TB840A  PLC communication method analysis

1. RS485 serial port communication

TB840A  Third-party devices are mostly supported, and the Siemens S7 PLC can control serial communication by selecting a free port communication mode. In the simplest case, only send instructions (XMT) to send information to a third-party device such as a printer or inverter. In any case, it must be programmed through S7 PLC.
When the free port mode is selected, the user can control the operation of the communication port by sending instructions (XMT), receiving instructions (RCV), sending interrupts, and receiving interrupts.
2. PPI communication
TB840A The PPI protocol is the most basic communication mode of the S7-200CPU, which can be realized through the original port (PORT0 or PORT1), and is the default communication mode of the S7-200CPU.
PPI is a type of master-slave protocol communication where the master-slave station is in a token ring network. The user can read and write network instructions in the CPU, that is, the network read and write instructions are run on the PPI protocol. Therefore, PPI can only write programs on the master side, and it is meaningless to read and write instructions on the network of the slave station.

3. TB840AMPI communication
MPI is a simple communication mode. The communication rate of the MPI network is 19.2Kbit/s to 12Mbit/s. The MPI network supports a maximum of 32 nodes and the maximum communication distance is 50M. The communication distance is long, and the communication distance can be extended through the repeater, but the repeater also occupies the node.
MPI network nodes can usually be attached to S7-200, man-machine interface, programming equipment, intelligent ET200S and RS485 Repeaters and other network components.
MPI communication between Siemens PLC and PLC generally has 3 communication methods:
1) Global packet communication
2) No configuration connection communication mode
3) TB840A Configuration connection communication mode
4. PROFIBUS-DP communication
PROFIBUS-DP Fieldbus is an open fieldbus system that complies with European and international standards. The structure of PROFIBUS-DP communication is very compact, the transmission speed is very high and stable, which is ideal for the communication between the PLC and the field scattered I/O equipment.
5. TB840A Ethernet communication
The core idea of Ethernet is the use of shared public transport channels, an idea that originated at the University of Shawell in 1968. In 1972, Metcalfe and David Boggs (both well-known network experts) set up a network that connected different ALTO computers together, as well as the EARS laser printer.