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EENG 2710 Chapter 0

Introduction

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Chapter 0 Homework

None

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Computer Generations

• 1940’s - Early 1950’s– Labeled first generation– Vacuum tube computers

• Late 1950’s – Second generation– Transistor computers

• 1960’s – Early 1970’s– Third generation– Integrated Circuit computers

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Computer Generations

• Late 1970’s – 1980’s– Fourth generation– Very large scale integration (VLSI) computers

• Now– Fifth generation ?

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Evolution of Intel Computers

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Analog vs. Digital• Analog:

– A way of representing a physical quantity by a proportional continuous voltage or current.

• Digital:– A way of representing a physical quantity in

discrete voltage steps.

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Analog Electronics

• Values are continuously variable between defined values.

• Can have any value within a defined range.

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Analog Electronics

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Periodic Digital Waveforms

• A periodic digital waveform is a time-varying sequence of logic HIGHs and LOWs that repeat over some period of time.

• Period (T) is the time required for the pattern to repeat.

• Frequency (f) is the number of times per second a signal repeats and is the reciprocal of period.

• f = 1/T

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Periodic Digital Waveforms

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Aperiodic Digital Waveforms

• An aperiodic digital waveform is a time-varying sequence of logic HIGHs and LOWs that does not repeat.

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Aperiodic Digital Waveforms

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Waveform Definitions

• Time HIGH (th) is the time a logic signal is in its HIGH state.

• Time LOW (tl) is the time a logic signal is in its LOW state.

• Duty cycle is the ratio of the time a logic signal is HIGH (th) to the period (T).

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Duty Cycle

thtl

T

Duty Cycle = th/T

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Pulse Waveforms

• A pulse is a momentary variation of voltage from one logic level to the opposite level and back again.

• Amplitude is the voltage magnitude of a pulse.

• Edge is the part of a pulse representing the transition from one logic level to the other.

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Pulse Waveforms

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Pulse Waveform Characteristics

• Rising edge is the transition from LOW to HIGH.

• Falling edge is the transition from HIGH to LOW.

• Leading edge is the earliest transition.

• Falling edge is the latest transition.

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Pulse Waveform Characteristics

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Pulse Waveform Timing

• Pulse width (tw) is the time from the 50% point of the leading edge to the 50% point of the trailing edge.

• Rise time is the time from 10% to 90% amplitude of the rising edge.

• Fall time is the time from 90% to 10% amplitude of the falling edge.

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Pulse Waveform Timing

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Transition of Computer Programs Into Machine Language

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Digital Electronics

• Values can vary only by distinct, or discrete, steps.

• Can only have two values.

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Digital Logic Levels

• Logic HIGH is the higher voltage and represented by binary digit ‘1’.

• Logic LOW is the lower voltage and represented by binary digit ‘0’.

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Digital Logic Levels

0.8 V

3.5 V

5 V