For low-cost small systems, especially single-board microcomputers and
microprocessor-based instruments,the front panel (or console) is often
implemented by using simple keyboard and display units as input and output
devices.
9-4-1 Keyboard Design
Unlike a terminal, mechanical contact keyboard, for which the key switches
are organized in a matrix form, does not include any electronics.Figure 9-30
illustrates how a 64-key keyboard can be interfaced to a microcomputer
through two parallel I/O ports such as those provided by an 8255A.
