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RS 485 Modbus communication

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Thread Starter

Neeraj

How can device dependent operation (reading, writing) be performed on RS485 Modbus network, i.e. Modbus works in Register format?

What is the function code/sub-function code for device dependent operations (reading and writing)?
 
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Fred Loveless

The first byte in the Modbus protocol is the Device ID. If you set it to 0 then the message is a broadcast to all devices on the network. If you use a number other than 0 then only the device with that device ID responds to the packet, all other devices will ignore it.

Fred Loveless
Senior Application Engineer
Kepware Technologies
http://www.kepware.com
 
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