since the first PLC since the first successful application in GM auto production line, PLC with its convenience, reliability and low price has been widely used.
But, after all, PLC is a black box, and can't control process real-time observed visually, compared with DCS are larger gap.
The development and popularization of computer technology, and provides a new technical means for PLC, can implement by computer monitoring and control process and results of PLC controller
, make the PLC.
But the PLC communication medium and different communication protocols, the following will introduce the main PLC communication medium, and the content of agreement.
1 U. S. manufacturer Rockwell AB Rockwell PLC is mainly including PLC2, PLC3, PLC5, SLC500 and ControlLogix model, PLC2 and PLC3 is early models, now with more small is SLC500 PLC controller
, medium is commonly ControlLogix, large with PLC5 series.
DF1 protocol is Rockwell communication protocol of each PLC
is supported by DF1 protocol can through a serial port, such as 232 or 422 medium for data transmission, also can through the DH, the DH +, DH485, ControlNet network media to transmit.
DF1 protocol specific content can be downloaded in the database of AB.
AB PLC also provides the OPC and DDE, contains in its integrated software
RSLogix DDE and OPC SERVER, you can through the software for data communications.
Of high-grade AB PLC also provides high-level language programming function, users can also through the programming to realize their own communication protocol.
GE GE now at home with more major is 90 -
30 series PLC, the two PLC is supported by SNP agreement, SNP agreement in the PLC manual there is the specific content of the agreement.
now GE PLC can also through the Ethernet link, GE's Ethernet protocol content is not made public, but GE provides a SDK development kit, communication can be based on the development kit.
2 European series Siemens Siemens series PLC mainly includes its early S5 and S7 - now
Early 400 various models such as PLC, S5PLC controller support is 3964 r protocol, but because now in domestic application is less, in addition to the extremely individual renovation project, there are few rather than for data communications.
200 is a small PLC
Siemens, because of its low price in the domestic large-scale applications, support the MPI, PPI and free communication port protocol.
PLC of Siemens 300 support for MPI, can also through the industrial Ethernet and PROFIBUS system and computer communications.
If you want to complete point-to-point communication, can use CP340/341.
S7400 as large PLC of Siemens, provides a complete function of communication.
Can communicate through MPI S7 standards, at the same time can through the C -
Bus, PROFIBUS and industrial Ethernet communication.
If you want to use a point-to-point communication, S7 -
400 need to through CP441 communication module.
Siemens communications protocol is not open, including many zijin bridge configuration software configuration software support the MPI, PPI, such as communications, usually by Siemens PROFIBUS and industrial Ethernet software for data communications.
schneider PLC type is more, also more in domestic application.
Its means of communication is primarily supported MODBUS and MODBUS PLUS two kinds of communication protocol.
MODBUS protocol has been widely used in industrial control industry, already is not just a PLC communication protocol, in the smart instrumentation, inverter and so on many smart devices have quite a wide range of applications.
MODBUS after further development, now has the MODBUS TCP way, through the Ethernet transmission in the form of communication is faster.
MODBUS PLUS relative to the MODBUS transmission faster and farther, the communication way need to install MODCON provide SA85 card in the computer and the need to install the card driver can communicate.
in addition to the above two ways, modicon PLC also supports such AS TCP/IP Ethernet, Unitelway, FIPWAY, FIPIO, the AS -
S and other communication methods.
3 series PLC omron series omron PLC is promotion in China.
In the mode of communication, OMRON now mainly adopts two kinds of communication methods: Host Link protocol is based on serial data transmission in the form of communication.
When the PLC into MONITOR mode, PC can and omron PLC communication.
Should pay attention to when and omron communication, communication between the two are for a certain period of time, if the communication too fast cause abnormal PLC communication.
ControlLink is a rapid communication way of omron PLC.
Control Link for data communication through the interface card, the card data exchange area between the two, by the board to realize data exchange to complete the data acquisition function.
Use this way communication must be configured omron driven.
Mitsubishi small PLC of mitsubishi PLC has a very wide range of applications in the country.
Mitsubishi PLC type is much also, mainly including FX series, series A and Q series.
Mitsubishi series PLC communication protocol is more, each series has its own communication protocol.
Such as FX series bd communications, including through programming the mouth or 232 through 485 bd way communication, etc.
The series A and Q series can be through the Ethernet communication.
Of course, mitsubishi PLC can also through the CC -
The LINK protocol communication.
panasonic panasonic between PLC and computer can communicate via a serial port and Ethernet.
Its use of communication protocol is MEWTOCOL agreement.
Like most Japanese PLC, MEWTOCOL protocol is simple.
Many, including zijin bridge configuration software, the software can directly read data from the PLC.
above the mainstream of the PLC is introduced. the device communications.
In addition to the above manufacturer, there are a lot of PLC manufacturer:
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