本文件是周立功试验开发板的配套资料，容易学会-This document is ZLG test development board supporting information, easy to learn

利用quatars,vhdl实现有倒计时功能计时器，设计定时器功能有正向计时和倒向计时，可暂停计数，继续计数。当倒向计时计数为0时会报警（时间为1分钟）在报警期间可以认为关闭-Using quataus, VHDL realization which has the function of the countdown counter, timer design features are timing and backward timin