ps2键盘检测（PS2 keyboard detection）.docVIP

ps2键盘检测（PS2 keyboard detection） PS/2 keyboard key detection Category: latest news release date: 2011-03-09 hits: 526 In the SCM system, often use the keyboard is a special keyboard, the keyboard are generally separate design, high cost, the use of hardware connection, and the reliability is not high, the situation in the application system that require keyboard more of the more prominent. Compared with this, PS/2 keyboard is widely used in PC system. It has the characteristics of low price, general reliability and less connection line (only using 2 signal lines), and can meet the requirements of many systems. Therefore, the application of PS/2 keyboard is a good choice in the SCM system. In this paper, PS/2 protocol and principle, read and identify the PS/2 keyboard, the first type of keyboard keys. 1 PS/2 protocol The PC is now widely used as the PS/2 interface for the mini - DIN 6 pin connector. Its pin is shown in figure 1. PS/2 equipment has master-slave, main equipment adopts female socket, male socket is adopted in equipment. The widely used PS/2 keyboard and mouse work from the device mode. The clock and data lines of the PS/2 interface are all collector An open circuit structure must be externally connected with a pull-up resistor. The general pull-up resistor is set in the main equipment. Data communication between master and slave devices is transmitted in a two-way synchronous serial mode, and the clock signal is generated from the device. (1) communication from equipment to main equipment When data is transmitted from the device to the main device, the clock line is first checked to verify that the clock line is high. If the level is high, data can be transmitted from the device; otherwise, the data can only be transmitted until the device has to wait for control of the bus. Each frame of the transmission consists of 11 bits, the timing of transmission and the meaning of each bit, as shown in figure 2. In each frame, the start bit is always 0, and the da