Introduction to Computer Engineering.pdf

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Introduction to Computer
Engineering
CS/ECE 252, Fall 2012
Prof. Guri Sohi
Computer Sciences Department
University of Wisconsin – Madison
Chapter 3
Digital Logic
Structures
Slides based on set prepared by
Gregory T. Byrd, North Carolina State University
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Transistor: Building Block of Computers
Microprocessors contain millions of transistors
• Intel Pentium II:
7 million
• Compaq Alpha 21264:
15 million
• Intel Pentium III:
28 million
Logically, each transistor acts as a switch
Combined to implement logic functions
•
AND, OR, NOT
Combined to build higher-level structures
•
Adder, multiplexer, decoder, register, …
Combined to build processor
•
LC-3
3-3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Simple Switch Circuit
Switch
open:
•
No current through circuit
•
Light is
off
•
V
out
is
+2.9V
Switch
closed:
•
•
•
•
Short circuit across switch
Current flows
Light is
on
V
out
is
0V
Switch-based circuits
can easily represent two states:
on/off, open/closed, voltage/no voltage.
3-4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
N-type MOS Transistor
MOS = Metal Oxide Semiconductor
•
two types: N-type and P-type
N-type
•
when Gate has
positive
voltage,
short circuit between #1 and #2
(switch
closed)
•
when Gate has
zero
voltage,
open circuit between #1 and #2
(switch
open)
Gate = 1
Gate = 0
Terminal #2 must be
connected to GND (0V).
3-5

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