Modbus RTU communication problem between S5 PLC and provox DCS


Thread Starter


We tried to maintain communication between Siemens S5 PLC and Emerson DCS (Provox) via ModBus RTU but there was no success.
The parameters were as follows:
- baudrate "19200"
- parity "Even"
- stop bit "1"
- number of data bits "8"

I know that if simatic S7 PLC were used instead of S5 there was not such a problem. Pls. advise is that actually possible to maintain such Modbus communication between S5 PLC and DCS or is there anybody who has done it?


Daniel Chartier

Hello m. Mohavedan;

For the s5-95U you could use a CP521 with special driver ( From Siemens' website: Special driver CP521 as MODBUS slave (6ES5 897-8QA01)) to communicate as a Modbus slave. I don't know if these modules and drivers are still available, you'd have to check with your Siemens rep. Also, this only applies to S5-95U; since you don't give details on your S5 platform, I cannot garanty that similar modules + drivers are available on other S5 platforms.

Hope this helps,
Daniel Chartier