TM200C40T PLC modbus in Ecostruxure machine expert -basic

savan · ‎2024-06-18

Hi everyone,

I am using TM200C40T PLC. I am new to PLC programming. I want to read modbus data continuously from slave.

I have made Ladder diagram which use READ_VAR block. I am able to read modbus data from slave but I can do it only once in start when I give high input to Execute of block. I am getting done signal from block.

after getting done signal, if data is changed from slave side I can't read updated data in READ_VAR block.

I want to continuously read data from slave.

I am attaching image of Ladder Diagram I made.

Looking forward to response.

Thanks in advance.

Bosswaffle · ‎2024-06-19

I think this block only executes once after the execution input is active, since it starts based on a rising edge. So once it is done, you'll have to toggle the execute input off for at least one scan cycle before setting it high again.

It also seems like you have both the execute and abort inputs connected the same line, so you're likely aborting the read Everytime you try to execute.You should monitor the status of the aborted output and error output to check for proper functionality. The CommError and OperError will also give you insight into what is working or not

See Answer In Context

Bosswaffle · ‎2024-06-19

I think this block only executes once after the execution input is active, since it starts based on a rising edge. So once it is done, you'll have to toggle the execute input off for at least one scan cycle before setting it high again.

It also seems like you have both the execute and abort inputs connected the same line, so you're likely aborting the read Everytime you try to execute.You should monitor the status of the aborted output and error output to check for proper functionality. The CommError and OperError will also give you insight into what is working or not