Since the inception of the IBM PC platform, the keyboard has served as
its primary input device and, along with the PC’s keyboard interface,
now serves as part of the PC architecture standard. However, in recent
years, PC hardware engineers have designed peripheral devices that
can be used in place of or in conjunction with the keyboard.
This application note discusses the hardware and software issues
involved in designing applications based on Motorola’s M68HC05
Family of microcontrollers that can interact with an IBM AT computer at
its keyboard interface. It explores using the interface as a power supply
and a low-speed serial data link between an MC68HC05-based
application and an IBM AT-compatible host computer. The major focus
is on applications that are capable of operating while the keyboard is
connected to the host PC.