最新八路抢答器实训报告.docx

County continuation records has examined and approved the draft, spirit, believe, comprehensive Yearbook of zhuanglang a
根本原理
S1-8为八位选手的抢答开关，SW1单刀双掷开关设为主持人控制开关。当主持人控制开关置于清零状态时，RS触发器的R端为低电平，输出端全部为低电平。于是4511的BI为高，显示器灭灯；74LS148处于工作状态。当SW1置于开始状态，优先编码电路和锁存电路同时处于工作状态。74LS279的1R、1S均为高电平，由真值表可知，输出1Q为低电平，从而使74LS148输入使能端为低电平有效，即抢答器处于等待工作状态。假设有选手〔假设为3号选手〕按动抢答开关〔即闭合S4〕，此时优先编码器74LS148输入端I3接低电平有效，那么输出A2A1A0为100，A2A1A0分别接至3S、2S、1S，根据RS锁存器真值表，1Q2Q3Q输出分别为110，从而4511的输入端DCBA为0011，经4511译码，显示器上显示“3
County continuation records has examined and approved the draft, spirit, believe, comprehensive Yearbook of zhuanglang already prepared draft, entered the phase of evaluation. Civil air defense work2
County continuation records has examined and approved the draft, spirit, believe, comprehensive Yearbook of zhuanglang already prepared draft, entered the phase of evaluation. Civil air defense work3
County continuation records has examined and approved the draft, spirit, believe, comprehensive Yearbook of zhuanglang already prepared draft, entered the phase of evaluation. Civil air defense work
〞。与此同时，当74LS148输入端有一个为低电平时，GS为低电平有效，即标志译码器处于工作状态，从而使4S为0，此时4Q输出为高电平，致使EI为高电平，74LS148处于禁止工作状态，即输入不受允许。实现了优先抢答有效的功能。抢答结束后，主持人拨动开关清零，数码管不亮，即恢复初始状态，进入下一轮抢答环节。
抢答器电路图
总体框图
抢答器原理图
2 各功能电路实现原理及电路设计
抢答电路的功能有：分辨出选手按按钮的先后，并锁存优先抢答者的编号，供译码显示电路用；要使其他选手的按钮操作无效。因此，选用优先编码器74LS148、 RS锁存器74LS279、译码显示电路4511、报警电路74LS86以及74LS27完成上述功能。下面简述一下重要芯片的作用以及芯片管脚。
74LS148
74LS148 为 8 线－3 线优先编码器，共有 54/74148 和 54/74LS148 两种线路结构型式， 将 8
County continuation records has examined and approved the draft, spirit, believe, comprehensive Yearbook of zhuanglang already prepared draft, entered the phase of evaluation. Civil air defense work6
County continuation records has examined and approved the draft, spirit, believe, comprehensive Yearbook of zhuanglang already prepared draft, entered the phase of evaluation. Civil air defense work3
County continuation records has examined and a