archieve: homework6 test3

homework6/src/homework6.h

@@ -69,4 +69,5 @@ void set38(unsigned char addr)
     ADDR0 = addr & 0x01;
     ADDR1 = (addr & 0x02) >> 1;
     ADDR2 = (addr & 0x04) >> 2;
-}
+}
+// low seg is the right side.

homework6/src/test3.c

@@ -0,0 +1,50 @@
+// 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();
+}