程序补充说明：时钟输入：在每个时钟的正沿或负沿对数据进行处理。时钟的正沿有效还是负沿有效，是由always敏感表中的posedge或negedge决定的 -Procedures for additional information: Clock Input: in each clock is along or negative along the data treatment. Clock is along the effective or negative along the effectiv