Download Woody overview

An Example Architecture
A Paper Computer - Woody
Woody's characteristics
Word size – 8 bits
One word
A Paper Computer - Woody
Woody's characteristics
Main
Memory
Word size – 8 bits
Memory size – 32 words
...
A Paper Computer - Woody
Woody's characteristics
Main
Memory
Word size – 8 bits
Memory size – 32 words
Memory addresses are 0
through 31 How many bits
does it take to represent
an address?
...
A Paper Computer - Woody
Woody's characteristics
Main
Memory
Word size – 8 bits
Memory size – 32 words
Memory addresses are 0
through 31. 3110 = 111112
...
A Paper Computer - Woody
Woody's characteristics
Word size – 8 bits
Memory size – 32 words
Memory addresses are 0
through 31. 3110 = 111112
Addresses can be
represented with 5 bits
Main
Memory
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
...
11110
11111
A Paper Computer - Woody
Woody's characteristics
Word size – 8 bits
Memory size – 32 words
Memory addresses are 0
through 31. 3110 = 111112
Addresses can be
represented with 5 bits
Woody uses signed
magnitude representation
for storing integers (no
floating point)
Main
Memory
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
...
11110
11111
Woody's CPU
Central Processing Unit
Instruction
Register
Program Counter
Register
Data Register
Instruction register – holds currently executing instruction from
program
Program Counter Register – hold address of next instruction to
execute
Data Register – holds the data used in the execution of an
instruction
Other Components
Input unit – device that allows the user to
enter values – e.g. keyboard
Output unit – device that allows Woody to
display a value (e.g. screen)
Woody's Assembly Language
Instruction
Argument
Meaning
CopyFrom
Location
Copy from Location to the Data Register
CopyTo
Location
Copy from Data Register to Location
Add
Location
Add the number at Location to the DR
Subtract
Location
Subtract the number at Location from the
DR
Read
Copy from the Input Unit to the Data
Register
Print
Copy from the Data Register to the Output
Unit
IfNegGoTo
Stop
Location
If the DR holds a negative value, go to
Location
Stop execution of the program
Machine Language
Instructions must be in binary form to
execute
Woody can't store "CopyFrom" nor
understand what to do with it
It is easiest if all instructions are the same
size and fit into a single word
How big can our instructions be?
Woody's Machine Language
Assembly
Language
Instruction
Machine
Language
Instruction
CopyFrom
000
CopyTo
001
Add
010
Subtract
011
Read
100
Print
101
IfNegGoTo
110
Stop
111