DX200中波发射机控制板卡时钟电路解析

摘要

DX200 medium wave transmitter's control board has a stepping sequence control function when the transmitter starts. Also it monitors the power amplifier unit and gives protective response to the faults of internal and external parts, etc. In order to make every control circuit coordinately work on time, we have adopted a 555 in-tegrated timer which constitutes an astable free-running multivibrator with peripheral resistance and capacitance. The multivibrator generates an 8 KHZ clock signal. Frequency divider made with 74 hc161 synchronous counting units produces 4 KHZ, 128 HZ, 64 HZ, 16 HZ and 1/64 HZ, sends them to each PAL and programmable logic de-vices, and then provides corresponding control. Based on 555 integrated timer and 74 hc161 synchronous counter, the paper introduces in detail the structure and internal principle and their functions, and elaborates the generating principle of the transmitter control board's clock circuit.%DX200中波发射机控制板为发射机提供开机时步进起动的顺序控制，还对功放单元进行监视，对内部外部的故障情况进行保护性响应等，为了使各个部分控制电路在时间上能够协调的工作，我们采用一只555集成定时器与外围电阻、电容构成一个无稳态自激多谐振荡器，使其产生8KHZ的时钟信号。利用74HC161同步计数机组成分频器产生的4kHz，128Hz，64Hz，16Hz，1/64Hz发送到每个PAL和可编程逻辑器件，提供相应的控制。本文详细介绍了555集成定时器和74HC161同步计数器的结构组成、内部原理及其功能，阐述了发射机控制板卡时钟电路产生的原理。