Safety PLC interfacing

Hey Guys,

Just a quick question, how do I interface a positioning sensor with an RS 485 interface with an OMRON SAFETY PLC, which has a RS 232 interface but not a RS 485 interface.

P.S Its an OMRON G9SP series safety PLC

Any inputs?

http://www.data-converters.com/index.php?main_page=product_info&products_id=12

just a thought. Cheaper models are available if external power is available.

Is the serial port on the PLC really meant to interface an encoder?

Yes, previously we had a similar case when we integrated a Data positioning sensor with the PLC through the RS 485. The P.S has a RS 485 out, isn't that meant to be fed to the PLC?
Please correct me if I am wrong, its completely new for me.
The PLC in concern is an OMRON CP1L and the sensor is a Pepperl and Fuchs data matrix sensor which comes in many different interfaces, SSI, RS 485 etc.

I really appreciate your help !