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Unread October 10th, 2019, 06:55 AM   #1
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johnnyboy1852000 is offline
Join Date: Apr 2017
Location: Watertown
Posts: 2
Modbus RTU Issues

Hi Everyone,

I seem to be having issues communicating through Modbus RTU from my Horner XL7e to my Emerson Drives. The Connection is there but the drives are supper slow to respond.

Seems to me like a conflict somewhere but, I can not seem to find what's holding me up. At first I thought it was a bad port on the PLC because I stole a PLC that runs the same program from a currently running machine and everything works fine. So I ordered a new touchscreen and the same thing is happening SLOW responses from the drives.

any help or suggestions would be greatly appreciated.
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Unread October 10th, 2019, 08:52 AM   #2

gclshortt is offline
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Join Date: Dec 2014
Location: Cobourg
Posts: 2,900
The above thread will show the XL4 communicating to a Solo process controller via Modbus RTU (RS485)

A couple of things to check.
- RS485 termination resistor
- Ensure all of the parameters like parity, bit rate, stop bits are the same on all of the devices.
- Increase the baud rate to see if speeds improve.

On the Horner a status register can be programmed into the communications. Does it contain any information?

Just a couple of thoughts.
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Unread October 11th, 2019, 04:46 PM   #3
Gene Bond
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Gene Bond is offline
Join Date: May 2004
Location: Indianapolis, IN
Posts: 363
For speed considerations, I map my registers into Menu 0. I usually have 0.060 through 0.063 for my writes (to the drive), and 0.064 to 0.070 for my reads (to the plc).

Also, are you using the CT RTU driver? It's on the Horner web site. Seems to work better than the generic Modbus.
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