Each block of 4 bits is represented by one of the sixteen characters from 0 to F. Long strings of ones and zeroes are difficult to read, so the bits are combined and shown in hexadecimal. When troubleshooting problems, it can be helpful to see the actual raw data being transmitted. A typical transmission speed is 9600 baud (bits per second). Zeroes are sent as positive voltages and a ones as negative.

The data is sent as series of ones and zeroes called bits. The simplest setup would be a single serial cable connecting the serial ports on two devices, a Master and a Slave. Modbus is transmitted over serial lines between devices. Versions of the Modbus protocol exist for serial lines (Modbus RTU and Modbus ASCII) and for Ethernet (Modbus TCP). Modbus is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems. It is used widely by many manufacturers throughout many industries.Modbus is typically used to transmit signals from instrumentation and control devices back to a main controller or data gathering system, for example a system that measures temperature and humidity and communicates the results to a computer. It has become a standard communications protocol in industry, and is now the most commonly available means of connecting industrial electronic devices. Modbus is an open protocol, meaning that it's free for manufacturers to build into their equipment without having to pay royalties. The official Modbus specification can be found at The M aster can also write information to the Slaves. In a standard Modbus network, there is one Master and up to 247 Slaves, each with a unique Slave Address from 1 to 247.

The device requesting the information is called the Modbus Master and the devices supplying information are Modbus Slaves.

In simple terms, it is a method used for transmitting information over serial lines between electronic d evices. Modbus is a serial communication protocol developed by Modicon published by Modicon® in 1979 for use with its programmable logic controllers (PLCs). This document describes how modbus works and what needs to be done for proper installation.

Modbus rtu serial communication protoco