Modbus® Protocols

Modbus® protocols can be easily defined in their uses in both the industrial world and any industry or computer that uses communications to operate.  The protocol was developed in 1979 by Modicon and is used to establish communication between client and server (master/slave devices).Modbus® RTU (RS-232 or RS-485) is the most widely used protocol in industrial manufacturing because it is so easy to use and reliable.  It is commonly implemented within Industrial Automation Systems (IAS) as well as Building Management Systems (BMS).  Modbus® protocols can be used in multiple applications and devices, between sensors, devices and instruments and also for monitoring purposes.

Modbus® RTU works well when the application requires wireless communication.  Therefore, many oil/gas and substation applications use this protocol for operation.  Other industry types that may use Modbus® protocols include energy applications, transportation, infrastructure and building.

Simplicity is the Key

Modbus® RTU protocols have one key feature that has resulted in their widespread acceptance, and that’s simplicity.  The protocols use a simple message transmission system (Master/Slave communication) between devices, which makes it easy to apply them to queues, tables, etc.  Basically, a request is initiated from the Master (client) and then transmitted to the Slave (server) to be carried out.  The server is informed by a function code field.  A response is then sent back to the master indicated the command was received.

There may also be multiple actions required of the server.  In this instance, sub-function codes may be added to the functions.

When compared with some of the newer protocols on the market, Modbus® protocols are simple in design and easier to implement.  Modbus® RTU modules require less memory as well, meaning less space is needed to implement Modbus® RTU on a PIC processor or CPU.

Modbus® ProtocolsModbus® Protocol – MicroManager – by Carotron

Check out Carotron’s latest Micromanager 3010 Series, a MicroManager, particularly the Modbus(R) RTU I/O expansion module MM3010-MBS.  These Modbus® protocols can be used in industrial SCADA applications and provides analog and digital I/O plus frequency inputs.  And combined with an HMI Touchscreen, it can be used as a simple, yet powerful logging and data acquisition system.  See the brochure, instruction manual and other information on the main product page.

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