2424+ VB2008 to RS485 Serial Data Problems

[keith]

Help!

I'm having trouble successfully sending Host Link Commands from the host PC to the Com3 port (RS485) of the 2424+ PLC. I can get an ASCII string from the PLC to the host with no problems but the PLC does not seem to be able to get or act upon data from the PC. Example:
 
From a standard VB2008 Serialport1.writeline routine, I'm sending @01Wb0100FF00* + VbCr to Com3 on the PLC (Blank Program) expecting to turn on Output #1. Does not work.
 
This method always works well for me with the T100MD888, but it doesn't seem to want to cooperate on the 2424+. What I'm wondering is if there is a special setting or programming configuration that I need to make in order to set the 2424+ up for receiving HLC's via Com3. I'm probably missing something simple but I would sure appreciate any help anyone could offer. Thanks so much.

[support]

The COMM3 port on T100MD2424 works exactly the same as that found on the T100MD888+ PLC.

1) Have you tried using the TLServer to communicate with the PLC via the RS485 port? I am assuming you have some kind of USB to RS485 adapter or an Auto485 adapter that convert your RS232 interface to RS485 which allows you to test the communication with the PLC via the TLServer.

2) If TLServer doesn't work, try to set the DIP switch #4 to ON, then power recycle the PLC. The PLC should start up in the PAUSE mode, which ensure that nothing in your PLC program has modified the COMM (such as SETPROTOCOL 3, x  which disables it from responding to host link command)

3) If you can't get serial communication with the PLC via RS485 port even with DIP switch #4, then it is likely that the RS485 driver chip may be damaged and need to be replaced.