Ch 1. Introduction
• Analog Signal
– Continuous voltage
– Unwanted noise
– Can’t transmit data at long distance
• Digital Signal
–
–
–
–
–
‘0’ &’1’, ‘False’ & ‘True’, ‘High’ & ‘Low’
Enables transmission of signals over a long distance
More secure
Lower electromagnetic interference
Enables Multi-directional transmission simultaneously
1.3 Digital Devices
• Gate
– The most basic digital devices
– Got there name from their function (AND, OR…)
– Gate has one or more inputs and produces output
that is function of current input values
INPUT
2 input AND gate
OUTPUT
A
B
Y
0
0
0
0
1
0
1
0
0
1
1
1
INPUT
2 input OR gate
OUTPUT
A
B
Y
0
0
0
0
1
1
1
0
1
1
1
1
1.4 Electronic Aspects of Digital Design
Logic Function
Electronic Function
• Noise Margin
– The voltage difference between the guaranteed output level
and the required input voltage of a logic gate
– In a real circuit, a gate’s output can be corrupted by this
much noise
1.5 Software Aspects of Digital Design
Software Tools
 CAD
 Schematic Diagram
 HDLs
 Text editors
 Compilers
 Synthesizers
 Simulators
 Test Benches
 Timing Analyzers
Ex) Modelsim, Xilinx, Synplify, XST
• HDL
- Hardware Description Language
- 1980년대 초부터 미 국방성에서 사용시작
- 1981년 VHDL (VHSIC Hardware Description Language) 제안,
이후 IEEE 표준으로 채택
• HDL 이전
- Layout editor나 Schematic editor를 사용
- 작은 블록을 설계하고 큰 블록을 설계하는 Bottom-up 방식
- 회로의 규모가 커지고 복잡도가 증가함에 따라 한계 발생
• HDL 이후
- 알고리즘이나 기능 레벨에서 설계가 가능
- Top-down 방식
- 복잡한 회로의 설계 가능
1.6 Integrated Circuits
• IC (Integrated Circuit)
– Collection of one or more gates fabricated on a single silicon chip
– SSI (Small Scale IC) →MSI (Medium Scale IC) →LSI (Large Scale IC)
→ VLSI (Very Large Scale IC)→SoC (System on Chip)
→ NoC (Network on Chip)
– pad, die
Pin diagrams are used only for mechanical reference
1.7 Programmable Logic Devices
PLA (Programmable logic array) : Only two level structure (AND, OR)
PAL (Programmable array logic), PLD(Programmable logic device)
→CPLD(Complex PLD)→FPGA(Field-programmable gate array)
1.10 Digital-Design Levels
input
𝐖𝐡𝐞𝐧 𝑺 = 𝟎, 𝒁 = 𝑨
𝐖𝐡𝐞𝐧 𝑺 = 𝟏, 𝒁 = 𝑩
output
Turn on when ‘0’
output
input
𝒔
Turn on when ‘1’
𝐖𝐡𝐞𝐧 𝑺 = 𝟎, 𝒁 = 𝑨
𝐖𝐡𝐞𝐧 𝑺 = 𝟏, 𝒁 = 𝑩
2-input 4-bit MUX
Input : A and B (0~4bits)
Output : Z (0~4bits)
𝐖𝐡𝐞𝐧 𝑺 = 𝟎, 𝒁 = 𝑨
𝐖𝐡𝐞𝐧 𝑺 = 𝟏, 𝒁 = 𝑩
𝐖𝐡𝐞𝐧 𝑺 = 𝟎, 𝒁 = 𝑨
𝐖𝐡𝐞𝐧 𝑺 = 𝟏, 𝒁 = 𝑩
Conditional operator
𝒁 = 𝐂𝐨𝐧𝐝𝐢𝐭𝐢𝐨𝐧 ? 𝐓𝐫𝐮𝐞: 𝐅𝐚𝐥𝐬𝐞