REXYGEN Community Forum

oza77

Member

Registered: 2017-05-11

Posts: 2

REX+S7 via Modbus

Hi, I'd like to use Modbus to communicate with S7-1200 instead of S7Drv, which is a great driver, but inconvinient for fast processes (2ms sampling period) as it causes 8ms delay on the line in our case even if configured as fast as possible.

Is it possible to talk to PLC via Modbus at all?

S7 block needs specification of so called CONNECT_ID both on MB_server and MB_slave.

Does any of REX modbus configuration parameters match CONNECT_ID? 

Here are the screenshots of PLC project:

[https://www.rexcontrols.cz/forum/img/members/155/5.png]

[https://www.rexcontrols.cz/forum/img/members/155/1.png]

[https://www.rexcontrols.cz/forum/img/members/155/3.png]

Thx, Stepan

jaroslav_sobota

Administrator

Registered: 2015-10-27

Posts: 535

Re: REX+S7 via Modbus

Hi Stepan,
Modbus TCP communication with S7 PLCs is definitely possible. Make sure to use the appropriate function block (MB_CLIENT=Modbus master, MB_SERVER=Modbus slave).

If I understand the documentation correctly, the CONNECT_ID is an internal variable and has no effect on communication parameters (and corresponding settings in REX).

In any case, I'm eager to know what sampling rate you'll be able to achieve.

Best regards,
Jaroslav

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