Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 User Manual
Page 98
Programming Techniques
Chapter 5
5-17
Series A, Revision D (or later) 1775ĆKA Modules
When using series A, revision D (or later) communication adapter
modules, you can either follow the guidelines previously described for
early communication adapter modules or select backup operation with the
LIST function.
Important: Do not select backup operation for multidrop modem
applications because the modem port is not disabled after a processor fault.
If you select backup operation, you must assign the same station address to
both communication adapter modules. Even though they have an identical
station address, the backup processor modifies its station number
automatically before and after switchover.
To implement backup operation, follow these steps:
1.
On both communication adapter modules, set option switch 2 OFF.
This causes the Data Highway port on the communication adapter
module in the primary processor to deactivate when automatic
switchover occurs.
WARNING: To guard against personal injury and damage to
equipment, make sure switch 2 is set correctly. If not, both
communication adapter modules will assume the same station
address at switchover causing a data highway communication
shut down. This may cause unpredictable machine motions.
2.
Use the LIST function to disable the modem and the Data Highway
ports. This allows you to change the LIST options of the
communication adapters.
3.
Use the LIST function to select backup operation for the
communication adapter modules in both the primary and backup
processors.
4.
Use the LIST function to assign the same Data Highway station
address to the communication adapter modules in both the primary
and backup processors. Legitimate station addresses range from 000
8
to 276
8
and 300
8
to 376
8
.
Important: Never give the 1775-KA module the reserved station address
of 377
8;
and, when you select the backup operation, you cannot give the
module a station address of 277
8
.