An Engineering Design of 4-bit Special Purpose Microprogrammed Processor

This work is a complementary part for what we proposed in [1], . In this paper, an undergraduate design experience for special purpose 4-bit microprocessor using the skills learned from digital logic design and Microprocessors courses is presented. The experience started in [1] by designing the ALU using the hardware printed circuit board and we are following it by completing the design by the instruction set architecture and the microprogram code. Our microprocessor contains – in addition to the ALU- six registers: A 4-bit accumulator register, Flag register that holds only zero (Z) and carry (C) flags, Program counter register (PC), Memory address register (MAR), Instruction register (IR), and Buffer Register. All programs and data are stored in the 1k RAM.