Rockwell Automation 1785-BCM_BEM, D17856.5.4 PLC-5 Backup Communication Module User Manual - Manual (Page 16)

Backup Concepts for the PLC-5 System
Chapter 1
1-8
transfer of control from the primary processor to the secondary when
one of the following conditions is detected by the secondary processor:
- communication timeout in the High Speed Serial Link (HSSL)
between the two 1785-BCM modules and primary system is not
updating the remote I/O
- transfer of control command from the primary 1785-BCM module
substitution of equipment without interruption of the process; that is, the
faulted system can be repaired while the other system is controlling the
process
connections for remote I/O and Data Highway Plus network (the
1785-BCM module routes the remote I/O network and the Data
Highway Plus network to the active processor)
isolation of the systems, in order to guarantee that a fault in one system
does not affect the other
diagnostics information
remote programming capability for secondary processor
capability of switching up to four configurable communication channels
when using the 1785-BEM backup expansion module
Backup Expansion
The 1785-BCM module has two channels. The PLC-5/40 and PLC-5/60
processors have four communication channels. You can provide the backup
of the other two processor channels by adding the 1785-BEM backup
expansion module. For more information about the 1785-BEM backup
expansion module, refer to Chapter 4.
Compatibility
The 1785-BCM series B backup module is compatible with the 1785-BCM
series A backup module when you properly configure switch assembly
SW1 and switch assembly SW2 of the series B module.
This chapter provided an overview of backup concepts and the PLC-5
backup system. Read chapter 2 to understand the 1785-BCM module
hardware components. What to do Next