is accompli
9. COMMANDS octal 25 PPU Message Mnemonic NAK ASCII ISO character hex 15 21 decimal ASCII 7 bit Code Chart KEY A l
10. Cu VIO eum 0102 cC lt v 4 2 Section 4 Service Information 4 4 Extender488 F FIBER OPTIC I O BOARD COMPONENT LAYOUT 5 4 3 Section 4 4 5 Extender488 and Extender488 F PARTS LIST Designation C101 C102 C103 C104 C105 C106 C107 C108 C110 C111 C112 C113 C115 C116 C117 C118 C123 C124 C201 C202 C203 D101 D102 D103 D104 D105 D106 J101 11025 J103 J104 J201 Part Numbers 4 4 Description 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v 0 luF Ceramic 25v 15pF Ceramic 25v 15pF Ceramic 25v luF Ceramic 25v 10uF Electrolytic 25v 10uF Electrolytic 25v 0 1uF Ceramic 25v 0 1uF Ceramic 25v Small Signal Diode Red PC Mount Red PC Mount Red PC Mount Red PC Mount Red PC Mount IEEE 488 Connector PC Mount Male DB 9 9 Volt Power Jack 13 x 2 0 1 Header Cable Assembly Service Information Section 4 Designation U101 U102 U102 U103 U104 U105 U106 U107 U108 U110 U111 U112 U113 U115 U116 R101 R102 R103 R104 R107 R201 R202 S101 S102 Y101 Part Numbers IC 1 Extender488 600 Extender488 F 600 IC 41 IC 23 IC 16 IC 3 IC 4 IC 5 Macro488 601 IC 38 IC 36 IC 33 IC 51 Extender488 601 R 1 68K RN 4 4 7K R
11. From this moment on the LOCAL extender will monitor all local bus activity and transmit this activity to the REMOTE extender All activity detected by the REMOTE extender is also communicated back to the LOCAL extender WARNING There are no user serviceable parts or us er selectable parameters inside the Extender488 F case Refer all servicing to qualified repair personnel Refer to Section 4 for additional information 2 3 1 Extender488 F Fiber Optic Connections The Extender488 F requires duplex fiber optic cabling Most cable manufacturers mark the two connectors at each end ofthe duplex cable with a T and an R to distinguish which to connect to the transmitter T and which to c onnect to the receiver R Connect the fiber optic cables as shown below The Transmitter of 1 is connected to the receiver of 2 and visa verse 2 5 Section 2 Getting Started Extender488 F Extender488 F There are several recommended precautions you should take to ensure years of trouble free operation 1 Treat the fiber optic transmitter receiver and cabling ends as you would treat an expensive camera lens Good system performance requires clean port optics and cable ferrules to avoid obstructing the optical path Clean compressed air iso ften all that s needed to remove dirt particles from the optic transmitters and receivers Standard lens cleaning tissues or cotton swabs soaked with methanol or Freon also work well for cleanin
12. N 1 10K RN 2 470 R 1 100 R 1 47 1 1 SW 8 SW 6 4 CR 4 Used on Extender488 only Used on Extender488 F only 4 5 Service Information Description MC68B09P Microprocessor Programmed EPROM 2764 Programmed EPROM 2764 8k x 8 CMOS SRAM 65B22 Versitile Interface Adapter R6551AP UART TMS9914ANL IEEE Controller SN75160BN IEEE Driver SN75162BN IEEE Driver Programmed 16L8A PAL 26LS30 RS 423 Driver 26LS33 RS 422 Receiver 74LS04 Hex Inverter 74LS74 Dual D Flip Flop Programmed 16L8A PAL 68K 1 4w carbon 4 7K1 x 7 SIP 10Kr x 9 SIP 47015 x 5 SIP 100 1 4w carbon 4715 1 4w carbon 1K 1 4w carbon DPST Rocker power switch 4 Pole DIP 7 3728 MHz Crystal Appendix A 87 B655 BITS 2 NUMBERS CONTROL SYMBOLS UPPER CASE LOWER 12 60 100 120 sP 0 9 1 Character Codes And IEEE Multiline Messages 1 i co 2 105 6 J Q6 TA A 153 173 101 k 6B 187 7B 123 154 174 110 1 i 8216 108 7 124 35 155 175 1101 CR Gs M m D 13j1D 23120 45150 61140 71150 95160 109 70 125 16 56 56 76 116 136 156 176 1110 50 RS E gt N A n Md E 1411 30 2 46 3E 62 4E 78 5 94 6 110 7E 126 17 37 57 77 117 137 157 177 1111 SI US I o e o N52 1511F 2 47 3F 53 4F BISF 95 6 1117 127 ADDRESSED UNIVERSAL LISTEN TALK SECCNDARY ACDRESSES COMMANDS COMMANDS ADDRESSES ADDRESSES OR
13. different manufacturers then he might need to design several different hardware and software interfaces The popularity of the IEEE 488 interface sometimes called the General Purpose Interface Bus or GPIB is due to thet otal specification of the electrical and mechanical interface as well as the data transfer and control protocols The use of the IEEE 488 standard has moved the responsibility of the user from design of the interface to design of the high level software that is specific to the measurement application 3 2 GENERAL STRUCTURE The main purpose of the GPIB is to transfer information between two or more devices A device can either be an instrument or a computer Before any information transfer can take place itis first necessary to specify which will do the talking send data and which devices will be allowed to listen receive data The decision of who will talk and who will listen usually falls on the System Controller which is at power on the Active Controller The System Controller is similar to a committee chairman On a well r un committee only one person may speak at a time and the chairman is responsible for recognizing members and allowing them to have their say On the bus the device which is recognized to speak is the Active Talker There can only be one Talker at a time if the information transferred is to be clearly understood by all The act of giving the floor to that de vice is called Addressing to Talk If the comm
14. e Talker Address Take Control Terminator Unlisten Untalk Unasserted 1 5 Introduction Section 2 Getting Started GETTING STARTED 2 1 INSPECTION The Extender488s are carefully inspected both mechanically and electrically prior to shipment When you receive the interface carefully unpack all items from the shipping carton and check for any obvious signs of physical damage which may have occurred during shipment Immediately report any damage found to the shipping agent Remember to retain all shipping materials in the event that shipment back to the factory becomes necessary Every 488 is shipped with the following e Extender488 IEEE bus extender interface e TR 2 or TR 2E Power Supply TR 4 115V TR 4E 220V 114 0920 Instruction Manual Note accessories ordered may be packaged and shipped separately WARNING The Extender488 requires a regulated external powers upply with a maximum output of 5 25 volts Using voltages above this level will result in damage to the interface Use only power supplies provided by Measurement Computing 2 1 Section 2 Getting Started 2 2 Extender488 CONFIGURATION The following describes the configuration necessary for the RS 422 Extender488s If you are using the fiber optic extenders refer to Section 2 3 Two Extender488s are required to accomplish bus extension with one c onnected directly to the LOCAL IEEE bus and the other connected to the REMOTE IEEE
15. e the other IEEE 488 lines are active low 3 5 1 Data Valid DAV The DAV line is controlled by the Talker The Talker verifies that NDAC is asserted active low which indicates that all Listeners have accepted the previous data byte transferred The Talker then outputs data on the bus and waits until NRFD is unasserted high which indicates that all Addressed Listeners are ready to accept the information When NRFD and NDAC are in the proper state the Talker asserts DAV active low to indicate that the data on the bus is valid 3 5 2 Not Ready for Data NRFD This line is used by the Listeners to inform the Talker when they are ready to accept new data The Talker must wait for each Listener to unassert this line high which they will do at their own rate when they are ready for more data This assures that all devices that are to accept the information are ready to receive it 3 5 3 Not Data Accepted NDAC The NDAC line is also controlled by the Listeners This line indicates to the Talker that each device addressed to listen has accepted the information Each device releases NDAC high at its own rate but the NDAC will not go high until the slowest Listener has accepted the data byte 3 6 Section 3 IEEE 488 Primer 1st Data Byte 2nd Data Byte S composite Y IEEE Bus Handshaking 3 6 DATA LINES The GPIB provides eight data lines for a bit parallel byte serial data transfer T
16. e factory for RS 422 transmission medium which prescribes differential receivers for high noise immunity To insure signal integrity only use shielded cable for the serial port connections If you are not using a cable provided by the factory below is the appropriate connections for proper operation Transmit Data 1 2 Local Extender Remote Extender Signal Pin Pin Signal Receive Data 1 4 6 Transmit Data Receive Data 24 7 Transmit Data Ground shield 5 lt 5 Ground shield Transmit Data 6 1 Receive Data Receive Data 2 4 Section 2 Getting Started 2 3 Extender488 F CONFIGURATION The following describes the configuration necessary for the fiber optic Extender488 Fs If you are using the RS 422 extenders refer to Section 2 2 Two Extender488 Fs are required to accomplish bus extension with one connected directly to the LOCAL IEEE bus and the other connected to the REMOTE IEEE bus Both local and remote extenders are identical At power up each extender monitors the Attention ATN and Remote Enable REN lines The Error LED on each extender will blink indicating that ATN or REN has not yet been detected and that communication with the other extender has not yet been established The first extender to detect either of these lines asserted declares itself the LOCAL extender and commands the other extender to declare itself the REMOTE extender The Error LEDs will now stop blinking
17. ely by the interface and are totally transparent to the system programmer Other commands are used directly by the user to provide optimum system control Of the uniline commands SRQ is very important to the test system and the software designer has easy access to this line by most devices Service Request is the method by which a bus device can signal to the Controller that an event has occurred It is similar to an interrupt in a microprocessor based system Most intelligent bus peripherals have the ability to assert SRQ A DMM m ight assert it when its measurement is complete if its input is overloaded or for any of an assortment of reasons A power supply might SRQ if its output has current limited This is a powerful bus feature that removes the burden from the System Controller to periodically inquire Are you done yet Instead the Controller says Do what I told you to do and let me know when you re done or Tell me when something is wrong Since SRQ is a single line command there is no way for the Controller to determine which device requested the service without additional information This information is p rovided by the multiline commands for Serial Poll and Parallel Poll Section 3 IEEE 488 Primer 3 8 1 Serial Poll Suppose the Controller receives a service request For this example let s assume there are several devices which could assert SRQ The Controller issues an SPE Serial Poll enable command to each device sequential
18. g cable ferrules Take care to avoid splashing methanol or Freon on case parts When not in us e replace Extender488 F optical transmitter and receiver protection caps Also ensure cable ferrule protection caps are also replaced When pulling optic cable through conduits of walls NEVER use the connectors as a link to the pulling lead Make sure that the cable is loose in the conduit after installation If the cable is pulled tight on a corner transmission loss may be increased significantly When seating connectors in the transmitter and receiver some rotation of the connector may be necessary to achieve satisfactory transmission 2 6 Section 2 Getting Started 2 4 OPERATION After configuring the Extender488s attaching the serial port or fiber optic cabling plug the power supply connector into the rear jack on the interface CAUTION Never install the power s upply into the interface while it is connected to AC line power Failure to observe this caution may result in damage to the Extender488 Only a supply with regulated 5 volt output should be used WARNING The power supply provided with the interface is int ended for INDOOR USE ONLY Failure to observe this warning could res ult in equi pment failure personal injury or death After installing the power s upply connector into the interface plug the power supply into the AC line power Place the rear panel power switch in the ON 1 position All front panel indicators s
19. hese eight data lines use the convention of DIO1 through DIOS instead of the binary designation of D0 to D7 The data lines are bidirectional and are active low 3 7 MULTILINE COMMANDS Multiline bus commands are sent by the Active Controller over the data bus with ATN asserted These commands include addressing commands for talk listen Untalk and Unlisten 3 7 1 Go To Local GTL This command allows the selected devices to be manually controlled 01 Section 3 IEEE 488 Primer 3 7 2 Listen Address Group LAG There are 31 0 to 30 listen addresses associated with this group The 3 most significant bits of the data bus are set to 001 while the 5 least significant bits are the address of the device being told to listen 3 7 3 Unlisten UNL This command tells all bus devices to Unlisten The same as Unaddressed to Listen 3F 3 7 4 Talk Address Group TAG There are 31 0 to 30 talk addresses associated with this group The 3 most significant bits of the data bus are set to 010 while the 5 least significant bits are the address of the device being told to talk 3 7 5 Untalk UNT This command tells bus devices to Untalk The same as Unaddressed to Talk 5F 3 7 6 Local Lockout LLO Issuing the LLO command prevents manual control of the instrument s functions 11 3 7 7 Device Clear DCL This command causes all bus devices to be initialized to a pre defined or power up state 14 3 8 Section 3 IEEE 488 Primer
20. hould light for approximately one second while the Extender488 performs internal ROM and R AM self check At the end of the power on sequence the ERROR LED should continue to blink indicating that communications with another extender has not been established Now repeat the above procedure with the second extender and observe the same results If any of the following LED conditions exist after power on a failure has occurred SYMPTOM FAILURE All lights remain on ROM test has failed All lights blink continually RAM test has failed No LEDs blink Power supply has failed 2 7 Section 2 Getting Started If any of the symptoms shown occur cycle the power switch on the Extender488 to be sure of the problem If the problem is unresolved refer to the Service Information section of this manual WARNINGThe Extender488 makes its earth ground connection through the I EEE interface cable Each extender must be connected to at least one IEEE device which is earth ground referred Failure to do s may allow the Extender488 to float to a voltage away from ground This co uld result in damage to the interface personal injury or death If proper operation is obtained turn off the Extender488 power switch and connect the other IEEE devices to each of the Extender488 s IEEE ports Connect the local extender to the remote extender via the serial or fiber optic cable Apply power to all devices in the system If the Extender488 ERROR LED continues
21. ips provide advice that may save time during a procedure or help to clarify an issue Tips may include additional reference Specifications and Calibration Specifications are subject to change without notice Significant changes will be addressed in an addendum or revision to the manual As applicable the hardware is calibrated to published specifications Periodic hardware calibration is not covered under the warranty and must be performed by qualified personnel as specified in this manual Improper calibration procedures may void the warranty Table of Contents Section 1 INTRODUCTION Description Available Accessories Extender488 Specifications Extender488 F Specifications Abbreviations Section2 GETTING STARTED 2 1 2 2 2 2 1 2 2 2 2 2 3 2 3 2 3 1 2 4 2 5 Section 3 Inspection Extender488 Configuration Extender488 Serial Baud Rate Selection Extender488 Serial Data Format Selection Extender488 Serial Port Cabling Extender488 F Configuration Extender488 Fiber Optic Connections Operation Parallel Poll Response Times IEEE 488 Primer History General Structure Send It To My Address Bus Management Lines Attention ATN Interface Clear IFC Remote Enable REN End Or Identify EOI Service Request SRQ Handshake Lines Data Valid DAV Not Ready For Data NRFD Not Data Accepted NDAC Data Lines Multiline Commands Go To Local GTL Listen Address Group LAG Section 3 3 7 3 3 7 4 3 7 5 3
22. ique address to avoid confusion In a similar fashion every building in town has a unique address to prevent one home from receiving another home s mail E xactly how each device s address is set is specific to the product s manufacturer Some are set by DIP switches in hardware others by software Consult the manufacturer s instructions to determine how to set the address Addresses are sent with universal multiline commands from the Active Controller These commands include My Listen Address MLA My Talk Address MTA Talk Address Group TAG and Listen Address Group LAG 3 4 BUS MANAGEMENT LINES Five hardware lines on the GPIB are used for bus management Signals on these lines are often referred to as uniline single line commands The signals are active low i e a low voltage represents logic 1 asserted and a high voltage represents a logic 0 unasserted 3 4 1 Attention ATN ATN is one of the most important lines for bus management If Attention is asserted then the information contained on the data lines is to be interpreted as a multiline command If it is not then that information is to be interpreted as data for the Active Listeners The Active Controller is the only bus device that has control of this line 3 4 Section 3 IEEE 488 Primer 3 4 2 Interface Clear IFC The IFC line is used only by the System Controller It is used to place all bus devices in a known state Although device configurations var
23. ittee chairman can not attend the meeting or if other matters require his attention he can appoint an acting chairman to take control of the proceedings For the GPIB this device becomes the Active Controller At a committee meeting everyone present usually listens This is not the case with the GPIB The Active Controller selects which devices will listen and commands all other devices to ignore what is being transmitted A device is instructed to listen by being Addressed to Listen This device is then referred to as an Active Listener Devices which are to ignore the data message are instructed to Unlisten The reason some devices are instructed to Unlisten is quite simple Suppose a college instructor is presenting the day s lesson Each s tudent is told to rais e their hand if the instructor has exceeded their 3 1 Section 3 IEEE 488 Primer ability to keep up while taking notes If a hand is raised the instructor stops his discussion to allow the slower students the time to catchu p In this way the instructor is certain that each and every student receives all the information he is trying to present Since there are a lot of students in the classroom this exchange of information can be very slow In fact the rate of information transfer is no faster than the rate at which the slowest note taker can keep up The instructor though may have a message for one particular student The instructor tells the rest of the class to ignore this mes
24. ly If any device responds with DIO7 asserted it indicates to the Controller that it was the device that asserted SRQ Often times the other bits will indicate why the device wanted service This Serial Polling sequence and any resulting action is under control of the software designer 3 8 2 Parallel Poll The Parallel Poll is another way the Controller can determine which device requested service It provides the who but not necessarily the why When bus devices are configured for Parallel Poll they are assigned one bit on the data bus for their response By using the Status bit the logic level of the response can be programmed to allow logical OR AND conditions on one data line by more than one device When SRQ is asserted the Controller under user s software conducts a Parallel Poll The Controller must then analyze the eight bits of data received to determine the source of the request Once the source is determined a Serial Poll might be used to determine the why Of the two polling types the Serial Poll is the most popular due to its ability to determine the who and why In addition most devices support Serial Poll only Section 4 Service Information SERVICE INFORMATION 4 1 Factory Service Measurement Computing maintains a factory service center in Norton Massachusetts If problems are encountered in using the Extender488 you should first telephone the factory Many problems can be resolved by discussing the problem with o
25. o Extender488 packages External power supply for Extender488 105 125v 50 60 Hz External power supply for Extender488 210 250v 50 Hz Refer to the Measurement Computing catalog for those accessories not listed here 1 2 Section 1 3 Extender488 SPECIFICATIONS IEEE 488 1978 Implementation Connector Serial Interface EIA RS 422A Connector Character Set Baud Rate Data Format Max Cable Length General Data Rates Indicators Power Dimensions Weight Environment Controls Proprietary transparent control and data transfers Standard IEEE 488 connector with metric studs Balanced voltage on TxD and RxD 9 pin Sub D female Proprietary asynchronous bit serial Selectable 300 600 1200 2400 4800 9600 19 200 and 115 200 Selectable 7 or 8 data bits 1 stop bit odd parity 1000 meters Specifications apply to data transfers after addressing has been established Baud Rate Data Rate bytes per second avg 300 13 600 26 1200 53 2400 105 4800 204 9600 385 19 2 691 115 2K 3400 LEDs for IEEE Talk Listen SRQ Error and Power 105 125V or 210 250V 50 60 Hz 10 VA Max 188mm deep x 140mm wide x 68mm high 7 39 x 5 5 x 1 35 kg 3 1 Ibs 0 50 C 0 to 70 to 35 C Linearly derate 3 R H C from 35 to 50 C Power Switch external Serial parameter switches internal Specifications subject to change without notice 1 3 Introduction 2 68
26. onnected tothe AC line Failure to observe this warning may result in equipment failure personal injury or death Remove the four screws located in each corner of the rear panel Hold the case firmly and pull the rear panel outward noting the slot location of the main circuit board Modify those parameters which are appropriate for your installation and reassemble the unit Slide the main circuit board into the previously noted slot and finish reassembly by tightening the four screws into the rear panel Extender488 Baud Rate Selection 011241 nha 5102 El 4 open 0 0 0 300 0 0 600 Default 115200 010 1200 1 O 2400 001 4800 0 1 9600 0 1 1 19200 1 1 115200 2 2 2 Extender488 Serial Data Format Selection The Extender488 is configurable for two data formats The first factory default format is 8 data bits 1 stop bit with odd parity The number of data bits transmitted can be set to 7 by setting 102 switch 4 to the closed position Even though the seven bit format is chosen binary data can still be transferred over the Extender488 s There will however be a slight degradation in data transfer speeds with this format 2 9 Section 2 Getting Started Extender488 Data Format Selection DOT Switch Side View 8data Bits 7data Bits Note Factory default is 8 data bits 2 2 3 Extender488 Serial Port Cabling The Extender488 is shipped from th
27. sage Unlisten and tells it to that one student at a rate which he can understand This information transfer can then happen much quicker because it need not wait for the slowest student The GPIB transfers information in asim ilar way This method of data transfer is called handshaking More on this later For data transfer on the IEEE 488 the Active Controller mustE a Unlisten all devices to protect against eavesdroppers b Designate who will talk by addressing a device to talk c Designate all the devices who are to listen by addressing those devices to listen d Indicate to all devices that the data transfer can take place 3 2 Section 3 IEEE 488 Bus Structure IEEE 488 Primer To Other Devices IA l Device 1 System Controller I H Able to Talk Listen and Control fal Data Bus i Device 2 DMM Able to Talk and Listen Data Byte Transfer Control Device 3 Printer Only Able to Listen General Interface Management Device 4 Frequency Counter Only Able to Talk DIO1 8 DAV NRFD NDAC IFC ATN SRQ REN EOI Figure 3 1 3 3 Section 3 IEEE 488 Primer 3 3 SEND IT TO MY ADDRESS In the previous discussion the terms Addressed to Talk and Addressed to Listen were u sed These terms require some clarification The IEEE 488 standard permits up to 15 devices to be configured within one system Each of these devices must have a un
28. shed with serial data transmission using RS 422 data drivers and receivers with the Extender488 This differential serial data format provides high noise immunity and long distance capability using low cost twisted pair wire The Extender488 F communicates serially over duplex fiber optic cables Fiber optic transmission provides high noise immunity low RFI emissions and long distance capability Operation of the Extender488s is completely transparent to the system The controller can access both local and remote devices in exactly the same manner with the exception of Parallel Poll 1 1 Section 1 2 AVAILABLE ACCESSORIES Introduction The following accessories are available from Measurement Computing for use with the Extender488s CA 7 1 CA 7 2 CA 7 3 CA 7 2 CA 18 X CA 24 X CN 20 CN 21 CN 22 CN 23 114 0920 Rack488 1 Rack488 2 TR 2 TR 2E 1 5 foot IEEE 488 cable 6 foot IEEE 488 cable 6 foot IEEE 488 cable shielded 6 foot IEEE 488 cable reverse entry Shielded serial cable with mating connectors for the Extender488 specify X in feet from 100 to 4000 100um 140um duplex fiber optic cable with mating connectors for the Extender488 F specify X in feet from 100 to 4000 Right angle IEEE 488 adapter IEEE 488 connector extender IEEE 488 multi tap bus strip 4 connectors in parallel IEEE 488 panel mount feed thru connector Additional Manual Rack mount kit one Extender488 package Rack mount kit tw
29. ur applications department If the problem cannot be solved by this method you will be instructed as to the proper return procedure 4 2 Theory of Operation At the heart oft he Extender488 is a 6809 microprocessor U101 supported by 8K bytes of firmware EPROM U102 2764 and 8K bytes of static RAM U103 6264 A counter U105 65C22 contained in the VIA is used to generate real time interrupts for the firmware operating system The front panel annunciators are driven by the VIA through an inverter driver U113 74LS04 Serial communication to the mating Extender488 is accomplished by a UART U105 thru the RS 422 receiver U112 and driver U111 For the Extender488 F it is accomplished by the UART and fiber optic transmitter U202 and receiver U203 The IEEE 488 bus is monitored by 9914A IEEE bus device 0106 Circuitry surrounding the 9914A U115 and U116 enables the device to monitor all bus activity and to initiate bus activity when required Decoding of the microprocessor address space is accomplished with a pr ogrammed PAL U110 16L8 Below is the memory space allocation Address Device Part Number Function 6000 7FFF U103 6264 Static RAM A000 A007 U106 9914A IEEE Controller A800 A803 U105 6551 UART B000 BOOF U104 65C22 VIA E000 FFFF U102 2764 Programmed EPROM 4 1 Service Information _ Section 4 4 3 Extender488 COMPONENT LAYOUT or Cars 601 60 Macro488 Extender 488 s CIO
30. y the IFC command usually places the devices in the Talk and Listen Idle states neither Active Talker nor Active Listener 3 4 3 Remote Enable REN When the System Controller sends the REN command bus devices will respond to remote operation Generally the REN command should be issued before any bus programming is attempted Only the System Controller has control of the Remote Enable line 3 4 4 End or Identify EOD The EOI line is used to signal the last byte of a multibyte data transfer The device that is sending the data asserts EOI during the transfer of the last data byte The EOI signal is not always necessary as the end of the data may be indicated by some special character such as carriage return The Active Controller also uses EOI to perform a Parallel Poll by simultaneously asserting EOI and ATN 3 4 5 Service Request SRQ When a device desires the immediate attention of the Active Controller it asserts SRQ It is then the Controller s responsibility to determine which device requested service This is accomplished with a Serial Poll or a Parallel Poll 3 5 Section 3 IEEE 488 Primer 3 5 HANDSHAKE LINES The GPIB uses three handshake lines in an I m ready Here s the data I ve got it sequence This handshake protocol assures reliable data transfer at the rate determined by the slowest Listener One line is controlled by the Talker while the other two are shared by all Active Listeners The handshake lines lik
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