Design Recipes for FPGAs: Using Verilog and VHDL

12

PS/2 Keyboard Interface

Introduction

The PS/2 keyboard is a standard interface to both computers and

also many Field Programmable Array (FPGA) development kits.

The protocol is a serial one and in this chapter the basics of the

protocol will be reviewed and also a simple VHDL interface code

to enable the designer to use a PS/2 keyboard, primarily on a stan-

dard FPGA development kit.

PS/2 keyboard basics

The origins of the PS/2 keyboard are back in the 1980s with the pro-

liferation of the IBM Personal Computer (PC). This had the generic

name of a ‘Personal System’ – hence PS and the second version of

this was therefore called the PS/2 – and the interface technology has

remained under that name ever since. The keyboard interface evolved

from the XT (83 ...