Re: Question about Modbus addressing

Alexander Baranov wrote:
Hello everybody.
I have a specification of a certain device, in which a set of Modbus input registers have addresses from e.g. 30100 to 30200. Does it mean that I have to put these address values directly to my request packet or I have to subtract 30000 and turn them to 100 - 200?
I could not find any instruction of that kind in Modbus protocol specification.
Regards and thanks
Alex

These addresses, although still valid are from past times. In the old MODBUS specification (MODBUS Over Serial Line FOR LEGACY APPLICATIONS ONLY) you will see that these are typically used for input registers (3X references). See p39 for this in the document PI_MBUS_300.pdf available at http://www.modbus.org.

Regards,
Christian

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