Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 - Manual (Page 11)

Choosing a Backup Configuration
Chapter 1
1-4
There are two backup configurations:
scanner backup (Figure 1.2) which uses only I/O scanner modules
MX backup (Figure 1.3) which uses 1775-MX memory communication
modules
How Scanner Backup Works
Figure 1.2 shows the implementation of scanner backup. The number one
scanner module controls switchover as well as backup, peer-to-peer, and
I/O communication channels.
Figure 1.2
Scanner Backup Configuration
CH2
TO/FROM
OTHER
PEERĆTOĆPEER
CHANNELS
SCANNER
MODULE #1
SCANNER
MODULE #1
B/U
CH1
CH2
CH3
CH4
B/U
CH1
CH2
CH3
CH4
PRIMARY PROCESSOR BACKUP PROCESSOR
BACKUP CABLE
BACKUP COMMUNICATION
PEERĆTOĆPEER
COMMUNICATION
I/O COMMUNICATION
CH3 TO/FROM
I/O
10972ĆI
The data table of the backup processor can be updated in three ways.
The backup processor listens only to discrete real world inputs.
The input/output buffer transfers data files over the backup
communication cable. (You must program move and move file
instructions to transfer critical data table information.)
Data Highway or Data Highway Plus communication
Choosing a Backup
Configuration