usb to 232 comunication cable

james power

Member
Join Date
Jun 2002
Posts
3
hello all thank you for just reading my problem .
Ihave bought a new lap top and need to connect to an modicon 984 compact plc which is useing modsoft .The problem is i only have two USB ports and i need an rs 232 port :( Ihave purchased a usb to rs232 converter and tryed but i cannot communicate with the PLC .My computer tells me that the device is connected correctly .
their is no response i have used the convertor on another device an it does work.My computer is a compaq presario1200 which i find has never given me any problems the convertor is a belkin usb to 232 convertor.
has any body else had this problem.Is their a dedicated cable i can purchse
regards [email protected]
[email protected]
 
This is an issue that has plagued many BUT there are solutions in most cases. You didnt state what specific PLC you were connecting too, that will help the most in providing answers

The worst case I have seen is trying to use an AB 1747 with the USB adapter...just wont work in most cases, has to do with timing issues and APCI. I solved that issue by obtaining the PCMK card.

Overall the best solution (the most expensive though) is to get PCMCIA cards if available. I have them for AB and Siemens. For GE Fanuc, AD/Koyo I have no problem connecting via USB.
 
Just a thought...

The default setting for Modicon products is RTU which uses a precise 'framing' time period to control the start of a new message frame. You must use a 'real' RS232 serial port to communicate using RTU. Most Modicon products have a means of changing from RTU (8 bit) to ASCII (7 bit) which doesn't rely on precise timing. Set the DIP switches for the comm port to ASCII configuration, change your PC serial port configuration from RTU to ASCII and give it a try.
 

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