Rockwell Automation AADvance Controller Troubleshooting and Maintenance Manual - Manual (Page 35)

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Document: 553634
(ICSTT-RM406F_EN_P) Issue: 089:
3-13
Check: the module PST value is it set to the correct value or has it been left at
zero.
Check: the communication link between the processor module and the I/O
module (possible I/O base unit fault or loose bus cable)
I/O Module Channel Degradation and Shutdown
Process Safety Time
Each simplex module (or group of modules) has a defined process safety time (PST), which determines
the maximum length of time that can elapse between successive reporting of channel values to the
application before the channel is declared faulty. The module PST is usually the same as the system
PST, however, it can be set to a different value within the AADvance Workbench when the controller
is first configured, or later changed by an on-line update.
 The minimum PST value for a module is 20ms and the maximum 60,000ms (1
minute).
Input Module Non-degraded Status
Degradation for input modules is on a channel-by-channel basis. A channel is considered not degraded
when when all the modules in a group are on-line and none of them are reporting a fault for the
particular channel. The Workbench reports the module status variable 'Discrepancy' as FALSE.
 A non-degraded simplex module configuration reports the channel values to the
application.
 A non-degraded dual module configuration reports the channel values to the
application based on the count value from either module.
 A non-degraded triple module configuration reports the values from any of the
three channels in the group.
Input Module Degraded Status
A channel is considered fully degraded when no modules in a group are reporting values for that
channel, or there is a fault reported on that channel for all modules in the group and either condition
exists for longer than the PST. The module status variable 'Discrepancy' is reported as TRUE and the
module reports 'safe' values back to the application for the faulty channel.
Output Module Shutdown
When an output module does not receive updated command values from a running application within
the PST, it automatically enters a shutdown mode. This action applies to all situations when
commanded state updates are not received, including communication errors, lack of processing
modules, and stopping an application.
Degraded Input Channel Reporting Values