The PPI of “PPI cable” in PLC can be understood as point-to-point. Point-to-point communication Point-to-Point Interface, communication supported by Siemens S7-200 CPU. Multi-master communication cable. Because the S7-200 CPU uses RS485, while the COM port of the PC uses RS232, the electrical specifications of the two are not compatible, and an intermediate circuit is required for matching. PC/PPI is actually an RS485/RS232 matching cable.
Multi-point communication MPI is often used in Siemens S7-300 CPU.
Siemens’ PPI (Point to Point) communication protocol adopts a master-slave communication method. The steps of a read and write operation include: first, the upper computer sends out a read and write command, the PLC responds correctly, and the upper computer sends a confirmation after receiving the response. Apply for the command, PLC completes the correct read and write response, and responds to the host computer data.
PPI is a protocol specially used for 200, USB is also a communication protocol, and RS485 is the physical layer definition of the interface. The USB/PPI cable is suitable for Siemens S7-200 series PLC, and it is a programming cable that provides serial connection, RS485 signal conversion, and PPI protocol conversion through the USB interface.
The Siemens PPI cable uses RS485, while the COM port of the PC uses RS232. The electrical specifications of the two are not compatible, and an intermediate circuit is required for matching. PC/PPI is actually an RS485/RS232 matching cable.
Please note that driver availability may vary depending on the specific model and brand of your USB PPI cable. Follow these general steps to find and download the driver:
you need to choose the right USB driver for the different versions. Economic version/upgrade version/isolated version use CH340 driver, High-speed communication version/Omnipotent version use FTDI driver.