定时计数器实验和中断练习

#include
void init(void); //initiation
unsigned char counter_2000ms;
unsigned char th;
unsigned char tl;
bit ff; //flag
main()
{
init(); //initiation of the MCU
while(1) //查询、等待
{
if (ff==0) //ff=0 no thing
{
}
else // ff=1
{
counter_2000ms = 0;
P0=~P0;
ff = 0;
}
}
}
void T0_50ms() interrupt 1
{
EA = 0; //interrupt masked
TH0 = th; //reload
TL0 = tl;
counter_2000ms++;
if (counter_2000ms==40) ff=1; //2.0sec. is on
EA = 1; //interrupt enabled
}
//
void init(void)
{
IE |= 0x82; //T0 enabled
// EA = 1; //enabled all interrupts
// ET0 = 1; //external interrupt ebnabled
TMOD = 0x01; // 16-bit timer
th = 0x3c;
tl = 0xb0;
TH0 = th;
TL0 = tl;
P0 = 0x55;
/**********************************************
;12MHz/12=100 0000Hz, t=1 us
;50ms=50 000 us, 50 000/1=50 000
;65536-50 000=15536=3cb0h, TH0=3ch, TL0=b0h,
;interupt gets 50ms
; 2.0sec=2000ms, 2000/50=40
;**********************************************/
counter_2000ms=0x00;
ff = 0;
TR0 = 1; //start t0
}

练习：
P1口上接有8只LED。在外部输入引脚P3.2和P3.3上各接有一只
按钮开关K1和K2。程序要求K1和K2都未按下时，P1口的8只LED呈
流水灯显示，仅K1（P3.2）按下时，左右4只LED交替闪烁一次。仅按
下K2（P3.3）时，P1口的8只LED全闪亮。两个外中断的优先级相同。