A DESIGN OF A SIMPLE 8 BIT MICROPROCESSORS

Abstract

Internal circuit and design flow of microprocessor has not been well known by students.
The objective of this research is to show clearly how to design a simple microprocessor
that function work correctly. The method is designing a 16 bit simple microprocessor
using VHDL language. Design flow using Top Down approach. The method is used
because it can simulate and verified soon to know the unit works functionally without
designing the detail. The basic functional units of the processor are ALU, accumulator
and register set, control unit and busses. In order to processor can works properly, RAM,
Rom and I/O ports are added to the design. The processor comes with 16 basic
instruction that can be divided into three kinds of instruction as follows, ALU instruction,
data transfer, and branch instruction. Memory space of RAM is divided into three spaces
as follows, bit addressable, port, and space for data. The simulation and verification has
been done by Xilinx ISE program. The experiments results show the processor works for
arithmetic’s instructions in loop. Beside that the “Quiz Button” bit logics instruction that
used in digital control worked correctly for the processor. The microprocessor of this
research can be used for teaching students and for the basic microprocessor for the
further research to develop addition feature to the processor.