Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 - Manual (Page 65)

Using the 1775ĆMX
Memory Communication Module
Chapter 4
4-18
Command Description Abbreviation
ENABLE COMPARE E C The memory communication module
compares a specified section of the ladder
program in the backup processor with the
corresponding section in the primary
processor on a wordĆbyĆword basis.
DISABLE COMPARE DI C The memory communication module prevents
the execution of the program compare
function.
DISABLE OUTPUTS DI O The memory communication module inhibits
the backup processor from taking control of
outputs when the primary processor faults.
ENABLE OUTPUTS E O The memory communication module allows
the backup processor to assume control of the
outputs after switchover.
LIST CONTROL LI C The memory communication module will be
controlled by selections in LIST rather than by
commands in message instructions of a
ladder program.
PROGRAM CONTROL P C The memory communication module will be
controlled by commands in message
instructions of a ladder program rather than
the selections made in LIST.
TRANSFER CONTROL T C The memory communication module forces a
switchover from the primary to the backup
processor.
STATUS ON * STAT ON The memory communication module enables
data transfer from the backup processor to the
primary processor.
STATUS OFF * STAT OFF The memory communication module disables
data transfer from the backup processor to the
primary processor.
* Supported by series A release C (or later) 1775ĆMX modules.
To modify the operation of memory communication modules, you enter
commands into the ladder program using one or more message
instructions. Figure 4.2 shows the format of a typical message instruction.
Figure 4.2
Example MSG Instruction for a Memory Communication Module
+MSG–––––––––––––––––––––––––+ |
+MESSAGE +–(EN)–+
|Control #B0:0| |
|Channel E2.14.1+–(DN) |
| | |
| +–(ER) |
| | |
| | |
+––––––––––––––––––––––––––––+ |