RS232 communication

[DYL]

I am using the PLC and a Mapple 530C HMI.

Several weeks ago, I had figured the comminication thru RS232. It was really fast.

Then I used the RS232 to do the on-line monitoring to test my equipment.

Now I am ready to finalize the PLC and HMI communication and want to use the RS232. But the communication thru RS232 became really slow. I did not change the setting I had a few weeks ago.  I really do not know what is going on. Please help.

Thanks.

DYL

[support]

You have to asscertain that your program is not writing out of the RS232 port in any command. Any function such as PRINT, OUTCOMM, READMODBUS, WRITEMODUS, NETCMD$ etc will intrrupt the communication between the Maple and the PLC.

The best way to test if there is anything wrong with the PLC program is to put in a simple program or halt the PLC execution. If the Maple still communicate with the PLC very slowly, then it could be a communication issue between the Maple and the PLC. You will need to check if the handshake lines in the Maple are properly looped back etc.

[DYL]

Mapples update their software. It is that update that made the RS485 comminucation fast with less interuptions, and at the same time made the RS232 slower and more interuptions.

Right now, I am using the RS485.

I notice from your notes above, that readMobus or wrtiteMODbus can interrupt the communications. It is truth also for RS485, if I use readmodbu to communicate between PLC and PLC, then the communication between PLC and OIT will be interupted?
thanks.
DYL

[support]

That's right. At any one time there can only be one master. If Maple OIT is connected to the RS485 then it is the master and the PLCs have to be slave. So it may still be better to use the OIT on RS232 while leaving the RS485 for PLC to PLC communications.