Lab Assignment 2:MIPS single-cycle implementation

Electrical and Computer EngineeringUniversity of Cyprus

Lab Tutorial Assignment

• ISE Tool setup

• Any Questions?

• A solution/tutorial will be uploaded once all assignments have been submitted

The Five Classic Components of a Computer

• Datapath: The processor elements that operate on and/or store data• Control: The processor element that decides how and when parts of the

datapath are executed FSM

Processor

Control

Datapath

Memory

Input

Output

INTRODUCTION• The MIPS processor, designed in 1984 by

researchers at Stanford University.• Is a RISC (Reduced Instruction Set Computer)

processor. Compared with their CISC (Complex Instruction Set Computer) counterparts (such as the Intel Pentium processors), RISC processors typically support fewer and much simpler instructions.

• A RISC processor can be made much faster than a CISC processor because of its simpler design.

INTRODUCTION (…)

• RISC processors typically have a load-store architecture.

• Two instructions for accessing memory: – a load (l) instruction to load data from memory,– a store (s) instruction to write data to memory.

• None of the other instructions can access memory directly.

DataMemory(Dmem)

PC Registers ALUInstruction

Memory(Imem)

Stage 1 Stage 2 Stage 3 Stage 4

Stage 5

IFtch Dcd Exec Mem WBA

LU IM Reg DM Reg

5-Stage MIPS

STAGES OF EXECUTION IN MIPS5 stage instruction pipeline 1) I-fetch: Fetch Instruction, Increment PC2) Decode: Instruction, Read Registers3) Execute:

Mem-reference: Calculate Address R-format: Perform ALU Operation

4) Memory: Load: Read Data from Data Memory Store: Write Data to Data Memory

5) Write Back: Write Data to Register

Block Diagram of MIPS single-cycle processor

Datapath elements

• Instruction memory– PC register, adder increment PC by 4

• Register file• ALU• Data memory

Registers

Register #

Data

Register #

Datamemory

Address

Data

Register #

PC Instruction ALU

Instructionmemory

Address

Edge Triggered Methodology

• Unclocked vs. Clocked• Clocks used in synchronous logic

– when should an element that contains state be updated?— wouldn't want to read a signal at the same time it was

being written

cycle time

rising edge

falling edge

Edge Triggered Methodology Register file

• A clocking methodology defines when signals can be read and written

Clock cycle

Stateelement

1Combinational logic

Stateelement

2

Instruction Read From Memory Value Written to Register File

Write Data to Memory

Read Register ValuesExecute

The MIPS instructions format

Single-cycle Implementation

• All operations take the same amount of time - a single cycle

• long cycle time• Instructions same size• Source registers always in same place• Immediates same size, location• Operations always on registers/immediates

LAB2

• You will become familiar with the MIPS instruction set by implementing a single-cycle core in VHDL– The example code will be uploaded to the website

• You have two weeks for this project– don’t wait until the night before to tackle

LAB2

• You will be given the design skeleton of a single-cycle MIPS processor that is capable of performing some instructions.

• Complete the design of the single-cycle implementation in order to support the required MIPS instruction set.

MIPS 32 Instruction Set- We're ready to look at an implementation of the MIPS- Simplified to contain only:

- memory-reference instructions: lw, sw - arithmetic-logical instructions: add, sub, and, or, slt- control flow instructions: beq

- Generic Implementation:

- use the program counter (PC) to supply instruction address- get the instruction from memory- read registers- use the instruction to decide exactly what to do

EXECUTE

IFETCH

CONTROL

IDECODE

DMEMORY

IFETCH

IFETCH

MIPS

DEMO

• You'll want to build a suite of test programs to test the new capabilities of your implementation as you add them.– Test Programs are Stored in the IFETCH.vhd file

• You will be expected to run a number of supplied programs.

REPORT

• Objective of this lab and intro. • Your implementation• Your test programs and results (simulations) • Your conclusion • Attach your VHDL source code (email)

Important Announcements!

• Lab material (Tutorials, VHDL Files) will be uploaded in the website!

• Deadline for Lab 2 is on: 1/10/2014

• No Lab Lecture next week, but we can be at the lab if there are questions

Adding Instructions to MIPS(Tutorial)

• Branch not Equal (Bne)

• Load Upper Immediate (Lui)

Branch Not Equal (Ben)

Load Upper Immediate (Lui)