What are the network communication protocols of Siemens S7-200PLC? What are the characteristics of each?

The protocols include the following:

1.PPI protocol:

PPI communication protocol is a communication protocol specially developed by Siemens for the S7-200 series PLC. Built into the S7-200CPU. The PPI protocol is physically based on the RS-485 port, and PPI communication can be achieved through shielded twisted pairs. The PPI protocol is a master-slave protocol. The master station device sends a request to the slave station device, and the slave station device responds. The slave station cannot actively send information. The master station communicates with the slave station through a shared connection managed by the PPI protocol.

Features:

PPI protocol does not limit the number of master stations communicating with any slave station, but in a network, the number of master stations cannot exceed 32. The most basic purpose of the PPI protocol is to allow the Siemens STEP7-Micro/WIN programming software to upload and download programs and the Siemens human-machine interface to communicate with the PC.

2.MPI protocol:

MPI protocol, its full English name is Multi-point-Interface. Master/master protocol or master/slave protocol can be configured between PLCs. How to operate depends on the device type: If the control stations are all s7-300/400 series PLCs, then establish a master/master connection relationship. Because the MPI protocol supports multi-master station communication, all s7-300CPUs can be configured as network master stations. , data exchange between PLCs can be realized through the master/master protocol. If some control stations are s7-200 series PLCs, a master/slave connection relationship can be established. Because the s7-200CPU is a slave station, the user can realize the data reading and writing operations of the s7-300CPU on the s7200CPU through network instructions.

3. Freeport communication

Freeport communication means that the PLC provides serial communication hardware and related instructions for customizing the communication protocol. In the control system, when it is necessary When the communication protocol of the control device connected to the PLC is known, the communication protocol can be programmed in the PLC to communicate data with the control device. Visual Basic is used for programming in the computer, thereby realizing direct control of the computer and the programmable controller.

Features:

It has the characteristics of high efficiency, easy implementation, simple communication hardware, and easy configuration, and is widely used in the field of industrial control.

4. PROFIBUS-DP protocol:

The master station periodically reads the input information of the slave station and periodically sends the output information to the slave station. The bus cycle time must be shorter than the master station (PLC) program cycle time. In addition to periodic user data transmission, PROFIBUS-Dp also provides aperiodic communication required by intelligent devices for configuration. Diagnostics and alarm handling.

Features:

Rate: In a distributed system with 32 sites, PROFIBUS-DP transmits 512bit/s input and 512bit/s output to all sites, at 12Mbit/s It only takes 1 millisecond.

Diagnostic function: The expanded PROFIBUS-DP diagnostics can quickly locate faults. Diagnostic information is transmitted on the bus and collected by the master station.