Hi guys ( could have already got into trouble there ! ) ive got an automation direct/siemens 305 plc base mish mosh of parts and have spotted a cpu with an rs232 port and a 4 pin plug labelled " bitbus " , i would like to get rid of my hand held programmer & 330-37 cpu and replace with a cpu with rs232 to talk to direct soft. is anyone familiar with a cpu with bitbus port ? is it a real cpu or a slave type unit ? Regards R.C.