Hello,

pls explain your problem, include info about your HW (order numbers) and your Automation SW. You can zip screeshots of your HW cfg and code where your comm instructions are located. This kind of problem can be started from more options. In any other case monitoring output signals of instructions can help to find problem.

Hello,

what happen when you set REQ to false? MB_State in Static change to 0? What about that Modbus Simulator, did you set all parameters as they need to be set? In other case swap A and B wires, this can be common problem.

Update: another solution is (what was also reported from users) set initial state of line to value 2. This is in DB of Comm_Load -> LINE_PRE parameter.

Hello,

again pls, what about that MB_STATE value when you set REQ to false, it change to 0? If not, you're in unstable state and you need reset that value in MB_STATE to 0. Then you can start your requests again.

Update: to be also 'in' to this problem, try connect simple Hyperterminal PC application and check incomming message structure from PLC. If you can check this in your now MB sim try in that. You can easy detect if your incoming message is correct due your settings on MASTER block.

Hello,

pls read my previous post about update, maybe can be helpful to start with this. Did you look to ERROR and STATUS outputs? In case of ERROR, save STATUS value to free WORD memory to see this. What also can be problem, prior to execute MASTER block your COMM_LOAD block need to be true in DONE output. If not, you can't continue with MASTER execution, only simple info for sure.

Update: pls try check SWs which can show hex representation of bytes, this can help you better check frames.