ModBus

Modbus is a Communication protocol used for networks of programmable automats. It functions on the main mode/slave. It consists of screen containing the address of the automat concerned, the function to be treated (writing, reading), the data and the code of checking of error called cyclic Check redundancy or CRC.

The protocol Modbus (registered trademark by Modicon) is a protocol of dialog based on a structure hierarchical between a main and several slaves.

Physical layer

The Modbus protocol can be implemented

  • On an asynchronous connection series of type RS-232, RS-422 or RS-485, with flows and at variable distances.

  • Via TCP/IP on Ethernet. One speaks then about Modbus TCP/IP .
  • Via Modbus More.

a connection multipoint of type RS-485 connects main and slaves via a differential pair which allows a high flow (up to 10 Méga-bits a second) at an important distance (until 1200m). It lays out of 2 noted polarized terminals of emission T (+), T (-) and of 2 noted polarized terminals of reception R (+), R (-).

See too

Internal bonds

External bonds

  • modbus.org
  • how the modbus functions
  • Simply Modbus - Master free and Slave software of demonstration which does not expire

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