What are Holding Registers and Input Registers in Modbus?
“Holding Registers” and “Input Registers” are two different kinds of registers in a slave device that are used in Modbus communication, and each has a specialized function:
Holding Registers:
A Modbus master can use these registers for both reading and writing since they are read-write registers. Configuration information, setpoints, and other values that must be changed or managed by the master device are frequently stored in holding registers. The Modbus function codes 03 (Read Holding Registers) and 06 (Preset Single Register) are frequently used with holding registers for reading and writing, respectively.
input registers:
Read-only registers known as input registers are made to hold data that the slave device provides to the Modbus master without permitting changes. Process values or sensor readings that the master device can only read are usually stored in input registers. To retrieve data from input registers, utilize function code 04 (Read Input Registers).