ModMaster Manual v3.15 - 2.3.2. Defining address ranges
The page enables you to set up the mapping between message addresses and model addresses.
For each address range, you have to specify a "base address" and a "number of addresses".
The number of addresses is simply the number of message addresses in the range, i.e. for each message address:
message_address >= 0 and message_address < number_of_addresses
The base address is the model address that corresponds to message address 0. For holding registers and input registers this means that for each model address:
model_address = base_address + message_address
This also applies to coils and discrete-inputs, provided that you use 1-bit "discrete" registers. If the coil or discrete input address range does not overlay the holding register or input register address range, then it is simplest to use 1-bit registers for coils and discrete inputs.