Conerol Techniques To Modbus

Good Afternoon,

I am having a little problem with communications with a PLC Direct 205 (260 Processor) and a Uni Drive Sp using a Apps module and EZ-Motoin card. When I use the box instructions MRX & MWX I am using a shift register to cycle the read and writes A total of 10, so my shift register is from 2000 to 2017. I have noticed the read out on the drive to the parameters I am writing to breiely flash zero then load the value again some times, other times a zero is left until next scan. My scan time is 50ms or 100ms. Any ideas on what could be causing this? I have erased the program also used scratch pad. Not over writing from any other V-Memory location. Any ideas would be apperciated.

Tom

We have used Modbus to Control Techniques a lot, though I use stages to sequence through the MRX and MWX commands. Can you post your program (zip all the files together and post the zip file)? It is important that one command be finished (Buzy bit for the port is off) before starting the next communication command.

Hello Bernie.


Here is a smal part of the program. But with this only I still have the problem.

View attachment Demo Line 16.zip

Tom

Why don't you just change the 'Number of elements' in your first MWX to 'K12' and get rid of the other MWX's. Do all that in one communication. And you are reading back (MRX) a register you just wrote. I'm not sure I understand.

Thank You again for the quick reply Bernie.

I done as you said, wrote them with one instruction. My orginal program had them as one but when the drive display started flashing zero briefly, I split them up thinking it may help. but for some reason either with the new or old program the display is not flashing. Also the MRX was a typo.

Thanks for you time.

Tom