An 8-bit microcontroller made by Motorola.
Runs at speeds of up to 5Mhz, can have up to 768
bytes of RAM, 32kb of EPROM, 20kb of masked ROM
and 2kb of EEPROM on board.
Some variants also have on board A/D conversion.
IIRC, all 'HC11's have UARTs built in, and can communicate by a 3-wire serial interface.