Modbus Holding Register Address

Ignition
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2

Whose Modbus Spec? The official Modbus Specification disagrees with whatever you are looking at.

And device makers don't have to implement everything, so device-specific address ranges abound.

It seems to me you are stumbling on the "area prefix" the Modbus Spec calls out for various types of data. To summarize:

  • Area zero: Output coils and other writable booleans. Classic address range 00001 through 09999, expanded to 000001 through 065536, on the wire with function codes 0x01 and 0x05 and 0x0f as 0x0000 through 0xffff. In Ignition as Cn, where n is 1-65536 or 0-65535 depending on your zero-based-addressing setting.

  • Area one: Discrete inputs or other readonly booleans. Classic address range 10001 through 19999, expanded to 100001 through 165536, on the wire with function code 0x02 as 0x0000 through 0xffff. In Ignition as DIn, where n is 1-65536 or 0-65535 depending on your zero-based-addressing setting.

  • Area three: Analog input registers and other readonly short integers. Classic address range 30001 through 39999, expanded to 300001 through 365536, on the wire with function code 0x04 as 0x0000 through 0xffff. In Ignition as IRn, where n is 1-65536 or 0-65535 depending on your zero-based-addressing setting.

  • Area four: Holding registers and other writable short integers. Classic address range 40001 through 49999, expanded to 400001 through 465536, on the wire with function code 0x03 and 0x06 and 0x10 and 0x16 as 0x0000 through 0xffff. In Ignition as HRn, where n is 1-65536 or 0-65535 depending on your zero-based-addressing setting.

Any of the "classic" or "expanded" formats need to have their prefix digit stripped off before using with Ignition's character-based prefixes. You kind of have to read the device maker's programmers' minds sometimes, but when hexadecimal is shown for an address, it almost always means the zero-based offset intended for use "on the wire". And most commonly means it is a holding register.

Your device should have more information, possibly scattered or in examples, to help you decipher what they've done.

There's also an area six, "File Records", that isn't supported by Ignition's native driver. See my alternate driver if you need that: