Modbus Newbie Question


Thread Starter


I want to implement modbus on devices, however I don't know the definition of discrete input, input register, holding register, coil.

Also, do i need to implement all those function to read/write these values?

MY own interpretation is that: 1) input: device hardware input, 2) Coil: Hardware Output 3) holding register: status of the device. Am I right?
You're very close, 1) input: device hardware discrete input, 2) Coil: Hardware discrete Output
3) holding register: is a read or write register (function code 3 or 16), like an analog value. A holding register is a single 16 bit register. It can be read as signed or unsigned, decimal, BCD, double integer or float. The latter 2 require two consecutive holding registers (4XXXX). There are also input registers (3XXXX), which are analog type read only.

Hope this helps!