Chapter 1 : Introductory Digital Concepts

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Chapter 1 Introductory Digital Concepts

• 1.1 Digital and Analog Quantities
• 1.2 Binary Digits, Logic Levels and Digital
  Waveform
• 1.3 Introduction to Logic Operations
• 1.4 Overview of Logic Functions
• 1.5 Fixed-Function IC
• 1.6 Programmable Logic Devices (PLD)

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• 1.1 Digital and Analog Quantities
• 1.2 Binary Digits, Logic Levels and Digital
  Waveform
• 1.3 Introduction to Logic Operations
• 1.4 Overview of Logic Functions
• 1.5 Fixed-Function IC
• 1.6 Programmable Logic Devices (PLD)

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1.1 Digital and Analog Quantities
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Definition Analog Digital

• Analog?
• Varies over a continuous range of values
• Examples of analog quantities time, pressure,
  sound.

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• Digital?
• A discrete set of values.
• Varies in discrete (separate) steps.

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Analog vs Digital

• Analog
• Use base 10 (decimal)
• Represented by 10 different level
  0,1,2,3,4,5,6,7,8,9
• Analog system A combination of devices that
  manipulate values represented in analog form

• Digital
• Use base 2 (binary)
• Represented by 2 different level 0 and 1 or low
  and high.
• Digital system A combination of devices that
  manipulate values represented in digital form.

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The Digital Advantages

• Ease of design, Ease of storage,
• Accuracy and precision are easier to maintain,
  Programmable operation, Less affected by noise,
  Ease of fabrication on IC chips
• Thus, the systems is more efficient and reliable
• ?? - Data Processing
• ?? - Data Transmission
• ?? - Data Storage

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A System Using Digital and Analog Methods
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1.2 Binary Digits, Logic Levels and Digital
Waveform
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Logic Levels
5.0V
In TTL Bit 1 2 5V(high) Bit 0 0
0.8V(low) Undefined 0.8 2V
2.0V
0.8V
0V
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Binary Digits and Digital Waveforms
Positive Logic (active high) HIGH 1 (Bit
1) Low 0 (Bit 0)
Negative logic (active low) High 0 Low 1
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Frequency (f) vs. Period (T)

• Frequency (f) the rate at which the pulse
  waveform repeats itself. Measured in cycles per
  second or Hertz (Hz)
• Period (T) the time from the edge of one pulse
  to the corresponding edge of the next pulse.
  Measured in seconds
• f 1/T
• T 1/f
• Example clock frequency f 100Hz,
• so, period,T 1/100Hz 1010-3s
• ?1010-310310ms

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Unit Conversion
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Pulse Width

• Pulse width (tW) A measure of the duration of
  the pulse.

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Duty Cycle
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Example a periodic digital waveform has a pulse
width 1ms and period time 10ms, calculate duty
cycle? Duty cycle 1ms/10ms 100 10
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Timing Diagram
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Data transfer Serial vs Parallel
Serial 8 clock time Parallel 1 clock
time
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Serial vs Parallel
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1.3 Introduction to Logic Operations
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NOT, AND, OR
The NOT operation changes one logic level to
the opposite logic level (inverter).
The AND operation produces a HIGH output only
if all the inputs are HIGH.
The OR operation produces a HIGH output when
any of the inputs is HIGH.