ABB ACQ580 Firmware Manual page 374

370 Fieldbus control through the embedded fieldbus interface (EFB)
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 410000-465536 are inaccessible to these masters.
See parameter 58.33 Addressing mode.
Note: Register addresses of 32-bit parameters cannot be accessed by using 5-digit
register numbers.