用51汇编语言设计的DTMF发生器程序 输出到PI的每次间隔是52个指令周期 主频：6M，6M/12=0.5M,每个指令周期：2uS 即每次输出到P1的时间间隔是122uS 指令周期数：52 + 9 = 61-51 assembly language using the design process DTMF generator output to the PI for each interval is 52 instruction cycle speeds : 6M, 6M/12 = for 0.5 per instruction cycle : 2uS that each output to the P1 time interval is 122uS instruction cycle : 52 9 = 61