Siemens S7-400 Profibus Communication

Hi All i need you help

i have siemens Siemen S7-400 CPU , and i want to communicate it with S7-300 IO Modules on Profibus Any help would be appreciate as if i have to fetch an analog value from it

There are two ways to do it that come to mind.

1 Master/Master using a DP/DP coupler. This is a device that communicates with both PLC over profibus and uses common memory model where information is written by on plc and read by the other.

2 Master/Slave. This would require a spare Profibus connector on one of the PLCs that can be configured as a slave.

Both methods require changes to the hardware configuration and the writing of code to pass data.

https://support.industry.siemens.co...-400-(master)-with-step-7-v5.3?dti=0&lc=en-US

Nick

Your 400 PLC, is it set up with redundancy? If so, you would need an Y-link.
Do you already have equipment hooked up to it through profibus?
This 300 station, you say IO. Does this mean you only have the IO modules? If so you would need a remote rack or even CPU.

There is a another possibility to the ones mentioned above, No DP, it would allow you to send/receive data directly over the profibus line using S7.

Please do tell us more about your system so we can help you better.