[Samba - Modbus RTU connection to many slaves]

Gabriel, 

Thanks for your prompt response. I've added the delay, and now it's working properly.

Regards

Martin

 

[Samba - Modbus RTU connection to many slaves]

Dear all, 

I'm programming an application on a  SM43-J-R20 PLC+HMI. I've added a  V100-17-RS4X card, in order to use RS485.

I've succesfully implemented Modbus RTU communication with a Frequency Drive. The thing is, I need to communicate with 11 of them.

The ladder logic so far uses the Modbus function blocks, as can be seen on the Modbus webinars on Unitronics page.

That is, I SET a variable (ex:MB0) , which is used for enabling the "function 06 Modbus"  block (preset holding register).  At the output of the block, I RESET that same variable, ensuring the block gets executed.  At the same time I reset MB0, I SET a new variable (MB1), which in turn is used for enabling the second Modbus block. This creates a sort of "continuous broadcast" to the drivers (which, If they don't receive a command in a certain time, trigger a failure). When the last block gets executed, the sequence restarts,

The question is, when I try to send a Stop command to one driver (for example), it takes an awful amount of time to execute the order (30 seconds or so).

I believe I may have a conflict between some of this blocks being executed at the same time. Is there a tutorial or an example where I can see how to succesfully implement Modbus communication with several slaves at the same time?

Thanks for the support.

Kind regards, 

Martin