basics of the instruction set architecture

8/7/2019 Basics of the Instruction Set Architecture

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BasicsInstruction Set Architecture

Panickos Neophytou

Recitation 1 09/07/2005

09/12/2005

CS0447: Computer Organization and

Assembly

Link for this presentation:

www.cs.pitt.edu/~panickos/classes/cs0447/Basics.ppt


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Contact info

Panickos Neophytou

Office 6514 Sennott Square Office Hours: Monday 2:30-5:30 & Tuesday 3:45-6:45

Email [email protected] (use cs0447 anywhere in the

subject to get my attention) TAs course web page

www.cs.pitt.edu/~panickos/classes/cs0447 (underconstruction BUT available)


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Outline

Decimal to Binary conversions

Binary to Hexadecimal conversions Instruction Set Architecture

SPIM


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Example 1 - (Convert Decimal 44 to Binary)


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Binary to Hexadecimal conversions

In the Hexadecimal

system you have 16symbols to representnatural numbers.

Dec. Hex Dec. Hex

0 0 8 81 1 9 9

2 2 10 A

3 3 11 B

4 4 12 C

5 5 13 D

6 6 14 E

7 7 15 F


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Binary to Hexadecimal conversions

Convert the following Hex number to Binary:

286F A3E1

Convert the following Binary number to

Hexadecimal: 0101 0011 1111 0110 1011 1010 0001 1100


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Instruction Set Architecture

op Operation code

rs First source register operand

rt Second source register operand

rd Destination register operand

shamt Shift amount - used in shift instructions

funct Select the variant of the operation in the op code field

op rs rt rd shamt funct

6 bits 5 bits 5 bits 5 bits 5 bits 6 bits


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Specific Instruction Formats

Format 6 bits 5 bits 5 bits 5 bits 5 bits 6 bits Comments

R op rs rt rd shamt funct Arithmetic

I op rs rt address/immediateTransfer,

branch,immediate

J op target address Jump


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Arithmetic Instructions

Instruction Example Meaning Comments

add add $1,$2,$3 $1=$2+$3 Always 3 operands

subtract sub $1,$2,$3 $1=$2-$3 Always 3 operands

add immediate addi $1,$2,10 $1=$2+10 add constant

add unsigned addu $1,$2,$3 $1=$2+$3 Always 3 operations

subtract unsigned subu $1,$2,$3 $1=$2-$3 Always 3 operations

add immed.unsigned addiu $1,$2,10 $1=$2+10 Always 3 operations


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Logical


and and $1,$2,$3 $1=$2&$3 3 register operands

or or $1,$2,$3 $1=$2|$3 3 register operands

and immediate andi $1,$2,10 $1=$2&10 AND constant

or immediate or $1,$2,10 $1=$2|10 OR constant

shift left logical sll $1,$2,10 $1=$210 Shift right by constant


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Data Transfer


load word lw $1,10($2) $1=Memory[$2+10] memory to register

store word sw $1,10($2) Memory[$2+10]=$1 register to memory

load upperimmed.

lui $1,10 $1=10x2^16load constant into upper16 bits


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Conditional Branch


branch on equal beq $1,$2,10if($1==$2)go toPC+4+10

Equal test

branch on notequal bne $1,$2,10

if($1!=$2)go toPC+4+10 Not equal test

set on less then slt $1,$2,$3if($2


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Unconditional Jump


jump j 1000 go to 1000 Jump to target address

jump register jr $31 go to $31 For switch, procedure return

jump and link jal 1000 $31=PC+4;go to 1000 For procedure call


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SPIM

Spim is a self-contained simulator that will

run MIPS32 assembly language programs. Freeware

Can be downloaded and installed ontoWindows or Unix based machines from:

http://www.cs.wisc.edu/~larus/spim.html

Will be used for assignments


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SPIM

Registers

Instructions

LoadedData

Output


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SPIM -Assembler Syntax

Program includes .data and .text

Comments begin with #. Rest of line is ignored.

Identifier names are sequence of letters, numbers, underbars (_) and dots (.).

Labels are declared by putting them at beginning of line followed by colon. Uselabels for variables and code locations.

Instruction format: op field followed by one or more operands: addi $t0, $t0, 1

Operands may be literal values or registers.

Register is hardware primitive, can stored 32-bit value: $s0

Numbers are base 10 by default. 0x prefix indicates hexadecimal.

Strings are enclosed in quotes. May include \n=newline or \t=tab. Used for prompts.


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SPIM

Simple Example:

# SPIM Code to print hello world# a comment starts with a till the end of the line

.data # start putting stuff in the data segment

greet: .asciiz Hello world\n # declare greet to be the string

.text # start putting stuff in the text segment

main: # main is a label here. Names a function

li $v0, 4 # system call code for print_str

la $a0, greet # address of string to printsyscall # print the stringjr $ra # return from main

# here li is load immediate into an integer register

# la is load computed address into an integer register

# jr is standard return from function call...$ra contains return address


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SPIM

Modify the program by adding these

instructions: addi $10, $10, 4

addi $11, $11, 28

add $12, $10, $11

Use the step option (from the Simulatormenu) of SPIM to watch your programsexecution step-by-step.


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MIPS Basics

Implementing Conditional Statements

if ( i == j )

i++;

j--;

bne $r1, $r2, L1 # branch if ! ( i == j )

addi $r1, $r1, 1 # i++

L1: addi $r2, $r2, -1 # j--

if ( i == j )

i++;

elsej--;

j += i ;

bne $r1, $r2, ELSE #branch if !( i == j )

addi $r1, $r1, 1 # i++

j L1 # jump over elseELSE: addi $r2, $r2, -1 # j

L1: add $r2, $r2, $r1 # j += i

basics of the instruction set architecture

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