// test3.c
// 通过定时器T1中断，实现三位数秒表
// make a three-digit stopwatch by timer T1 interrupt.
#include "homework6.h"

unsigned char digits[3]  = {0, 0, 0}; // store the three digits of the stopwatch.
unsigned char displayPos = 0;         // store the position of the display.

void test3()
{
    TMOD = 0x10; // set the timer 1 to mode 1.
    TH1  = 0xFC; // set the timer 1 to 1s.
    TL1  = 0x18; // set the timer 1 to 1s.
    TR1  = 1;    // start the timer 1.
    ET1  = 1;    // enable the timer 1 interrupt.
    EA   = 1;    // enable the interrupt.
    while (1);
}
void Timer1_ISR() interrupt 3
{
    static unsigned int counter = 0;      // counter to count the number of interrupts.
    TH1                         = 0xFC;   // reset the timer 1.
    TL1                         = 0x18;   // reset the timer 1.
    set38(displayPos);                    // set the 38 transistors to the address.
    P2 = LedChar[digits[2 - displayPos]]; // display the digit.
    displayPos++;                         // switch to the next digit.
    if (displayPos >= 3) displayPos = 0;  // if the display position is 3, reset the display position to 0.
    if (++counter >= 1000) {
        counter = 0; // reset the counter.
        if (++digits[2] >= 10) {
            digits[2] = 0; // reset the third digit.
            if (++digits[1] >= 10) {
                digits[1] = 0; // reset the second digit.
                if (++digits[0] >= 10) {
                    digits[0] = 0; // reset the first digit.
                }
            }
        }
    }
    // reset the stopwatch when the stopwatch is 999.
    if (digits[0] == 9 && digits[1] == 9 && digits[2] == 9) {
        digits[0] = 0;
        digits[1] = 0;
        digits[2] = 0;
    }
}
void main()
{
    test3();
}