TL server loses connection

[Vijay]

I have running a 1616+ that is doing a lot of work - running stepper,two pWM and I am using the RS232 to talk to a weigh scale at 9600 baud. I have connected the PC to the 485 using a convertor. Programs transfer fine but on-line monitoring only lasts a few seconds after which it cannot find the PLC ID. Typically I have to end the program and try again. Obviously without the on-line monitoring, troubleshooting is very difficult. I am using 5.1 and TL server 2.0.

Any ideas ?

[support]

Usually the PLC should be able to respond to communication even if it is quite busy unless it is performing near its limit such as driving the two stepper channel at 10KHz.

Are you using the Auto485 adapter for on-line monitoring or a third party RS485 converter?

Can you try transfering a simple program (e.g. blank program) to the PLC and then perform online monitoring and do you encounter the same problem of frequent lost communication? If you do encounter the same problem then it could be the PC's serial port, RS485 converter or even the RS485 driver IC on the PLC (75176) that is having compatibility or functional problem.

If you don't encounter lost communication while monitoring simple or blank program, then examine if any part of your program could be writing out to the RS485 port (e.g. PRINT #3, NETCMD$, OUTCOMM, READMODBUS or WRITEMODBUS). ?

[vijay]

I am running one stepper at up to 20 kHz. It is always moving. Two PWM.

I have no problem with simple programs.

I have tried Auto485 and third-party (B-B) with similar results.

No other commands to COMM3 or MODBUS commands.

Is there any newer PC software I should update to ?

- Vijay

[support]

Running the stepper at 20KHz means the CPU is spending much more time servicing the stepper channel than the serial comm. You may like to try to extend the timeout on the TLServer to longer time and see if the problem can be resolved.

In this case, it may be easier to debug using the LCD display to show the parameters of interest, or slow down the stepper when you need to perform debugging and then set it back to full speed when the PC is offline.

There is no further update for TLServer 2.0 at the moment. In any case this is not a software problem. It is just that the CPU need to give higher priority to servicing the stepper channel to ensure that the output waveform is an acceptable continous waveform.