// test4.c
// 写一个从999999开始倒计时的秒表。并且改用定时器T1的中断来完成
// make a stopwatch that counts down from 999999. and use interrupt to finish it.

#include "homework5.h"
unsigned char LedBuff[6]            = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}; // buffer to store the seg chars.
volatile unsigned char i            = 0;                                    // to current digit.
volatile unsigned long display_time = 999999;                               // to store the time to display.
unsigned int cnt                    = 0;                                    // to count interrupt.

// init timer
void initTimer(void)
{
    TMOD &= 0x0F; // clear TMOD.
    TMOD |= 0x10; // set TMOD to mode 1.
    TH1 = 0xFC;   // 1ms timer.
    TL1 = 0x18;
    ET1 = 1; // enable timer 1 interrupt.
    EA  = 1; // enable global interrupt.
    TR1 = 1; // start timer 1.
}

// timer1 interrupt service routine.
void timer1ISR(void) interrupt 3
{
    TH1 = 0xFC; // reset timer.
    TL1 = 0x18;

    // display the number.
    set38Transistors(i);
    P2 = LedBuff[i];
    i  = (i + 1) % 6; // to switch to the next digit.

    // 1s timer.
    if (++cnt >= 1000) { // if reached 1s.
        cnt = 0;
        if (display_time > 0) {
            display_time--; // decrease the time.
        }
    }
}

void test4()
{
    initTimer();
    while (1) {
        // split the time into 6 digits.
        unsigned char first_digit  = display_time / 100000;           // to get the first digit.
        unsigned char second_digit = (display_time % 100000) / 10000; // to get the second digit.
        unsigned char third_digit  = (display_time % 10000) / 1000;   // to get the third digit.
        unsigned char fourth_digit = (display_time % 1000) / 100;     // to get the fourth digit.
        unsigned char fifth_digit  = (display_time % 100) / 10;       // to get the fifth digit.
        unsigned char sixth_digit  = display_time % 10;               // to get the sixth digit.

        // load the number in the buffer.
        // 5 is high digit.
        // 0 is low digit.
        LedBuff[5] = LedChar[first_digit];  // to display the first digit.
        LedBuff[4] = LedChar[second_digit]; // to display the second digit.
        LedBuff[3] = LedChar[third_digit];  // to display the third digit.
        LedBuff[2] = LedChar[fourth_digit]; // to display the fourth digit.
        LedBuff[1] = LedChar[fifth_digit];  // to display the fifth digit.
        LedBuff[0] = LedChar[sixth_digit];  // to display the sixth digit.
    }
}

void main()
{
    test4();
}