I have a question which might be very simple to Modbus professionals:
Holding register (AO) is read/write. So, why do we even need input register (AI), discreate coil (DO) and contact (DI) ?
I imagine that 16 bit AI data can be stored in holding register as well and use code 3 to read. It seems input register is not quite needed.
Further more, DI and DO can be store in holding register as single bit. It just seems like holding register can do everything.
I must be wrong, please correct me and help me understand Modbus better.
Holding register (AO) is read/write. So, why do we even need input register (AI), discreate coil (DO) and contact (DI) ?
I imagine that 16 bit AI data can be stored in holding register as well and use code 3 to read. It seems input register is not quite needed.
Further more, DI and DO can be store in holding register as single bit. It just seems like holding register can do everything.
I must be wrong, please correct me and help me understand Modbus better.