Why does my HMI return wrong object using modbus FC04 on a M580 CPU (OS3.1 and 3.2)?
description du problem
Historicaly, if an HMI wished to read a %MW or %M object, in a Premium CPU, the HMI was adressing a modbus request "FC04" to the CPU. If the number of %IW and %I configured in the CPU was equal to "0", the modbus server of the CPU accessed to %MW and %M area. => The modbus server of the CPU delivered %MW and %M.
If the number of %IW and %I configured in the CPU was not equal to "0", the modbus server of the CPU accessed to %IW and %I area. => The modbus server of the CPU delivered %IW and %I.
To avoid any migration problem from Premium to M580, we have kept the same rule on the PLC range M580.
The problem is that if a client select in CE15.0 a CPU BMEP58xx20 OS 3.0 or 3.1, the minimum value of %IW and %I has been change to a value different of "0". So the HMI received %I objects instead of %M.
by consequence the HMI doesn't get the expected object!
This different behavior will be fixe in the next version of CE15.1.
Historicaly, if an HMI wished to read a %MW or %M object, in a Premium CPU, the HMI was adressing a modbus request "FC04" to the CPU. If the number of %IW and %I configured in the CPU was equal to "0", the modbus server of the CPU accessed to %MW and %M area. => The modbus server of the CPU delivered %MW and %M.
If the number of %IW and %I configured in the CPU was not equal to "0", the modbus server of the CPU accessed to %IW and %I area. => The modbus server of the CPU delivered %IW and %I.
To avoid any migration problem from Premium to M580, we have kept the same rule on the PLC range M580.
The problem is that if a client select in CE15.0 a CPU BMEP58xx20 OS 3.0 or 3.1, the minimum value of %IW and %I has been change to a value different of "0". So the HMI received %I objects instead of %M.
by consequence the HMI doesn't get the expected object!
This different behavior will be fixe in the next version of CE15.1.
Released for: Schneider Electric USA
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