Siemens s7/200 PPI protocol description


Thread Starter

Jaroslav Tomka

I found on Search engine of AltaVista discussion concerning PPI protocol description with contact to site. I have the same problem:
Former using communication to OMRON CPM2 and changing PLC to Siemens S7/200 i don't know, how to commumicate with it. Some dll's are accessible to solve this problem, but I need only know ASCII sequence to send to COMx, witch tells PLC to send some bytes back to PC - READ partial content of V-memory and ASCII sequence to WRITE some data to PLC's V-memory (with appropriate control Char's). Thank You !
the PPI protocol is functionally similar to Omron HostLink, but unlike HostLink, is unnecessarily complicated in its messaging sequence and is not free: if you look at previous discussion on this same site, you will know that Siemens asks some 3000USD just to let you have the hardcopy of the specifications, and with a lot of nondisclosure agreements to sign. Being an user of both S7-200 and Omron PLCs, i try whenever i can to use the latter, just because the protocol for communication is freely avaliable and described in detail.

If you do not want to spend your money on a ActiveX control, the only way to proceed may be to use a port sniffer while connecting the S7-200 with MicroWIN, and note the sequence of command and response. A good and free port sniffer is available at, or you may connect at, the guy here is very knowledgeable about Siemens HW and he posted an introductory document on his experience with the protocol.