Ch 1. Introduction

Ch 1. Introduction

• 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

• Analog Signal

– Continuous voltage– Unwanted noise– Can’t transmit data at long distance

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 OUTPUTA B Y

0 0 0

0 1 0

1 0 0

1 1 1

INPUT OUTPUTA B Y

0 0 0

0 1 1

1 0 1

1 1 1

2 input AND gate

2 input OR gate

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

1.4 Electronic Aspects of Digital Design

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 이전- Layout editor 나 Schematic editor 를 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

• HDL - Hardware Description Language- 1980 년대 초부터 미 국방성에서 사용시작- 1981 년 VHDL (VHSIC Hardware Description Language) 제안 , 이후 IEEE 표준으로 채택

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

𝐖𝐡𝐞𝐧𝑺=𝟎 ,𝒁=𝑨𝐖𝐡𝐞𝐧𝑺=𝟏 ,𝒁=𝑩

input output

𝐖𝐡𝐞𝐧𝑺=𝟎 ,𝒁=𝑨𝐖𝐡𝐞𝐧𝑺=𝟏 ,𝒁=𝑩

𝒔

Turn on when ‘0’

Turn on when ‘1’

output

input

2-input 4-bit MUXInput : A and B (0~4bits) Output : Z (0~4bits)

𝐖𝐡𝐞𝐧𝑺=𝟎 ,𝒁=𝑨𝐖𝐡𝐞𝐧𝑺=𝟏 ,𝒁=𝑩

𝐖𝐡𝐞𝐧𝑺=𝟎 ,𝒁=𝑨𝐖𝐡𝐞𝐧𝑺=𝟏 ,𝒁=𝑩

Conditional operator