a-simple-8-bit-processor's Introduction

A-Simple-8-Bit-Processor

The objective of this project is to design a simple microprocessor with a custom instruction set. The processor should consist of the following four main components:

A register file
An Arithmetic and Logic Unit (ALU)
A Read-Only Instruction Memory (IMEM)
A Read/Write Data Memory (DMEM)

Instruction Set and Format

Your processor should implement the following basic instruction set:

Instruction	Opcode/Function	Operation
add rd, ra, rb	0000 / 000	rd = ra + rb
sub rd, ra, rb	0000 / 010	rd = ra - rb
and rd, ra, rb	0000 / 100	rd = ra AND rb
or rd, ra, rb	0000 / 101	rd = ra OR rb
addi rd, ra, imm	0100	rd = ra + imm
lw rd, imm(ra)	1011	rd = DMEM[ra + imm]
sw rd, imm(ra)	1111	DMEM[ra + imm] = rd
beq rd, ra, imm	1000	If(ra == rd) pc = pc + imm
j addr	0010	pc = pc + addr

The program code is stored as 16-bit instructions in the IMEM. The processor implements three types of instruction:

Type	15-12	11-9	8-6	5-3	2-0
R (Register)	Opcode	Rd	Ra	Rb	Func
I (Immediate)	Opcode	Rd	Ra	Imm[5:0]
J (Jumpp)	Opcode	Don’t care	Addr[7-0]

Data Path Components:

Program Counter: One 8-bit register
Register File: Holds 8-bit 8 register
Instruction Memory: 8-bit address input, and outputs 16-bit
Data Memory: 8-bit read/write memory
ALU: Performs arithmetic and logical operations

Control Unit: Generates necessary signals to the data-path. Check single-cycle ARM processor design in the lecture slides to design the signals and implement the control unit.

Hint: The signals can be defined as MemToReg, MemWrite, RegWrite, ALUSrc, Branch, Jump…

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