用74LS148芯片实现32线-5线优先编码器

Prepare priority encoder of circuit 32-5 with 74LS148 chip

74LS148芯片是8线-3线优先编码器。如果要得到32线-5线优先编码器,可以通过列单块74LS148芯片的简化真值表,列32线-5线优先编码器的简化真值表,找出32线-5线优先编码器的每一个输出与每块74LS148的扩展端YEX的关系,与每块74LS148输出的关系。利用74LSL148的选通输入端S、选通输出端YS、扩展端YEX就可用四块74LS148芯片构成32线-5线优先编码器。

Preparing priority encoder of circuit 32-5 with 74LS148 chip, a priority encoder of circuit 8-3 was introduced. Relationships between eath output of circuit 32-5 priority encoder and esch terminal expansion YEX plus each output of 74LS148 were established through comparing the simplified truth table of single 74LS148 chip and that of circuit 32-5 priority enceder.Then,circuit 32-5 priority encoder could be prepared with four 74LS148 chips by using their strobe input S, strobe output YS, and terminal expansion YEX.