I've been asked to write new programming for
signal routing system using the Atmel AT89C51 in place of the Motorola MC68HC705P3S used in their
current routers. This change is for several reasons, not the least is component count and cost.
Today an MC68HC705P3s costs $15.95 (from Jameco), has to
emulate a UART and, therefore, uses up all its interrupts and needs hardware to interface to an XT
keyboard. The Atmel flash AT89C51 costs only $3.49 (from JDR),
has an onboard UART, and can talk to the more modern AT keyboards with ease.