Rockwell Automation 1785-BCM_BEM, D17856.5.4 PLC-5 Backup Communication Module User Manual - Manual (Page 84)

Operating Your PLC-5 Backup System
Chapter 5
5-20
Once a faulted system has been repaired, you may restart it as described below.
You do not need to power-down or change the mode of the operating system to
restart the system.
1. Switch the repaired processor to PROGRAM mode and apply power. This
way, the processor automatically becomes the secondary (backup).
2. Load the memory of the secondary processor and the I/O configuration
through node n+1 by using a programming device connected to the Data
Highway Plus link.
ATTENTION: Ensure that key data table values are identical in
both processors. If this is not accomplished, unpredicted machine
motion could result when you transfer from primary to secondary
processor.
3. Switch the backup processor to RUN mode.
The 1785-BCM Backup Control Module does not control the operating mode
(PROGRAM/RUN) of the primary and secondary PLC-5 processors. Thus, if it
is necessary to change the operating mode of the processor, change the mode of
the secondary processor first. Then change the mode of the primary processor.
Always change the mode of the secondary system first; if both processors are in
RUN mode, and if the primary processor is switched to PROGRAM mode first,
the primary processor transfers control of the I/O to the secondary system.
Remote Test-Mode
To initiate remote test-mode on a processor in backup configuration (using a
1785-BCM series B module), perform the following steps.
1. Take the secondary processor off-line by removing power or placing the
secondary processor in program mode.
2. Initiate the remote-test mode command to the primary processor.
When the primary processor is in remote-test mode, the outputs are disabled.
Restarting a Repaired Backup
System
Switching the Processor’s
Operating Mode