2-wire comm for s7-300

hallo to all,
I am searching for an example programm for the 2-wire communication between two S7-300 with CP341 (over a Westermo Leased Line Modem TD29). I´m newbie on this soft an my problem is the collision of the data packages.
So, has anybody an example to program an handshake between the two cpu´s?

best regards
erwin

I have no experience with CP341, but if your problem is that data is lost because both tries to send at the same time (data collision) then I have two suggestions:

1. Let one CP be the master. The "slave" can only respond right after the "master" has finished sending a telegram (I think this is the easiest way).

2. If you can detect that a datacollision has occurred: Halt the data transmission of both CP's and restart it again after a time. The trick: let the delay time be different for the two CP's. This is the same approach as CSMA/CD that is used for ethernet.

Hi...

Sorry, but the CP341 is not a high-seed serial communication??, in this case this is not the best method to comunicate 2 PLC's.. I think so..

You need to ude or CP 342-5 or Cp 343-5 L2 or Profibus in other case you can use CP 343-1 H1 or Industrial Ethernet..

I hope this help

Hello;
we are working presently on a remote pumping station project, in which we have established redundant comms over leased-line modems. We are using 2 CP 340 communication processors on each CPU (315-2DP) which we have configured with ASCII protocol, fixed data length (192 bytes) and no hardware flow control. We have set-up FB3 (P-Send) and FB2 (P-rcv) communication blocks in a FC10; the important thing is to trigger the P-Send block (we use a clock bit setup in the CPU as MB10, bit 6 giving us a 0,625Hz trigger), but to configure the P-Rcv block as always on (we use a Always-ON bit comnfigured in OB100).
We have had good success up to now with this configuration; we use the NDR bit of P-Rcv (along with a timer) to detect loss of comms, and it is very accurate.
You will find examples of the use of these FBs in the CP340 manual; you can download it from the Siemens Support webpage, or on the CD that com,es with nthe CP340.
Hope this helps
Daniel Chartier

Hello!
Have used the westermo TD29 with profibus connections.
(range about 3 km and 2 km)
==>Nothing but problems, you always get buscollissions and it's hard to tell why(the modeems have no monitoring possibility).
Got it to work "quit" fine only get the busfault only once every 20 seconds.
The problem is the TD29 system.
Maybe it works better with serial (point-to-point) connections.
Westermo says the modeems should work as network =>B.S
only ptp.

To continue, always use opticalconnections if possible!!
No interference problems, full speed, all protocols work.
Profibus with fiber works fine for 25 km (good fiber)!
speed up to 12 Mb/sec