What is Modbus and What Modbus can do for us?

More and more industrial devices require Modbus nowadays. Then what is Modbus on earth and what Modbus can do for our applications? Here we have a short discussion for Modbus.    

What is Modbus?

Modbus is a communication protocol developed by Modicon systems. In simple terms, it is a method used for transmitting information over serial lines between electronic devices. The device requesting the information is called the Modbus Master and the devices supplying information are Modbus 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 Master can also write information to the Slaves. The official Modbus specification can be found at

What is it used for?

Modbus is an open protocol, meaning that it's free for manufacturers to build into their equipment without having to pay. It has become a very common protocol 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.

How does it work?

Modbus is transmitted over serial lines between devices. The simplest setup would be a single serial cable connecting the serial ports on two devices, a Master and a Slave.

The data is sent as series of ones and zeroes called bits. Each bit is sent as a voltage. Zeroes are sent as positive voltages and a ones as negative. The bits are sent very quickly. A typical transmission speed is 9600 baud (bits per second).

What is a Modbus Map?

A Modbus map is simply a list for an individual slave device that defines:

• what the data is (example, pressure or temperature readings)
• where the data is stored (which tables and data addresses)
• how the data is stored (data types, byte and word ordering)

Some devices are built with a fixed map that is defined by the manufacturer, while other devices allow the operator to configure or program a custom map.

Can a sim card router support Modbus?

The answer is yes. Now some sim card router already support Modbus to fit for market’s need. If you do not know how to choose, E-Lins Technology’s sim card router is a good choice for you. You have many products to choose, from 3g to 4g, from single sim to dual sim. For more details, why not freely contact with E-Lins Technology Co., Limited?