Some additional info: because the Siemens S7-200 is in fact based on a Texas Instruments PLC, it is impossible to use S5 modules at the time. It is as if you were to use Allen-Bradley IO on a Siemens CPU, that's also impossible. The only way this could be done, beit in a limited way, is if both can use a common system. If Allen-Bradley IO could be used as Profibus DP slaves, and the configuration files are available in Step 7, then you could use AB IO with a Siemens CPU, provided it has a Profibus DP connection and it can act as Profibus DP master. I personally don't see that coming very soon.
Kind regards,