Interfacing to the PS/2 Keyboard and Mouse

Chapter 11 describes the PS/2 keyboard and mouse operation and presents interface examples for integrating designs on an FPGA board. Keyboard scan code tables, mouse data packets, commands, status codes, and the serial communications protocol are included. VHDL code for a keyboard and mouse interface is also presented.

The PS/2 interface was originally developed for the IBM PC/AT’s mouse and keyboard in 1984. The Altera FPGA boards support the use of either a mouse or keyboard using a PS/2 connector on the board (not both at the same time). This provides only the basic electrical connections from the PS/2 cable and the FPGA chip. It is necessary to design a hardware interface using logic in the FPGA chip to communicate with a keyboard or a mouse. Serial-to-parallel conversion using a shift register is required in the interface hardware.