Procidia Control Solutions Ethernet Peer-To-Peer
Contents
1. Siemens Industry Inc is not responsible for changes to product functionality after the publication of this document Customers are urged to consult with a Siemens Industry Inc sales representative to confirm the applicability of the information in this document to the product they purchased Siemens Industry Inc assumes no liability for errors or omissions in this document or for the application and use of information in this document The information herein is subject to change without notice Copyright 2012 Siemens Industry Inc 102. SIEMENS APPLICATION DATA AD353 113 Rev 2 April 2012 Procidia Control Solutions Ethernet Peer To Peer Communication Ethernet is a leading form of network communication that is often employed on industrial process networks Data is exchanged between network connected Ethernet enabled process controllers personal computers and field instruments to control and monitor a process This data can be shared throughout a company and by way of the Internet it can be made available to remote locations almost anywhere in the world Presented here is an overview of peer to peer communication on a private Ethernet network that includes Procidia controllers See Application Support on page 9 for a list of controllers There are private and public networks In this paper we are concerned with the private network A private network has access intentionally restricted to specific individuals usually within a company or within one specific area within a company Private networks can be linked for efficient exchange of data Open access characterizes a public network The Internet is an example of a public network where anyone with the requisite computer and software can log on In this paper we discuss what Ethernet is describe building a network and briefly introduce network addressing Next controller configuration and Ethernet function blocks are discussed Finally controller firmware and hardware requirements are list
3. and the router is a member of the gateway class A gateway is often able to connect two different types of networks together for example connecting an Ethernet network to an IBM SNA System Network Architecture network A public network such as the Internet can be connected to a private network through a gateway or a router For information about configuring a gateway or router refer to the manufacturer s installation manual IP Address This section introduces IP addressing Addressing is a complex topic particularly when several networks and sub networks are involved Your company s network administrator will supply host addresses masks subnet addresses and gateway addresses as needed Addressing is an inseparable part of network design Every host on a network needs a unique address In Figure 1 addresses 1 2 and 3 were used The Internet Protocol IP uses a 32 bit addressing structure An example of an IP address is 192 168 0 2 Notice that the complete address is written as four numbers in a dotted decimal notation i e the four decimal groups are connected together by three dots Each decimal number has a range of 0 to 255 AD353 113 A portion of the complete address represents the network address netid another portion the subnet address subnetid on a more complex network and a third portion the host address hostid However it is important to remember that all four decimal numbers provide t
4. T or OOBASE T P2P RATE Peer to Peer Communication Rate The Peer to Peer parameter specifies in seconds how often the controller issues a data request command AD353 113 AIE Function Block The AIE function block is used to request analog data from another controller on the network In a typical application a supervisory controller provides an external set point to a loop controller Thirty two 32 AIE blocks are available per controller Example In a steam powerhouse application the plant master controller regulates the main steam header pressure All boilers are connected to the main header and the header provides steam to the plant Each boiler controller relies on the plant master to dictate the percentage of full capacity at which it should be running This value is the plant fire rate demand FRD To transfer the plant FRD across an Ethernet network each boiler controller will contain an AIE function block in the boiler master loop See Figure 6 function block used It replaces the AIN with traditional field wiring The boiler controller will periodically issue a data request command to get the latest plant FRD Switch The plant master controller will have the compliment AOE block The purpose of the AOE block is to provide a memory location for the plant FRD value The plant master controller being a Modbus slave will respond with the value located in the specified Modbu
5. because when using the Graphical Configuration Utility the controller configuration is more thoroughly documented The CIE is available for completeness and it allows access to certain discrete statuses that are not available via function block outputs It may be of value for example to know if an alarm has been acknowledged or that a controller is in run mode station coil 00008 Application support User manuals for controllers and transmitters addresses of Siemens sales representatives and more application data sheets can be found at Wwww usa siemens com ia To reach the process controller page click Process Instrumentation and then Process Controllers and Recorders To select the type of assistance desired click Support in the right hand column See AD353 138 for a list of Application Data sheets The controller configurations discussed in this publication can be implemented with the Siemens ilconfig Graphical Configuration Utility Controller Firmware and Hardware Requirements The following Procidia controllers are Ethernet capable when the listed firmware and hardware items are installed Model 353R with e Design Level B Controller Carrier TGX 353RRCCB_ e ilpac Ethernet Communication Board e Firmware V2 40 or higher Procidia ilpac Internet Control System with e Design Level B Controller Carrier Model iPAC CC B4 e ilpac Ethernet Communication Board e Firmware V2 40 or higher Mo
6. controller address is provided One controller on a network can use this address A unique address will need to be assigned to each additional controller AD353 113 Ethernet Function Block The ETHERNET function block is used to assign the controller IP address and to set communication parameters The ETHERNET function block is located under Station Function Blocks IP ADRES IP Address Each controller requires a unique IP address Enter the address assigned by the network administrator Alternatively if this is a private network use an address from the blocks of reserved IP addresses listed earlier in this paper IP MASK Subnet Mask The subnet mask is the method used to identify messages that are addressed to members of a subnet More than one subnet can exist in the same network If the subnet address is 192 168 175 0 then use IP mask 255 255 255 0 If the subnet address is 192 168 175 128 then use IP mask 255 255 255 128 Your network administrator will provide the needed addresses and masks Figure 5 is an example of bit wise logic illustrates how the subnet ETH DPLX Ethernet Duplex mode The Ethernet Duplex mode parameter specifies how devices e g switches routers communicate with each other It is recommended to set ETH DPLX parameter to Automatic mode When the host registers with the switch or gateway it establishes the communication mode The Full Duplex and Half Duplex mode options are availa
7. Data IEEE and not the Dynamic Loop Integer Data It is possible to request IEEE formatted data from other hosts that support Modbus TCP IP protocol The default host Modbus address is 1 Important The AIE function block assumes that data is in IEEE format and request two registers of data Range When data is to be displayed in the controller or ilstation faceplate scaling information is important This information also affects the performance of the PID and other loop function blocks The standard procedure is to assign the MINSCALE MAXSCALE DPP and ENGUNITS parameters of an analog input block When the RANGE parameter is in Automatic mode scaling information comes from the AOE block in the source controller In Manual mode the scaling information specified in the AIE function block parameters is used In the Auto mode the advantage of this parameter is that any changes made to the scaling parameters of the source controller are applied to all other controllers in the network It is good engineering practice to configure all range pointers The default setting is Manual mode Important If requested data does not come from an AOE block set the RANGE parameter to Manual and set the MINSCALE MAXSCALE DPP and ENGUNITS parameters appropriately See the controller s User s Manual Note Since data is transferred in IEEE format the value is not altered AOE Function Block The AOE function block is used to map
8. analog data to the Modbus registers to make it available to the network i e the AIE block in another controller Thirty two 32 AOE blocks are available per controller The AOE block does not contain scaling information If the associated AIE block is requesting scaling information Range is Automatic mode then the AOE range pointer must be configured to an appropriate analog input or scalar function block Refer to the controller s User s Manual for additional information about this block DIE Function Block The DIE function block is used to request discrete data from a second controller on the network Thirty two 32 DIE function blocks are available per controller Each DIE function block supports 16 discrete points A separate DIE block is required for each controller from which data is requested Refer to the controller s User s Manual for additional information about this block Note In Procidia controllers discrete data is normally stored in the Modbus coils Since this command issues a read register command it cannot be used to request controller discrete data The CIE block issues the read coil data command IP ADRES IP Address The IP address of the source controller is required MB REG Modbus Register Embedded within the Modbus command is the starting register address and the number of consecutive registers to be read The function block assumes that the data is in bit format and requests one
9. ble in the event that other hosts on the network support only one mode Consult with the network administrator before making a selection other than that recommended here ETH Rate This Ethernet Rate parameter refers to more than the communication baud rate It refers to the network wiring specification and topology Most hosts can support both Ethernet 1OBASE T 10 mbps and 100BASE T 100 mbps Set the ETH RATE parameter to Automatic When the host registers with the switch or gateway it establishes the baud rate for each connection The 1OBASE T and 100BASE T options are available for unique network topologies Consult with the network administrator mask works before making a selection other than that recommended here e IP Address 11000000 10101000 10101111 00000010 192 168 175 2 e Subnet Mask 11111111 11111111 11111111 00000000 255 255 255 0 e AND bit logic e Subnet Address 11000000 10101000 10101111 00000000 192 168 175 0 Figure 5 Subnet Mask Example IP GATE Gateway IP Address If the local network is isolated by a gateway then the gateway IP address needs to be specified Typically it is assigned the first host address in the subnet e g 192 168 175 1 or 192 168 175 129 A gateway address must be assigned If a gateway is not present the gateway field should contain an unused address within the host subnet address range When using a switch each host to switch connection can be set for either 1 OBASE
10. del 353 Process Automation Controller Design Level B or Design Level A with e Mounting Case Option 4 with RJ 45 Ethernet connector Model 353_4 e Model 353 Ethernet Communication Board e Firmware V2 40 or higher Discontinued model AD353 113 References SAMS Teach Yourself Networking in 24 Hours Matt Hayden SAMS Publishing 2001 Networking with Microsoft TCP IP Drew Heywood New Riders Publishing Networking Complete Second Edition Sybex Inc 2001 Procidia ilpac User s Manual UMiPAC 1 Rev 4 or higher Model 353 Process Automation Controller User s Manual UM353 1 Rev 9 or higher Siemens Controller Configuration Training Class For information follow the navigation on the previous page and click Training or request information from Siemens Industry Inc Technical Training Center MS510 1201 Sumneytown Pike P O Box 900 Spring House PA 19477 0900 Procidia ilpac ilware ilconfig and 352Plus are trademarks of Siemens Industry Inc Other trademarks are the property of their respective owners All product designations may be trademarks or product names of Siemens Industry Inc or other supplier companies whose use by third parties for their own purposes could violate the rights of the owners Control circuits are provided only to assist customers in developing individual applications Before implementing any control circuit it should be thoroughly tested under all process conditions
11. ed The scope of this paper is limited to introductory material However the References section on the last page has a list of books and manuals that provide in depth information about the above topics plus network security wiring and troubleshooting Siemens offers training classes that include configuring a controller for Ethernet operation see the References section The final word though belongs to your company s network administrator He or she is a primary source of additional information about network security design IP addressing and other critical network issues Ethernet and Procidia Ethernet is simply an agreed upon set of rules that describes how devices will exchange messages These rules are published in IEEE specification 802 3 and they describe in detail the critical aspects of Ethernet communication including the format of the data packets and the physical interconnections cables and connectors The Ethernet form used by Procidia controllers is Modbus TCP IP Transmission Control Protocol Internet Protocol Messages are correctly addressed and routed by IP TCP insures that all packets of data are received correctly Simply stated Modbus TCP IP is Modbus communication encapsulated in an Ethernet TCP IP wrapper Before delving further into Ethernet some Modbus characteristics need to be mentioned Modbus is a common communications protocol supported by many instrument manufacturers Modbus communicati
12. ge If two hosts do send messages at the same time the messages collide and become unreadable Hub paDaas era Ethernet mR Enabled Field Device Pe Address 2 Model 353 Model 353 Control Room HMI Address 3 Address 1 Figure 1 Hub Based Ethernet Network Collision avoidance is built into Ethernet through the use of CSMA CD Carrier Sensing Multiple Access with Collision Detection When a host needs to send a message it first listens to the network to determine if another host is sending a message After a short period of network inactivity the host sends its message If another host attempts to send a message at the same instant both stop and wait a random length of time before attempting to re send their messages Since each host s wait time is random the previous communication collision is unlikely to be repeated However each collision and ensuing wait time reduces the volume of traffic that can flow on the network The design of the network can reduce the probability of collisions and significantly increase network traffic The controllers are Modbus slaves by design and respond to Modbus commands To enable the controllers to initiate Ethernet peer to peer communication Ethernet communication function blocks are included in firmware version 2 40 and higher There are three function blocks that initiate co
13. he complete address A brief example of the use of subnet addresses and subnet masks is provided later in this paper If the network is not connected to another network particularly the Internet almost any IP addresses can be assigned However the IANA Internet Assigned Numbers Authority has reserved three blocks of addresses for private networks These reserved address ranges should be used whether or not a connection to a public network is anticipated 192 168 0 0 192 168 255 255 or 172 16 0 0 172 31 255 255 or 10 0 0 0 10 255 255 255 through through through A default address is provided by a controller It can be used in many applications where the process control network is not connected to other networks When a Windows based PC is to be configured make the needed entries in the dialog box shown in Figure 4 Your network administrator can provide addresses subnet masks and other necessary information Peer to Peer Configuration To configure peer to peer communication between controllers build each controller s configuration as you normally would Wherever an external analog value or point is to be exchanged over Ethernet add an AIE or AOE function block to the configuration Note that more than one AJE block can request data from a single AOE block Make a list of each Ethernet analog block created and the loop where it is located for later connection Where an external discrete value or point is t
14. he design of the network Your company s network administrator will play a primary role by examining security issues assigning addresses and deciding other critical issues Process engineering will identify the equipment that is to be connected to the Ethernet network Company management may be interested in connecting a network that links the purchasing and accounting departments to the process control network If remote monitoring is required an intranet extranet or the Internet may also be connected Network reliability and security will be of immense concern to all involved Ethernet Network with a Hub In Figure 1 a hub is used to connect the controller field instrument and HMI The hub is simply a central point to which a number of hosts often as many as 8 12 can be electrically connected Every message sent by a host is sent to every other connected host but read by only the addressed host The hub distributes the message but since it is a passive device it cannot direct the message only to the addressed host As pointed out earlier a collision occurs when two hosts try to send a message at the same instant With only three hosts network performance is probably adequate However as additional hosts are connected to accommodate plant or process expansion network performance suffers Since only one host at a time can access the network and there are now more hosts network traffic increases the number of collisions i
15. mmunication AIE Analog Input for Ethernet communication DIE Digital Input for Ethernet and CIE Coil Input for Ethernet Each block issues a data request command The compliments to the above blocks are the AOE Analog Output for Ethernet and DOE Digital Output for Ethernet function blocks These blocks do not initiate communication They map data to the controller s Modbus registers memory locations where the data are stored Data in the Modbus registers are available to the network Note that controllers cannot initiate write commands This privilege belongs to an operator who can initiate actions through an HMI such as a Procidia ilstation Building a Network The manner in which hosts are connected together to create a network is referred to as the network topology This includes the cabling of the network connected hosts and the use of hubs switches routers and gateways to accommodate that cabling and create the desired network structure Figures 1 and 2 show simple networks Figure 3 shows two networks connected through a router These arrangements or topologies will be discussed in this section Each host connected to a network must have a unique identifier known as an address equivalent in purpose to your home address for Post Office mail delivery In Figure 1 the addresses are 1 2 and 3 A message can be sent for example from the HMI at address 1 to the controller at address 3 the field instrument at add
16. ncreases and performance degrades The use of a hub to interconnect hosts is generally not recommended The solution is to replace the hub with a switch also known as a switching hub Ethernet Network with a Switch A switch like a hub interconnects hosts However the switch directs traffic more effectively since it can read addresses and route a message directly to the addressed host In Figure 2 a message sent by host 1 to host 2 is not sent to hosts 3 and 4 Indeed at the same time hosts 1 and 2 are communicating hosts 3 and 4 can be communicating The switch isolates the simultaneous communications allowing an increase in network traffic while reducing message collisions Router or Gateway Connected Networks A router is used to connect together networks of the same type for example two Ethernet networks Figure 3 shows two routers with built in switches connecting a process area network to an office area network The office network includes the purchasing and accounting departments and a web server and gateway with a security firewall for access to the Internet A router can read an address and route a message to the proper network and to the addressed host In addition a router isolates the networks and can usually prevent a problem on one network from affecting other connected networks Network performance and reliability are significantly improved A gateway is a general term for devices that link two networks together
17. o be acquired over Ethernet add a DIE block Since the DIE block supports 16 points it is likely that several loops will need to connect to it Create a separate I O Discrete loop and place one DIE block for each zixl Microsoft TCP IP Properties 2 xi IP Address DNS WINS Address Routing An IP address can be automatically assigned to this network card by a DHCP server If your network does not have a DHCP server ask your network administrator for an address and then type it in the space below Adapter 1 3Com EtherLink XL NIC 3C900B TPC E Obtain an IP address from a DHCP server Specify an IP address IP Address 192 168 000 002 Subnet Mask 255 255 255 0 Default Gateway 192 168 000 001 Advanced 4 cov toh Figure 4 Sample Windows TCP IP Properties Dialog Box network connected controller from which data or status will be obtained Make a list of each Ethernet discrete input block created and the loop where it is located Where a discrete value is to be stored in the controller s Modbus registers add a DOE block to the configuration Note this register location for later connection When finished return to each configuration and tie the Ethernet I O blocks Next assign IP addresses to each controller The last step is to go through each AIE and DIE function block and set the source IP address and Modbus register location A default
18. on is based on one master device and one or more slave devices each slave having a unique identity or address Usually the master is a PC or PLC Slave devices can be controllers slave PLC s and field instruments Only the master can initiate communication and it can issue either a data request or a write data command The Modbus command contains the unique address of the slave to which the message is directed the command function code the starting register address and the number of registers affected Procidia controllers see page 9 are capable of Modbus TCP IP and HTTP over 10BaseT and 100BaseT AD353 113 The slave recognizes its address performs the command operation and sends a response The response is either the data requested or a reply that it received the write command The starting register address and the number of registers affected specifies the location and size of the data On a Modbus network the master must wait for the reply before issuing another request This architecture does not allow peer to peer communication between slave devices Unlike Modbus Ethernet communication supports peer to peer communication because it permits all devices known as hosts in Ethernet parlance to initiate communication In Figure 1 three hosts are connected together through a hub forming a network Any host can send a message through the hub to the other hosts However only one host at a time can send a messa
19. register of data A register is 16 bits For convenience the starting register for each DOE is listed in the User s Manual under the DIE function block section AD353 113 Important The DIE block assumes that data is in bit format and requests one register of data DOE Function Block The DOE function block is the compliment of the DIE This block maps the discrete outputs of other function blocks to the Modbus registers Thirty two 32 blocks are available per controller and 16 points can be configured per block Refer to the controller s User s Manual for additional information about this block CIE Function Block The CIE function block is used to request discrete coil data from another controller on the network Thirty two 32 CIE function blocks are available per controller Each CIE function block can obtain up to 16 consecutive coils There is no compliment block for the CIE Refer to the controller s User s Manual for additional information about this block Modbus coils are memory locations where discrete data is stored in bit format Coils are different than registers and can be visualized as a different sector in memory Coils have their own set of data request and write commands Controller discrete logic data is available as outputs of function blocks In peer to peer communication use DIE and DOE blocks where needed to transfer discrete data This method is recommended over using the CIE block
20. ress 2 will receive the message but ignore it since the message was not addressed to it This is point to point or peer to peer communication Broadcast communication allows a host to send a message to all other network connected devices AD353 113 Switch siemens 242345 siemens F aa 3 iz Ethernet S Enabled Field Device Address 2 Model 353 Model 353 A o MD 3 Model 353 Model 353 Control Room HMI 3 Address 4 Address 1 Address 3 Figure 2 Switch Based Ethernet Network F Internet PC in Purchasing PC in Accounting Web Server i y 2 To From Ly Gateway Switch Internet Router Note Router Switch combination may be two separate devices Office Area Network Process Area Network Router g Switch 8 Sasa TOES F F Ethernet oy E Enabled BRIS Field Device c en Model 353 Model 353 MELEE d Model 353 Model 353 Control Room HMI Figure 3 Ethernet Network with Router and Gateway AD353 113 Many people will participate in t
21. s registers IP ADRES Source IP Address The IP address of the source controller is required MB REG Modbus Register Embedded within the Modbus command is the starting register address and the number of consecutive registers to be read The function block assumes that the data is in IEEE floating point format and it requests two registers of data A register is 16 bits For convenience the starting register for each AOE is listed in the User s Manual under the AIE function block section MG00422a TC2053 Pl Model 353 semens 242345 TC2053 P Model 353 ms 242345 TC2053 P Model 353 Plant Master Boiler 1 Boiler 2 Steam Pressure Boiler Master Boiler Master AOE1 H AIE1 AIE1 1 O Discrete I O Discrete I O Discrete pier E DE2 E Jpoe1 4poe2 DIET DOE DIE1 DOEI Figure 6 Ethernet Peer To Peer Communication AD353 113 Data can be requested from registers other than AOE blocks For example the process set point and valve variables can be read directly from the ODC block Be sure to select the Modbus registers from the Dynamic Loop Floating Point
Download Pdf Manuals
Related Search