Register Addressing - ABB ACS880 Firmware Manual

686 Fieldbus control through the embedded fieldbus interface (EFB)
dedicated storage parameter (13.91 AO1 data storage and 13.92 AO2 data storage),
which are available in the source selection parameters 13.12 AO1 source and 13.22
AO2 source.
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Register addressing

The address field of Modbus requests for accessing holding registers is 16 bits. This
allows the Modbus protocol to support addressing of 65536 holding registers.
Historically, Modbus master devices used 5-digit decimal addresses from 40001 to
49999 to represent holding register addresses. The 5-digit decimal addressing limited
to 9999 the number of holding registers that could be addressed.
Modern Modbus master devices typically provide a means to access the full range of
65536 Modbus holding registers. One of these methods is to use 6-digit decimal
addresses from 400001 to 465536. This manual uses 6-digit decimal addressing to
represent Modbus holding register addresses.
Modbus master devices that are limited to the 5-digit decimal addressing may still
access registers 400001 to 409999 by using 5-digit decimal addresses 40001 to
49999. Registers 410000 to 465536 are inaccessible to these masters.
Note: Register addresses of 32-bit parameters cannot be accessed by using 5-digit
register numbers.