The user manual states that the RS232 settings are 9600, 8, N, 1. You will also find these settings by using the remote control to check them on screen. These are the internal settings between the input card and the plasma display. The settings for the Crestron port to the card are 115,200, 8, N, 1.

There are two RS232 ports on the plasma. Use the RS232 port that is next to the DVI input. The RS232 cable should be a straight through 2-2, 3-3, 5-5

In addition, we have found that the display will only take commands approximately every 15 seconds.  If you send an input switch command before then, it will say that it switched, report back that it switched when queried, but not actually switch.  In order to reliably switch every time, the display can only take commands 15 seconds apart.