ModMaster Manual v3.16 - 1.1. Overview
ModMaster is a versatile Modbus diagnostic program that can be used to test almost any device or system that uses the Modbus protocol.
ModMaster is a Modbus master that provides two ways of sending commands to a Modbus slave:
You can define some Modbus registers and use the Read, Write and Poll buttons to send requests to the slave. See Setup for using defined registers for how to do this.
Alternatively, you can define and send Modbus commands using the Define Command page - this method does not use register definitions. See Setup for sending commands only for how to do this.