About Serial and Paralell online edits. In the parallel version the upper keyswitch on the CPU must be in the STOP position to store I/O and register tables. The ladder diagram can be changed when the cpu keyswitch is in STOP or RUN position. In the serial version the upper keyswitch on the CPU must be in STOP position to store I/O tables, register tables, and the ladder diagram to the CPU. About running under ME or XP. Neither version of Logicmaster Six will run on ME or XP as they are based on NT technology. About Serial speed vs. Paralell speed For RS-232-C the maximum data rate is approx. 20 KBaud @ 50 feet. For RS-449, RS-422, and RS-423 the maximum data rate is approx. 100 KBaud @ 4000 feet and 10 MBaud @ 40 feet For CCM1 you can use RS-232-C, Current Loop, AND RS-422 on the J1 Port (25-pin, femal, D-type connector) OR RS-232-C or RS-422 on the J2 Port (9-pin, femal, D-type connector) I'm not sure about CCM2. We don't use any.