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After a Modbus device have been offline and comming back online a strange Message is sent from the AS to the Modbus device.

Issue

After a Modbus device have been offline and comming back online a strange Message is sent from the AS to the Modbus device which looks like this:

WriteData TX on /dev/tac_comporta:  01 2B 0E 01 00 70 77
ReadData RX on /dev/tac_comporta:  01 AB 01 9E F0

This message cause the Modbus device to restart, is it possible to disable it?

Environment

StruxureWare Building Operation 1.5

Cause

This is a new feature added in 1.5, its purpose is to read the devices identification (0x2B). It works by polling this FC, if it don’t get a valid reply to this message it don’t try anymore as it assumes it’s not supported by the device. This is usually not a problem but we have seen that some Modbus devices van't handle this message and stops communicating with the AS or ES.

Resolution

It can’t be disabled, however if you turn off the device polling it won’t send that FC, so a sort of workaround.
To turn of the device polling open properties and set "Poll interval" to "Inhibit".

The problem with this workaround is that the online detection for the device is turnd off, so the device will never go offline in SBO.

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Revision #:
1 of 1
Last update:
‎2018-09-11 10:25 AM
Updated by: