Promotic
WikipediaLinkedInYoutubeTwitterFacebook

Communication by Modbus protocol

Types of Modbus communication protocols:
1. Modbus RTU - serial binary protocol of the Master/Slave type
2. Modbus ASCII - serial ASCII protocol of the Master/Slave type
3. Modbus TCP/IP - classic Ethernet TCP/IP with the 10/100 Mbit/s speed rate.
4. JBUS - limited set of communication messages of the Modbus RTU type
5. MODBUS PLUS - deterministic token LAN, peer-to-peer protocol, 1Mbit/s.
 
All protocols have common services and functions (e.g. 03-Read Holding Registers (Read Output Registers), etc.), they make use of another communication frame with various methods of addressing individual devices.
 
The Modbus communication protocol can be used for the following devices:
Modicon, Telemecanique, ABB AC31, Honeywell, Beckhoff, ADAM, Hypel, Tronic Control, heat meters etc.
 

1. Modbus TCP/IP

It is a network protocol - classic Ethernet TCP/IP with the 10/100 Mbit/s speed rate (standard net HW Ethernet card is sufficient). The communication principle (1Master x nSlave) is the same as for Modbus RTU.

For this communication in the PROMOTIC system can be used: PmModbusMr - Driver for communication by Modbus Master protocol.

 
The data transfer into the PROMOTIC system can be also implemented over the communication OPC server that is supplied, for example, by the Schneider Electric company. Note: The Schneider Electric company supplies also HW converters (bridges) with various conversions: MB/MB+, MB/Ethernet, MB+/Ethernet (all are functional in both transfer directions).

2. Modbus RTU

The serial binary communication protocol. It is the communication standard that became widely used and all series of PLC's and other device producers support it. It goes about the network protocol of the 1Master x nSlave type. The Slave devices can be 254 at the most.

For this communication in the PROMOTIC system can be used:

3. Modbus ASCII

The serial ASCII communication protocol. The protocol is similar to Modbus RTU, but the binary content is transformed to common ASCII characters. It is not used as frequently as Modbus RTU.

For this communication in the PROMOTIC system can be used:

4. JBUS

The serial JBUS protocol is the subset of the Modbus RTU protocol communication messages that makes use mostly the Modbus protocol messages for reading/writing data (messages of 1-8,11-12,15-17 types are supported). The number of Slave stations is limited to 32 at the most. The Modbus communication drivers in the PROMOTIC system promote all messages of the JBUS protocol.

5. MODBUS PLUS

It goes about the communication network protocol (deterministic token LAN). All stations are equivalent on the network (peer-to-peer access). The ModbusPlus supports on the network 64 stations at the most and transfers data between them by the 1Mbit/sec speed rate.

For the communication with the ModbusPlus protocol it is necessary to accommodate the PC station by the special HW network card (e.g. from the Schneider Electric company). The data transfer into the PROMOTIC system can be implemented over the communication OPC server that is supplied also by the Schneider Electric company.

© MICROSYS, spol. s r. o.Tavičská 845/21 703 00 Ostrava-Vítkovice