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Author Topic: MB-Gateway automatic reads  (Read 3975 times)


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MB-Gateway automatic reads
« on: July 24, 2013, 02:09:21 PM »
After too much head scratching, and beating it on the table, (you may have seen my posts on other forums) I'm finally reading data from the Gateway automatic read registers. But my gateway does not always read the serial slave correctly!

My slave has a 10 charater text constant starting at MB holding register 3442. Using a direct ECRX read of the slave, I can read the characters into my PLC. If I use a separate Modbus application (MB TestPro), I can read the same data direct from the slave. When I turn on an automatic read of the data, it puts it in the correct Gateway registers, and I can read them into the PLC. HOWEVER, every so often I receive incorrect data. Instead of the text characters, I get garbage. Next scan, everything is OK. Turn off the auto read, things are normal. I have captured the bad data when using MB TestPro to read the data from the slave, so the problem is not in reading the Gateway.

Admittedly, I have a fair amount of traffic to the gateway and slave- two PLC/ECOM100, and a data logger, all reading the same registers in the slave. That's why I want the auto-read to function, it would unload the RS485 link substantially.

I have tried increasing the interpacket delay to 27ms. without success.

Any thoughts?

Edit 1- I was wrong, I still get occasional data errors- but many fewer- one per 15 minutes, vs. one a minute.
« Last Edit: July 24, 2013, 03:48:18 PM by bartb102 »

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