Problem with COM_MOD_MAST in AC500!

2020-02-27T21:33:32.339000Z

occam hat geschrieben:
The manual says: "After completing or aborting the processing (due to an error), DONE is set to TRUE for one cycle." - no idea what does cycle mean in this case?!?!

You have to do then check for DONE and ERR in program B.
a Cycle in this case is at then from fiste time it hit COM_MOD_MASTER to then then next time..

Flændsdal

Problem with COM_MOD_MAST in AC500!

2020-02-27T21:33:28.229000Z

Hi all!
I'm having a hard time using the MODBUS RTU interface on the AC 500 and would appreciate any hint:
The application is running several programs (POUs) written in ST.
Program A (cyclic, priority 20, @ 500 ms) implements a set of synchronization flags and CASE statement used to select different Modbus requests and feed them to the COM_MOD_MAST block in program B and set the event triggering program B.
Program B (event triggered, priority 10) basically consists of a COM_MOD_MAST block and some synchronization logic to notify program A that the request is processed.
So far everything runs fine, but when I cut the RS485 connection to any/all of the MODBUS slaves DONE and ERR in the COM_MOD_MAST are not affected, and regardless of the TIMEOUT parameter the COM_MOD_MAST gets executed immediately (I measured the time before and after the COM_MOD_MAST it's < 1 ms). When I set a breakpoint at the statement containing the COM_MOD_MAST the DONE and ERR parameters are set correctly, but at the next statement they are gone. I tried assigning DONE and ERR to global variables:

MBTxRq(EN:= TRUE,
      COM := 2,
      SLAVE := MBSlaveDvADR,
      FCT := FunctCode,
      TIMEOUT := MB_COMM_TOUT,
      ADDR := MBSlaveRqAddr,
      NB := MBRxLngth,
      DATA := MBRxDataAdr,
      DONE => Mod_Done,
      ERR => Mod_Error,
      ERNO =>Mod_ErrNum
);

without success. Waiting for MBTxRq.ERNO to get nonzero was no help either.
Even using F_TRIG/R_TRIG available in the library in order to capture ERR and DONE was no cure.
The manual says: "After completing or aborting the processing (due to an error), DONE is set to TRUE for one cycle." - no idea what does cycle mean in this case?!?!
Thnx in advance!

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