边沿触发器的构建原理分析

Construction Principles of Edge-Triggered Flip-Flop

边沿触发器由边沿跳变电路和基本RS锁存器组成。边沿跳变电路根据构建原理可分为基于门延迟和基于正反馈两类。基于门延迟的边沿跳变电路利用边沿检测电路产生脉冲,作为电平触发器的使能信号,脉冲宽度是实现触发器边沿跳变的关键。基于正反馈的边沿跳变电路直接利用正反馈锁0和锁1电路实现边沿跳变。边沿跳变电路产生的信号作为基本RS触发器的输入,实现状态保存。脉冲、正反馈、导通、阻塞这些基本概念的组合,是构成复杂的时序电路的基础。

An edge-triggered Flip-Flop consists of edge transition circuit and basic RS latch, where the edge transition cir- cuit can be grouped into two categories, i.e. gate delay or positive feedback, based on their construction principles. The gate delay ones use edge detection circuit to produce a pulse as the enable signal of a level triggered flip-flop, in which the width of the pulse is the key to implement edge transition, while positive feedback of edge transition circuit accomplishes edge transition with positive feedback 0 latch and 1 latch circuits directly. Signals of edge transition circuit are used as an input of basic RS latch to store states. Composition of basic concepts such as pulse, positive feedback, passing and blocking are the base to construct complex sequential circuits.