Rockwell Automation 1785 PLC-5 User Manual Page 1

UserManualPLC-5 BackupCommunicationModule(1785-BCM, 1785-BEM)Allen-Bradleyproduct icon

Chapter 11-1Backup Concepts for the PLC-5 SystemThis chapter describes concepts for using a backup system with yourprogrammable controller. In additi

Programming TechniquesChapter 77-3This manual provides two solutions to programming your PLC-5 backup systemto transfer data table values. These meth

Programming TechniquesChapter 77-4Program Operation in the Primary SystemIn the primary system’s program, COP instructions move data with a block IDof

Programming TechniquesChapter 77-5In addition, the secondary 1785-BCM module compares the segment lengthspecified in the secondary program’s BTW instr

Programming TechniquesChapter 77-6Method 2 — Transferring Data Multiple Blocks at a TimeIn the second method, transferring data multiple blocks at a t

Programming TechniquesChapter 77-7Program Operation in the Primary System The primary processor’s program executes the 3 BTW instructions to theprima

Programming TechniquesChapter 77-8Figure 7.3Program Flow for Transferring Data Multiple Blocks at a TimeBTR 1BTW 1MAIN PROGRAMDECIDE P

Programming TechniquesChapter 77-9Some instructions, when used with a PLC-5 backup system, may operateunpredictably when a switchover occurs if you fa

Programming TechniquesChapter 77-10The hardware timer of the primary processor is completely asynchronous to thehardware timer of the secondary proces

Programming TechniquesChapter 77-11As with the timer instruction, your program should transfer the counteraccumulated value from the primary to the se

Programming TechniquesChapter 77-12Block Transfer InstructionsIt is impossible to guarantee that both processors are executing a given BTW orBTR at th

Backup Concepts for the PLC-5 SystemChapter 11-2A PLC-5 system configured with 1785-BCM modules provides high speedbackup communication and switchover

Programming TechniquesChapter 77-13When developing a program for the PLC-5 backup system, you must alwaysconsider the following: non-synchronous I/O

Chapter 88-1Diagnosing FaultsThis chapter describes how to diagnose faults with your PLC-5 backupsystem using: status indicators on the front of the

= on= offDiagnosing FaultsChapter 88-2Primary (PRI) and Secondary (SEC) LED IndicatorsTable 8.B lists the possible states of the PRI and SEC LEDs and

= on= off= blinkingLEGEND:Diagnosing FaultsChapter 88-3Table 8.CBPLN, SER, and FLT LED IndicatorsIf this LED is: Description Recommended ActionBPLNSER

Diagnosing FaultsChapter 88-4In the 1785-BCM module, two bits of the status word serve to inform thePLC-5 processor of the state of the local and remo

Diagnosing FaultsChapter 88-5Figure 8.2System Status Word Error IndicationsRemote BCMmodule bitsLocal BCMmodule bits8910111213141501234567 If bit

Diagnosing FaultsChapter 88-6Diagnosing Faults with Bits of the Auxiliary Diagnostic/Status WordsBits of the two Auxiliary Diagnostics/Status Words pr

Diagnosing FaultsChapter 88-7Figure 8.4BCM and BEM Modules Configuration Status Word W2(Auxiliary Diagnostic/Status Word)171615141312111076543210Chann

Chapter 99-1SpecificationsThe following specifications are for a 1785-BCM series B module and a1785-BEM series A module.Compatible Processors PLC-5/15

AppendixAA-1Sample ProgramsThis appendix provides two sample programs to help you understand thefollowing programming methods described in Chapter 7:

Backup Concepts for the PLC-5 SystemChapter 11-4Figure 1.1PLC-5 Backup System Configuration Using 1785-BCM Module OnlyHSSL1771 –P4SPower Supply1785 –B

Sample ProgramsAppendix AA-2Table A.AData FilesThis information: Is in file:BTR and BTW control files and storage words N30BTR data files (this is whe

Sample ProgramsAppendix AA-3Program file 9 contains the secondary subroutine. This file: checks the block ID of the BTR moves the BTR data to the p

Sample ProgramsAppendix AA-4SAMPLE 1771–BCM 1ATATIME PROGRAM 28 August 1991 Page 1Program Listing Report PLC–5/2

Number of blocksto transferSample ProgramsAppendix AA-5Rung 2:2| |1=LOCAL IS || PROG

Sample ProgramsAppendix AA-6Rung 2:5THIS SUBROUTINE MONITORS THE BLOCK TRANSFER WRITES, READS, READ STATUS DATA ANDINCREMENTS COUNTERS ON ERRORS. PART

Sample ProgramsAppendix AA-7Rung 9:0THIS IS THE SECONDARY SUBROUTINE. THIS RUNG EXAMINES THE DATA FROM THE BCM,CHECKS THE BID, AND MOVES IT TO THE PRO

Sample ProgramsAppendix AA-8Rung 10:0OPTIONAL RUNG THAT CAN BE USED TO JUDGE DATA TRANSFER TIME BY COMPARING N34:10IN THE PRIMARY TO N33:10 IN THE SEC

Sample ProgramsAppendix AA-9Rung 10:3THIS IS THE PRIMARY SUBROUTINE. THIS RUNG EXAMINES THE BID REQUESTED AND THENMOVES A BLOCK OF DATA FROM N34 TO TH

Sample ProgramsAppendix AA-10Rung 11:0| BTR || BTR 1

Sample ProgramsAppendix AA-11Rung 11:3N31:0/4 IS A USER DIAGNOSTIC FLAG INDICATING A LOCAL ERROR. THE BUFFER FULL BITMAY NEED TO BE DELETED.|

Backup Concepts for the PLC-5 SystemChapter 11-5Figure 1.2PLC-5 Backup System Configuration Using 1785-BCM and 1785-BEM ModulesRemote I/O Chassis No.

Sample ProgramsAppendix AA-12Rung 11:5| USER || DEFINED

Sample ProgramsAppendix AA-13Table A.BData Table Typical Transfer Time Using Method 1 Program with Minimal Program Scan (3–8 ms)Number of BlocksBeing

Sample ProgramsAppendix AA-14Program file 9 contains the secondary subroutine. This file: checks the block ID of the BTR and copies the BTR data wit

Sample ProgramsAppendix AA-15Rung 2:1THIS RUNG DETERMINES PRI/SEC FUNCTIONALITY AND EXECUTES THE CORRESPONDINGSUBROUTINE.|

Number of blocksthat make up total segment.Sample ProgramsAppendix AA-16Rung 2:4THE BTW WILL SEND THE PACKET LENGTH, BLOCK ID AND, WHEN PRIMARY, IT WI

Sample ProgramsAppendix AA-17Rung 2:5THIS SUBROUTINE MONITORS THE BLOCK TRANSFER WRITES, READS AND READ STATUS DATAAND INCREMENTS COUNTERS ON ERRORS.

Sample ProgramsAppendix AA-18Rung 9:0THIS IS THE START OF A SUBROUTINE PROGRAM FILE THAT WILL BE EXECUTED IN THE SECONDARY PROCESSOR TO BTR AND MOVE D

Sample ProgramsAppendix AA-19Rung 9:2THIS RUNG IS A PAIR WITH RUNG 9:1.| |BTR 2

Sample ProgramsAppendix AA-20Rung 9:4THIS RUNG IS A PAIR WITH RUNG 9:3.| |BTR 3

Sample ProgramsAppendix AA-21Rung 10:0THIS IS THE START OF A SUBROUTINE PROGRAM FILE THAT WILL BE EXECUTED IN THE PRIMARY PROCESSOR TO MOVE AND BTW DA

Backup Concepts for the PLC-5 SystemChapter 11-6How the PLC-5 Backup System WorksIn the PLC-5 backup configuration, one system (consisting of one PLC-

Sample ProgramsAppendix AA-22Rung 10:2THERE IS A RUNG FOR EACH BLOCK WRITE (1–16) THAT PREFORMS THE BTW AND MOVES THEDATA FROM N34 TO THE PROPER BTW D

Sample ProgramsAppendix AA-23Rung 10:3THIS RUNG IS SIMILAR TO RUNG 10:2.| PACKET

Sample ProgramsAppendix AA-24Rung 11:0THIS IS THE START OF AN OPTIONAL SUBROUTINE PROGRAM FILE THAT IS USED FOR DIAGNOSTICS AND ERROR REPORTING. THIS

Sample ProgramsAppendix AA-25Rung 11:3N31:0/4 IS A USER DIAGNOSTIC FLAG INDICATING A LOCAL ERROR. THE BUFFER FULL BITMAY NEED TO BE DELETED.|

Sample ProgramsAppendix AA-26Rung 11:5THIS RUNG IS USED TO RESET THE ERROR COUNTERS.| USER

Sample ProgramsAppendix AA-27Rung 11:6THIS RUNG IS USED TO RESET THE ERROR COUNTERS.| USER

Sample ProgramsAppendix AA-28Rung 11:9THIS RUNG MONITORS AND COUNTS THE BTR 3 ERRORS.| BTR 3

Sample ProgramsAppendix AA-29Table A.CData Table Typical Transfer Time Using Method 2 Programwith Minimal Progam Scan (4–9 ms)Number of BlocksBeing Tr

AppendixBB-1Reference InformationThis appendix provides the following reference information:. answers to PLC-5 backup configuration questions formul

Reference InformationAppendix BB-2Q. In which slot of the local I/O chassis do I install the 1785-BEMmodule?A. We recommend that you install the 1785-

Backup Concepts for the PLC-5 SystemChapter 11-7SwitchoverShould a fault occur in the primary processor, control switches to thesecondary system in le

Reference InformationAppendix BB-3Q. How do I configure the remote I/O chassis in the PLC-5 backupsystem?A. Any valid remote I/O chassis configuration

Reference InformationAppendix BB-4Q. Can I use a 1785-BCM Series B module with a 1785-BCM SeriesA module?A. Yes, when you properly set switch 1 of the

Reference InformationAppendix BB-5Use Table B.A and Table B.B to estimate your data table transfer times.These tables provide tested values that are

Reference InformationAppendix BB-6Table B.BData Table Typical Transfer Time Using Method 2 Programwith Minimal Progam Scan (4–9 ms)Number of BlocksBei

AppendixCC-1Using a Series A 1785-BCM ModuleThis appendix briefly describes the differences between a 1785-BCMseries A backup module and a 1785-BCM Se

Reference InformationAppendix CC-2Figure C.11785-BCM Series A Module Communication Links1 Terminals 9, 10, and 11 are connected between the 1785-BCM m

IndexI-1Numbers1785-BCM modulecommunication links, 2-2compatibility, 1-7customer relay, 2-5features and capabilities, 1-6hardware, 2-1installation pro

IndexI-2data table data transfermethod of, 5-3sequence of, 5-3data transferdata in the data table, 5-2overview, 1-5remote input data, 5-1default commu

IndexI-3problem instructionsblock transfer, 7-12counter, 7-10diagnostic, 7-11FIFO, 7-11file arithmetic and logic, 7-11message, 7-12relay logic, 7-9seq

IndexI-4Ssample programstransferring data multipleblocks at a time, A-13transferring data one block at atime, A-1secondary processor remoteprogramming

Backup Concepts for the PLC-5 SystemChapter 11-8 transfer of control from the primary processor to the secondary whenone of the following conditions

5 1995 Allen-Bradley Company, Inc.PLC is a registered trademark of Allen-Bradley Company, Inc.PLC-5 is a trademark of Allen-Bradley Company, Inc.Data

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Chapter 22-1Understanding the 1785-BCM Hardware ComponentsThis chapter describes the major components that make up the 1785-BCMmodule. These componen

Understanding the 1785-BCMHardware ComponentsChapter 22-2All indicators light at power up or when a hardware fault occurs in the1785-BCM module. With

Understanding the 1785-BCMHardware ComponentsChapter 22-3Figure 2.21785-BCM Module Communication LinksHigh Speed Serial LinkCustomer RelayFrom Control

Because of the variety of uses for this product and because of the differencesbetween solid state products and electromechanical products, those respo

Understanding the 1785-BCMHardware ComponentsChapter 22-4Table 2.ACommunication PortsCommunication Port: This link is used to:High Speed Serial Link (

Understanding the 1785-BCMHardware ComponentsChapter 22-5Figure 2.3Relays for Processor A and Processor BPLC-5HSSLPLC-5Remote I/ODH+PLC-5HSSLPLC-5Remo

Understanding the 1785-BCMHardware ComponentsChapter 22-6There are two switch assemblies located at the top and at the bottom of the1785-BCM module. R

Understanding the 1785-BCMHardware ComponentsChapter 22-7Through its connection with the I/O chassis backplane, the 1785-BCMmodule can execute block t

Chapter33-1Installing Your PLC-5 Backup SystemThis chapter provides an overview of an installed PLC-5 backup systemand describes procedures for instal

Installing Your PLC-5 Backup SystemChapter 33-2Figure 3.1PLC-5 Backup System ConfigurationHSSL1771 –P4SPower Supply1785 –BCM Module1771 –P4SPower Supp

Installing Your PLC-5 Backup SystemChapter 33-3The logic circuit of the 1785-BCM module is driven by a power supplythrough the backplane of the I/O ch

Installing Your PLC-5 Backup SystemChapter 33-4The I/O chassis switch assembly is located on the left side of the chassisbackplane. Table 3.B lists t

Installing Your PLC-5 Backup SystemChapter 33-5Table 3.CTerminate PLC-5/15 or -5/25 Backup System DH+ and Remote I/O LinksSet SW3switchTo this positio

Installing Your PLC-5 Backup SystemChapter 33-6Keying Your I/O ChassisUse the plastic keying bands, shipped with each I/O chassis, to key thechassis s

Summary of ChangesSummary of ChangesThis release of the publication contains new updated information.To help you find updated information in this rele

Installing Your PLC-5 Backup SystemChapter 33-7The 1785-BCM series B module switch assembly SW1 is preset at thefactory to operate: with another 1785

Installing Your PLC-5 Backup SystemChapter 33-8When: To this position:Set this switch:switch 3 is always unused 3 OFF (opened)switch 4 is always unuse

Installing Your PLC-5 Backup SystemChapter 33-9Table 3.FConfiguring 1785-BCM Series B Channels 1A and 1B using SW2Configure Channel 1A switches1Config

Installing Your PLC-5 Backup SystemChapter 33-101. Turn off power to the I/O chassis.2. Place the module in the plastic tracks on the top and bottom o

Installing Your PLC-5 Backup SystemChapter 33-11Figure 3.51785-BCM Module ConnectionsBlueClear1239101112131415161718192012391011121314151617181920Chas

Installing Your PLC-5 Backup SystemChapter 33-12Connecting the 1785-BCM ModulesConnect the High Speed Serial Link (HSSL) to establish communicationbet

Installing Your PLC-5 Backup SystemChapter 33-13Making Remote I/O ConnectionsFigure 3.7 shows Channel 1B configured to establish communication withthe

Installing Your PLC-5 Backup SystemChapter 33-141. Connect one end of a 1770-CD cable to the REM I/O connector onone of the PLC-5 programmable control

Installing Your PLC-5 Backup SystemChapter 33-153. Perform steps 1 and 2 for the other PLC-5 programmable controllerand 1785-BCM module.4. Connect a 1

Installing Your PLC-5 Backup SystemChapter 33-16Figure 3.10Remote I/O Connections Added Between 1785-BCM Module and Remote I/O Adapter ModuleLocal I/O

PrefaceiUsing This ManualThis manual shows you how to use 1785-BCM series B backup communicationmodules with a PLC-5 programmable controller (PLC-5/15

Installing Your PLC-5 Backup SystemChapter 33-176. Connect the other end of the 1770-CD cable to terminals 1, 2, and 3on the wiring arm of the Rermote

Installing Your PLC-5 Backup SystemChapter 33-181. Connect one end of a 1770-CD cable to the PEER COMM INTFCconnector on one of the PLC-5 programmable

Installing Your PLC-5 Backup SystemChapter 33-192. Connect the other end of the 1770-CD cable to terminals 12, 13, and14 on the wiring arm of the 1785

Installing Your PLC-5 Backup SystemChapter 33-205. Connect the 1770-CD cable from the Data Highway Plus network to9, 10, and 11 on the wiring arm of o

Chapter44-1Installing Your 1785-BEM ModuleThis chapter: describes the 1785-BEM backup expansion module identifies major components of the 1785-BEM m

Installing Your 1785-BEM ModuleChapter 44-2Status IndicatorsThe 1785-BEM module has two status indicators on the front panel of themodule (Figure 4.1)

Installing Your 1785-BEM ModuleChapter 44-3Wiring ArmYou make connections to your communication links with the 1771-WGwiring arm, which is shipped wit

Installing Your 1785-BEM ModuleChapter 44-4As shown in Figure 4.2, there are two user-configurable ports (Channels2A and 2B) that support remote I/O o

Installing Your 1785-BEM ModuleChapter 44-5Figure 4.3Relays for Processor A and Processor BPLC-51785-BEM 1785-BEM1785-BEM 1785-BEMProcessor A (primary

Installing Your 1785-BEM ModuleChapter 44-6Switch AssemblyThe 1785-BEM module has a switch assembly which specifies if Channels2A and 2B are going to

PrefaceiiIf you want to read about: Refer to chapter:two methods you can use to program your backup system;considerations for using instructions that

Installing Your 1785-BEM ModuleChapter 44-7The installation procedures for the 1785-BEM backup expansion moduleare: determining power supply requirem

Installing Your 1785-BEM ModuleChapter 44-8Figure 4.4PLC-5 Backup System Configuration (using a 1785-BEM module)Remote I/O Chassis No. 1Remote I/O Cha

Installing Your 1785-BEM ModuleChapter 44-9Electrostatic Discharge DamageATTENTION: Under some conditions, electrostatic dischargecan degrade performa

Installing Your 1785-BEM ModuleChapter 44-10Setting the 1785-BEM Module Switch AssemblySwitch assembly SW2, located at the bottom of the 1785-BEM modu

Installing Your 1785-BEM ModuleChapter 44-11Table 4.BConfiguring Channels 2A and 2BConfigure Channel 2A switches1Configure Channel 2B switches2for: 14

Installing Your 1785-BEM ModuleChapter 44-121. Turn off power to the I/O chassis.2. Place the module in the plastic tracks on the top and bottom of th

Installing Your 1785-BEM ModuleChapter 44-13Figure 4.71785-BEM Module ConnectionsBlueClear1239101112131415161718192012391011121314151617181920Chassis

Installing Your 1785-BEM ModuleChapter 44-14Making Channel 2A ConnectionsFigure 4.8 shows the Channel 2A connections you must make for yourPLC-5 backu

Installing Your 1785-BEM ModuleChapter 44-15Figure 4.9Channel 2A Connections Added Between a PLC-5 Processor and 1785-BEM ModuleLocal I/O ChassisLocal

Installing Your 1785-BEM ModuleChapter 44-164. Connect a 1770-CD cable to terminals 9, 10, and 11 on each of the1785-BEM wiring arms as shown in Figur

Prefaceiii Switchover is the transfer of I/O control from the primary processor to thesecondary processor. Bumpless switchover is the transfer of I/

Installing Your 1785-BEM ModuleChapter 44-175. Connect the 1770-CD cable from the Data Highway Plus network orRemote I/O link to 9, 10, and 11 on the

Installing Your 1785-BEM ModuleChapter 44-18Figure 4.12Channel 2B Connections1771 –P4SPower Supply1771 –P4SPower Supply1785 –BCM ModuleLocal I/O Chass

Installing Your 1785-BEM ModuleChapter 44-19Figure 4.13Channel 2B Connections Added Between a PLC-5 and a 1785-BEM Module1771 –P4SPower Supply1771 –P4

Installing Your 1785-BEM ModuleChapter 44-204. Connect a 1770-CD cable to terminals 15, 16, and 17 on each of the1785-BEM wiring arms as shown in Figu

Installing Your 1785-BEM ModuleChapter 44-215. Connect one end of a 1770-CD cable to terminals 15, 16, and 17 onthe wiring arm of one of the 1785-BEM

Chapter 55-1Operating Your PLC-5 Backup SystemIn this chapter we describe how the primary system transfers data to thesecondary system. We do this by

Operating Your PLC-5 Backup SystemChapter 55-2Figure 5.1Automatic Transfer of Data Over Remote I/OHSSLPrimary SecondaryPLC-5 PLC-51785-BCM 1785-BCMRem

Operating Your PLC-5 Backup SystemChapter 55-3Sequence of TransferThe sequence of transfer from the primary to the secondary system is asfollows:1. Th

Operating Your PLC-5 Backup SystemChapter 55-4This scheme, where status and block identification information are alwayspresent, permits continuous ver

Operating Your PLC-5 Backup SystemChapter 55-5Important: When programming block transfer instructions, you must specifythe LENGTH field (Figure 5.3) a

Table of ContentsIChapter 1Chapter Objectives 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why Use a Backup System? 1-1. .

Operating Your PLC-5 Backup SystemChapter 55-6Figure 5.4BTR Instruction Words15 14 13 12 11 10 09 08 07 06 05 04 03 03 01 00REMOTE STATUSLOCAL STATUSB

Operating Your PLC-5 Backup SystemChapter 55-7Status DescriptionBit8 Serial communication error; when on, this bit indicates a communicationerror in t

Operating Your PLC-5 Backup SystemChapter 55-8When the primary 1785-BCM module receives the last block (block ID =number of blocks in segment) through

BitsWord 2Word 1. . . Word 64Word 311057IOperating Your PLC-5 Backup SystemChapter 55-9Figure 5.5BTW Instruction Words15 14 13 12 11 10 09 08 07 06 05

Operating Your PLC-5 Backup SystemChapter 55-10With 1785-BCM module, 32 input bits are available in the PLC-5 processorimage table. (The 32 output bit

Operating Your PLC-5 Backup SystemChapter 55-11Table 5.CExtended Status Bits (W1)Bit1Description10 1785-BCM series A module; when on, this bit indicat

Operating Your PLC-5 Backup SystemChapter 55-12Each byte of word W2 is divided into two groups of four bits corresponding tothe module’s channels (Fig

Operating Your PLC-5 Backup SystemChapter 55-13This means that if you set both processors node addresses to n, theprogramming device can communicate w

Operating Your PLC-5 Backup SystemChapter 55-14To provide status information, or to pass additional block transfer values, youmust provide support lad

Operating Your PLC-5 Backup SystemChapter 55-15Figure 5.9Execution of Primary ProgramBTRBTWBlock ID = 164 wordsPrimary ProcessorPrimary 1785-BCM modul

Table of ContentsIIChapter 5Chapter Objectives 5-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How the 1785-BCM Module Operat

Operating Your PLC-5 Backup SystemChapter 55-16The primary 1785-BCM module sends several data blocks that make up asegment sent to the secondary 1785-

Operating Your PLC-5 Backup SystemChapter 55-17For example, if the primary processor is sending multiple blocks to thesecondary processor, the data th

Operating Your PLC-5 Backup SystemChapter 55-18After you have checked your program for proper data to be transferred, andhave developed the transmitti

Operating Your PLC-5 Backup SystemChapter 55-19If a power loss occurs in both the primary and secondary systems once thebackup system has been started

Operating Your PLC-5 Backup SystemChapter 55-20Once a faulted system has been repaired, you may restart it as described below.You do not need to power

Operating Your PLC-5 Backup SystemChapter 55-21To avoid a control switch from the primary to the secondary processor whenyou attempt to edit the ladde

Chapter 66-1Switchover ConsiderationsWhen planning programs for the PLC-5 backup system, you must firstconsider that the program scans of the two proc

Switchover Considerations Chapter 66-2Input Signal Update TimeImmediately after the switchover, it is possible that the secondaryprocessor will be rea

Switchover Considerations Chapter 66-3Using the 1785-BCM module, the primary system can transfer data to thesecondary system at a maximum throughput o

Switchover Considerations Chapter 66-4Backup communication functions provided by the PLC-5 backup systemdo not transfer the force tables from the prim

Table of ContentsIIIAppendix AAppendix ObjectivesA-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method 1 Sample – Tr

Switchover Considerations Chapter 66-5The other stations on the link initiate a token recovery procedure whichincludes: recreating the active node ta

Switchover Considerations Chapter 66-6Table 6.ADH+ Switchover ScenariosIf the new primary is: the following could occur causing this resultPolling the

Switchover Considerations Chapter 66-7The secondary processor (remote I/O scanner or adapter) is not part of theremote I/O link, but is communicating

Switchover Considerations Chapter 66-8Figure 6.1Block Diagram of Remote I/O Switch1785-BCMCopy of remote I/O data including blocktransfersSecondary pr

Switchover Considerations Chapter 66-9Several of the data table sections in the PLC-5 processor are not structuredwith single 16-bit words. You need

Switchover Considerations Chapter 66-10Because the secondary processor’s program scan and block transferexecution are totally asynchronous, it is poss

Switchover Considerations Chapter 66-11Should the 1785-BCM module transfer one or more of these values to thesecondary system and the primary system f

Switchover Considerations Chapter 66-12In this chapter, you read about switchover considerations for the PLC-5backup system. By accounting for these

Chapter 77-1Programming TechniquesRead this chapter to familiarize yourself with techniques used to program yourPLC-5 backup system.In this chapter we

Programming TechniquesChapter 77-2Figure 7.1Minimum Program to Transfer Data Table Values (put this program in both processors)1771–BCM GETTING STARTE