The COP421L is one model of a family of microcontrollers from National Semiconductor. It has 1K of 8-bit ROM and 64 4-bit nibbles of RAM. One game that used it is Milton Bradley Lightfight. It can be electronically dumped.
Milton Bradley LED game.
hardware description and pinout
Castle Toy Company game.
hardware description and pinout
Keyboard, mouse, RTC and power switch controller.
ROM array pic from Visual6502 with bits marked
