Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 - Manual (Page 39)

Installing a Backup System
Chapter 2
2-24
To implement MX backup you need two 1775-MX memory
communication modules, one for the primary processor and another for the
backup processor, and one 1775-CM memory communication cable
assembly. The cable assembly consists of four cables. Two of them are
interconnect cables (3 feet long) that eliminate the need for a 1775-CBA or
1775-CBB backup cable. The other two cables are communication cables
(30 feet long).
Figure 2.18 shows the connections required for MX backup.
Figure 2.18
Connections for MX Backup
Primary Processor Backup Processor
12187
RCVG
XMTG
RCVG
XMTG
Memory Communication Cable Assembly (cat. no. 1775-CM)
Interconnect
Cable
Configuring 1775ĆMX Memory
Communication Modules