I do not have any idea why my MSTR control block works only in one way. Can anyone help me on this?
Please refer to my attached Visio file for details.

Thanks.

 

Can't open Viso file, however, by one way do you mean that you can write but not read? What software are you using? Modsoft or Proworx or Concept? Configuration is not difficult if you are familiar with constraints of the function.

 

The MSTR block is designed to work with Modbus Plus and Modbus TCP/IP messages and not Modbus RTU or ASCII. For Modbus messages RTU and ASCII, use the XMIT or XXMIT blocks to communicate.

 

It's been a while since I've touched Modicon, but
isn't it the XMIT instruction that's for use with
the MB port? I though MSTR was strictly for the
MB+ port (regardless of the programming software).

Anthony Kerstens P.Eng.

 

> The MSTR block is designed to work with Modbus Plus and Modbus TCP/IP messages and not Modbus RTU or ASCII. For Modbus messages RTU and ASCII, use the XMIT or XXMIT blocks to communicate. >

You can use a BM85 Bridge Mux connected to the MB+ network and then use the MSTR block to master out to a modbus ASCII or RTU remote. The BM85 has four serial ports that can be setup as master, slave, or network slave.

 

The MSTR is a MB+ network command. MB is an RS232 port master-slave. You would need to use the Xmit loadable function block in MODSOFT on the legacy controllers or the XXMIT function in CONCEPT 2.2+.

Failing that use a BM85 (Bridge mux) which will get you four MB ports from the MB+ network.

Rob E.

 

We used the mstr instruction with the modbus
port. Using Concept 2.5 and Quantum controller.