Ethernet Master Error reporting

[russher]

The Do-More Designer HELP file indicates that ST153 "will be ON when the Ethernet I/O Master detects an error with one of its Ethernet I/O Slaves - most likely an Ethernet I/O Slave is offline".
When pulling the Ethernet cable from an Expansion Rack I can see in the I/O System View the resulting error, but ST153 remains OFF. Am I missing something?
Essentially I am looking for a way of creating an alarm in my HMI when an expansion rack is not communicating.

[BobO]

ST153 should come on unless the remote is marked as optional by the "CPU remains in RUN mode on slave error" in the configuration. If optional, the base error is not considered a master error. You can still check the status of the individual slave through the $EthIOMaster structure.

[russher]

Thanks for your reply BobO.
I am finding that ST153 only turns ON when the "CPU remains in RUN mode on slave error" is disabled - in other words, on a slave error the CPU goes to PROGRAM mode. I'm finding that this defeats the purpose as my MMI won't pick up that the ST153 is ON because the CPU is no longer in RUN.
Your suggestion, however, to use the $EthIOMaster structure - more specifically the $EthIOMaster.Error - seems to work well for creating an MMI alarm when an expansion rack goes down. I am then using the $EthIOMaster.Slave0Error to report the Last Error Code.
Thanks.