CM11A does not get ready for X10-trasmission with Programmable Logic Controller

I am trying to control an X10 installation from a Programmable logic controller (PLC S7-200) via a CM11A. For test purposes there are only A2 (AM12) and A5(LM15) installed.

The following work without any problem:

-Get status 8BHEX

-Write time 9BHEX

-X10 reception (5AHEX from CM11A) and subsequent response C3HEX to receive serial data buffer (Note: I occcasionaly used TM13 (as A1) and a remote control unit to trigger the serial ring on CM11A)

However when I try X10 transmission the following happens:

PLC CM11A

046eHEX //address A2 72HEX //checksum ok 00HEX // acknowledge 00HEX // not OK, ought to be the expected 55HEX

if one continues with the function

0662HEX //function A On 68HEX //checksum ok 00HEX // acknowledge 00HEX // not OK, ought to be the expected 55HEX

and A2 remains Off.

Just in case, I changed the CM11A with a brand new one. To no avail.

Both the CM11As work fine with the ActiveHome AND HomeSeer software on my PC.

I would be grateful for any suggestions. Many thanks in advance

dca