Rockwell Automation 1785-BCM_BEM, D17856.5.4 PLC-5 Backup Communication Module User Manual - Manual (Page 151)

Reference Information
Appendix B
B-4
Q. Can I use a 1785-BCM Series B module with a 1785-BCM Series
A module?
A. Yes, when you properly set switch 1 of the switch assembly SW1 and
switches of switch assembly SW2 of the 1785-BCM Series B module.
(Refer to Chapter 3 for more information.)
Q. Can the 1785-BEM backup expansion module work with the
1785-BCM Series A module?
A. No. The 1785-BEM module can only work with the 1785-BCM Series
B module.
Q. Is it necessary to use the 1785-BEM backup expansion module
with the PLC-5/40 or PLC-5/60 processor?
A. It depends on your specific application. If you want to back up all four
channels of the processor, you must use the 1785-BCM Series B
module and the 1785-BEM module.
Q. Is it necessary to connect the programming device directly to the
processor port in order to program the secondary PLC-5
processor?
A. No. You must assign both the primary and secondary processor the
same node address in the Data Highway Plus link. When you set both
processors node address to n, the 1785-BCM module reserves the
following node address n+1 as an access point address to the
secondary processor, that is, this address is accessed by a
programming device in order to program the secondary processor.
Q. Is there any memory limit to the number of I/O points or to block
transfer instruction in the remote I/O link?
A. You can store up to 92 BTR instructions per remote I/O channel.
There is no limit for I/O or BTW instructions.