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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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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
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
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:
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!
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