sbit K1 = P3^7;uchar i,Second_Counts,Key_Flag_Idx;bit Key_State;uchar DSY_CODE[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};void DelayMS(uint ms){ uchar t; while(ms--) { for(t=0;t<120;t++); }}void Key_Event_Handle(){ if(Key_State == 0) { Key_Flag_Idx=(Key_Flag_Idx+1)%3; switch(Key_Flag_Idx) { case 1:EA=1;ET0=1;TR0=1;break; case 2:EA=0;ET0=0;TR0=0;break; case 0:P0=0x3f;P2=0x3f;i=0;Second_Counts=0; } }}void main(){ P0 = 0x3f; P2 = 0x3f; i = 0; Second_Counts = 0; Key_State = 1; TMOD = 0x01; TH0 = (65535-50000)/256; TL0 = (65535-50000)%256; while(1) { if(Key_State != K1) { DelayMS(10); Key_State = K1; Key_Event_Handle(); } }}void DSY_Refresh() interrupt 1{ TH0 = (65535-50000)/256; TL0 = (65535-50000)%256; if(++i==2) { i = 0; ++Second_Counts; P0 = DSY_CODE[Second_Counts/10]; P2 = DSY_CODE[Second_Counts%10]; if(Second_Counts == 100) Second_Counts = 0; }}每句代码的解释含义