1、L7~L11实现12分钟倒计时，初始显示12-00，L13和L14实现24秒倒计时初始显示24，两种倒计时同时进行；

2、按键K1控制分钟倒计时暂停、开始，按键K2控制分钟倒计时复位，复位值为12-00；

3、按键K3控制24秒倒计时暂停、开始，K4键控制24秒倒计时复位，复位值为24，24秒倒计时终了蜂鸣器长鸣1s；

4、当分钟位剩余时间不足24秒时，停止24秒倒计时；

5、当24秒倒计时剩3秒时，每减1秒，蜂鸣器响一次；12分钟计时结束，蜂鸣器长鸣1s。-1, L7~L11 a 12-minute countdown, the initial display 12-00,L13 and L14 24 and counting the initial display 24, two countdown at once

2, press the key K1 minute pause, start the countdown, press K2 control minutes countdown reset, reset values of 12-00

3, press the K3 control 24-second countdown pause, start, K4 control 24-second countdown reset, reset values of 24, ending 24-second countdown beeper ringing 1s

4, when the remaining time is less than 24 minutes seconds, stopping 24-second countdown

5, when the 24-second countdown with 3 seconds left, every 1 second reduction, the buzzer sounded　a 12-minute timers, buzzer Bell 1s.