7.1 接口电路概述 7.2 8253定时计数控制器 7.3 并行接口和可编程并行接口芯片8255A

第1.1节光的电磁理论 一、光是某一波段的电磁波 1.在真空中电磁波的传播速度: 1 C Eo从o

第8章并行接口与应用 8.1并行接口的基本概念 8.2可编程并行接口芯片8255A 8.3可编程并行接口芯片8155 8.4单片机与键盘和数码管显示器的接口电路

Synchronous sequential circuit memory, usually consisting of flip-flops, update circuit states information All flip-flops share a common clock pulse input The clock input is not a binary value representing the time of day but rather a\synchronous\train of pulses. Synchronous memory changes its data only at certain time intervals The flip-flops can change state only on a clock pulse edge

信噪比：衡量一个信号质量优劣的指标。它是在指定频带内，同一端口信号功率

Analysis Analyze existing circuits to determine their function Synchronous sequential circuit The basic modeling structure Two circuit models: Mealy model& Moore model Three approach used to describe the circuit: Logic function equation

Sequential Circuit Models Yo Combinational logic Universal combinational circuit model No memory units No feedback from logic outputs back to the inputs

Registers, formed from collection of flip -flops, are used to store or manipulate data or both. Input and output function associated with registers include Parallel input/ Parallel output Serial input/ Serial output Parallel input/ Serial output OSerial input parallel output

前面的讨论中,假设了yr=0,实际上y≠0,因而将引起内部反馈,使放大器不稳定甚至自激

simple counters Counting is a fundamental function of digital circuits. A digital counter consists of a collection of flip-flops that change states (set or reset) in a prescribed sequence