diff --git a/homework6/.eide/eide.json b/homework6/.eide/eide.json
index 1a60965..819918d 100644
--- a/homework6/.eide/eide.json
+++ b/homework6/.eide/eide.json
@@ -20,7 +20,8 @@
     "Debug": {
       "excludeList": [
         "src/test1.c",
-        "src/test2.c"
+        "src/test2.c",
+        "src/test3.c"
       ],
       "toolchain": "Keil_C51",
       "compileConfig": {
diff --git a/homework6/src/test4.c b/homework6/src/test4.c
index 5358bf3..a46bb86 100644
--- a/homework6/src/test4.c
+++ b/homework6/src/test4.c
@@ -3,10 +3,52 @@
 // 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();