from the Automation List department...
PPI Cables
PLCs and related questions. topic
Posted by Paul Samek on 6 February, 2007 - 12:38 am

I'd like ask some question about connection programming cable. In manual was written about RS232 (USB)/PPI Multi-master. I have one cable USB (it described in manual) and I found cable with label: Isolated PC/PPI Cable. (connection as: RS232 to RS458) And it communicates with PLC. But now I want to connect with MODEM. It is possible?

Thanks for help.

Posted by Daniel Chartier on 6 February, 2007 - 11:10 pm

In the S7-200 Programmable Controller System manual (s7-200_e.pdf) there is a chapter on network comms for the S7-200. There you will find details on modem configuration (there is a wizard in MicroWin for this) and on the setup of the PPI cable dip switches. Here is a small excerpt:

Using a Telephone Modem with the RS-232/PPI Multi-Master Cable
You can use an RS-232/PPI Multi-Master cable to
connect the RS-232 communications port of a
modem to an S7-200 CPU. See Figure 7-29.
! Switches 1, 2, and 3 set the baud rate.
! Switch 5 selects PPI or PPI/Freeport mode.
! Switch 6 select either Local (equivalent to the
Data Communications Equipment -- DCE) or
remote (equivalent to Data Terminal
! Switch 7 selects either 10-bit or 11-bit PPI protocol.

Switch 5 selects operation in PPI mode or in PPI/Freeport mode. If you are using STEP
7--Micro/WIN to communicate with the S7-200 through modems, select PPI mode (switch 5 = 1).
Otherwise, select PPI/Freeport mode (switch 5 = 0).

Switch 7 of the RS-232/PPI Multi-Master cable selects either a 10--bit or 11--bit mode for
PPI/Freeport mode. Use switch 7 only when the S7-200 is connected to STEP 7--Micro/WIN with a
modem in PPI/Freeport mode. Otherwise, set switch 7 for 11--bit mode to ensure proper operation
with other devices.

Switch 6 of the RS-232/PPI Multi-Master cable allows you to set the RS-232 port of the cable to
either Local (DCE) or Remote (DTE) mode.

!! If you are using the RS-232/PPI Multi-Master cable with STEP 7--Micro/WIN or if the
RS-232/PPI Multi-Master cable is connected to a computer, set the RS-232/PPI
Multi-Master cable to Local (DCE) mode.

!! If you are using the RS-232/PPI Multi-Master cable with a modem (which is a DCE device),
set the RS-232/PPI Multi-Master cable to Remote (DTE) mode.

Hope this helps,
Daniel Chartier

Posted by Paul Samek on 8 February, 2007 - 12:32 am

I read the manual. I understand (I think how to switch cable), but the cable that I have has only 5 switch.

1,2,3 is baud;
4 = bit (10 or 11)
5 = Dte, Dce.
(all) without PPI/Free port.

My question:
Is it possible to connect with this cable?


Paul Samek

Posted by RichERich on 26 February, 2007 - 12:17 pm
That cable will work.

You set switch 5 to DCE for when connecting to the PC. Select DTE when talking to a modem. This switch is a crossover.

Posted by Marc Sinclair on 9 February, 2007 - 11:29 pm

There is a whole section in the S7-200 manual which describes the use of modems. Try to find the manual in your own language, they are all available on the Siemens website, if you're still struggling contact me offline, the address is on the website.

Marc Sinclair

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