why can i not communicate with plc

hi all
just an over view first
i have a mitibishi fx1n conneted to a HMI E150 and are working well together

i have a pc with FXWIN and the correct program on the software that is in the PLC
i have a usb to rs232 cable in the pc and a rs232 cable from the convertor, to the rs232 on the HMI and a commes cabele to the HMI tot he FX1N

if i use the E100 software in the PC i can communicate with the HMI no problem
but if a tell the PC FX WIN to verifiy the program in the PLC it comms back with a COMMS ERROR why?
any halp would be good
thanks
joe

If I tell the PC FX WIN to verifiy the program in the PLC, it comms back with a COMMS ERROR. Why?

Click to expand...

The FXWIN programming software could not establish a communications connection with the Mitsibushi FX1N PLC. It could be that the E150 HMI has tied up the USB-to-RS232 port, so that the PC has no other way to communicate with the PLC.

In the past, I have worked around the problem by only communicating with one device at a time. If your PC supports multiple USB ports, then adding a second USB-to-RS232 converter (for the PLC connection) might solve the problem.