// test4.c
// 利用定时器T0定时10秒，并通过数码管显示秒表，到10秒后让led流水灯从左往右移动
// use timer T0 to count 10 seconds and display the stopwatch on the 7-segment display, and let the led light move from left to right after 10 seconds.
#include "homework6.h"

unsigned char digits[2]  = {0, 0};
unsigned char displayPos = 0;

void test4()
{
    digits[0] = 1;    // set the first digit to 0.
    digits[1] = 0;    // set the second digit to 1.
    TMOD      = 0x01; // set the timer 0 to mode 1.
    TH0       = 0xFC; // set the timer 0 to 1s.
    TL0       = 0x18; // set the timer 0 to 1s.
    TR0       = 1;    // start the timer 0.
    ET0       = 1;    // enable the timer 0 interrupt.
    EA        = 1;    // enable the interrupt.
    while (1) {}
}
void Timer0_ISR() interrupt 1
{
    static unsigned char led    = 0xFE;     // store the led light.
    static unsigned int counter = 0;        // counter to count the number of interrupts.
    TH0                         = 0xFC;     // reset the timer 0.
    TL0                         = 0x18;     // reset the timer 0.
    if (digits[0] == 0 && digits[1] == 0) { // if the stopwatch is 00, let the led light move from left to right.
        set38(TO_LED);                      // set the 38 transistors to the address.

        if (++counter >= 1000) {
            counter = 0;                 // reset the counter.
            led     = (led << 1) | 0x01; // shift the led light to the left.
            if (led == 0xFF) led = 0xFE; // if the led light is 0xFF, reset the led light to 0xFE.
            P2 = led;                    // set the led light.
        }
    } else {
        set38(displayPos);                    // set the 38 transistors to the address.
        P2 = LedChar[digits[1 - displayPos]]; // display the digit.
        displayPos++;                         // switch to the next digit.
        if (displayPos >= 2) displayPos = 0;  // if the display position is 2, reset the display position to 0.
        if (++counter >= 1000) {              // if the counter is 1000, count 1 second.
            counter = 0;                      // reset the counter.
            if (digits[1]-- == 0) {
                digits[1] = 9;
                if (digits[0] > 0) {
                    digits[0]--;
                }
            }
        }
    }
}
void main()
{
    test4();
}