Re: Question about Modbus addressing

On 2007-04-26, Alexander Baranov <baranov@xxxxxxxxxxx> wrote:

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?

Probably the latter. Many control systems add an offset (such
as 30000) to the actal address as a way to indicate which
address space (which modbus command) is to be used to access
the desired object. For example 30100 might be float point
register address 100, while 20100 would be integer registers
address 100, and 10100 would bit input bit number 100.

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