Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 72)

Publication 1785-UM024B-EN-P - January 2003
5-8 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System
This puts the system in a state where the secondary processor controls
some outputs and the primary processor controls the remaining
outputs. This system state may not be acceptable in certain
applications.
Output ownership verification is done via a round-robin poll that runs
in the background of the primary processor.
For example, if there are 20 redundant connections in a system, the
primary processor polls these connections starting with redundant
connection 1, then 2, then 3 and so on, until it has polled all 20
connections. If the primary processor has lost any of these 20
connections, output ownership verification places this value in register
08 of the ControlNet Backup Integer File. This register is written over
at the completion of every polling cycle, and contains a count related
only to the last polling cycle. The value in register 08 will always be -1
(FFFF Hex) in the secondary processor.
To be notified of this value, your application must poll register 08 in
the ControlNet Backup Integer File on a continuous basis in the
primary processor. If the value in this register is non-zero, the
application should notify the system operator to cycle power to the
secondary processor which restores output control to the primary
processor.
ControlNet Backup
Configuration and Status
File The data table file number of the ControlNet Backup Configuration
and Status file can be found in the PLC-5 processor at word S:67. The
default configuration parameters in this file are initialized, when the
file exists, the value in S:67 is correct, and at least one of the three
connection parameters (i.e., one of the first three words of the file) is
invalid. The ControlNet Backup Configuration and Status file consists
of 200 words, as defined in the following table.
IMPORTANT
To be notified of this system state, you must poll the
output ownership verification feature.
Word Definition
0 Odd node address of the odd/even pair of node addresses for the two
PLC-5 backup processors.
1 Message number of the scheduled Backup Handshake connection being
sent from the processor at the Odd node address.
2 Message number of the scheduled Backup Handshake connection being
sent from the processor at the Even node address.