1.2 What does“ Digital”Mean? Analog signal Digital signal 4 Infinite possible values - Finite possible values Ex: voltage on a wire ·Ex: button pressed created by microphone on a keypad digital signal analog signal Possible Possible > values. values (U 4 1.00,1.01, 20000009, 2 or 4 That's it infinite time possibilities time 37
37 What Does “Digital” Mean? Analog signal Infinite possible values Ex: voltage on a wire created by microphone value time value time analog signal digital signal • Digital signal – Finite possible values • Ex: button pressed on a keypad 0 1 2 3 4 Possible values: 1.00, 1.01, 2.0000009, ... infinite possibilities Possible values: 0, 1, 2, 3, or 4. That’s it. 1.2
oDigital Logic Design and Application(数字逻辑设计及应用) 1.2 Analog versus Digital (模拟与数字) 模拟量: 其变化在时间或数值 上是连续的 数字量: 其变化在时间和数量 上都是离散的 LL数值大小是某一个最 小数量单位的整数倍 38
38 1.2 Analog versus Digital (模拟与数字) 模拟量： 其变化在时间或数值 上是连续的 数字量： 其变化在时间和数量 上都是离散的 数值大小是某一个最 小数量单位的整数倍 Digital Logic Design and Application (数字逻辑设计及应用)
oDigital Logic Design and Application(数字逻辑设计及应用) 1.2 Analog versus Digital (模拟与数字) PReal signal voice, music, moving picture Analog signal: voltage changed with time L Digital signal sampling values from analog 39
39 1.2 Analog versus Digital (模拟与数字) Digital Logic Design and Application (数字逻辑设计及应用) ◆Real signal : voice,music,moving picture… ◆Analog signal: voltage changed with time ◆Digital signal : sampling values from analog
Digital Signals with Only Two Values: Binary Binary digital signal - only two possible values Typically represented as 0 and 1 L「 time One binary digit is a bit We'll only consider binan digital signals 40
40 40 Digital Signals with Only Two Values: Binary Binary digital signal -- only two possible values Typically represented as 0 and 1 One binary digit is a bit We’ll only consider binary digital signals value time 1 0
Digital Signals with Only Two Values: Binary Binary is popular because 命 Transistors the basic digital electric component, operate using two voltages(more in Chpt. 3) Storing/transmitting one of two values is easier than three or more(e.g, loud beep or quiet beep, reflection or no eflection)
41 41 Digital Signals with Only Two Values: Binary Binary is popular because Transistors the basic digital electric component, operate using two voltages (more in Chpt. 3) Storing/transmitting one of two values is easier than three or more (e.g., loud beep or quiet beep, reflection or no reflection)