communication over leased line with Siemens S7-200 PLC


Thread Starter


Suppose I need to implement a telementry project using two standalone Siemens S7-22x (e.g. S7-226) PLC, they have to communicate over a leased line so that information on each end (e.g. I, Q, M, DB..) can be read/write by the other end, how should I do it? Is it complicated? Please do suggest any necessary equipment other than the PLC that I need to implement this. (I know I must need a modem or something)

Any help or example is appreciated.

Zan Von Flue

Included is the siemens website link that answers (i hope) this question. I work with the 300/400 series and it's no problem to exchange information. The S7-200 handbook should included more information. I also believe, take a look on the left side of the programming software (microwin32) there is a icon for comunications. It should lead you through needed steps to exchange information with the other CPU.
The example is a 212 with a 214


Lynn August Linse

PPI (the S7-200 protocol) is very timing sensitive. I cannot give an exact answer, but you'll need a modem set that adds very little delay to the signal. Unfortunately you'll have little control for delays your leased-line provider may add - they may pack your analog "leased line" into some higher-bandwidth digital circuit.

You may also need a modem which supports an 11-bit asynchronous character (meaning can send an 8-bit data byte with 1-bit of parity) as opposed to
the 10-bit asynchronous character of many commercial modems (meaning only 8-bit data with no parity or 7-bit data with parity). There may be some setting to allow use with 10-bit.

Siemens has a nice set of FAQ and Application notes on the S7-200 line - they likely have one on leased line modems.

Best Regards

Lynn August Linse, [email protected]
3 Rue Monet, Foothill Ranch CA 92610
Ph: 949-300-6337 Fx: 612-677-3253