Modbus for Field Technicians

Please find the following documents which are helpful for Modbus

Art Science RS485 by BOB PERRIN

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Split from Modbus General Description.

Yes, the Chipkin Modbus note is excellent. 

The "Art and Science" article author is clearly conversant in troubleshooting transient issues, but his article involves field engineering at the extreme, it is not a general purpose 485 primer.

To qualify for a 485 primer one must provide the solution to the most common problem in 485 networking with devices from different vendors - which driver is the A driver and which is B driver?  Just because the lines are labeled A and B does NOT mean that field device labeling is the same as the chip labeling or that the labeling is not reversed or backwards from another vendor's labeling.

When 485 doesn't work, the first thing to do is to swap and the A and B lines to see if the labeling is reversed.   Swapped lines will not damage the drivers, but the drivers will not work.   That's the 101 course level take home for 485 networking.

K C Das

Please find the following documents which are helpful for Modbus

Art Science RS485 by BOB PERRIN

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Split from Modbus General Description.

 you really do a great job.the document is helpful,especial for freshman.

K C Das

Please find the following documents which are helpful for Modbus

Art Science RS485 by BOB PERRIN

------------------------------------------------------------------------------------------
Split from Modbus General Description.

Thanks. I found the Chickpin document very clarifying.

Kind regards,