Added system clock support

1 files changed, 32 insertions, 0 deletions

diff --git a/src/timer/timer.c b/src/timer/timer.c
new file mode 100644
index 0000000..38f5be6
--- /dev/null
+++ b/src/timer/timer.c
@@ -0,0 +1,32 @@
+#include "../interrupts/interrupts.h"
+#include "../io/io.h"
+
+volatile unsigned int timer_ticks = 0;
+
+void timer_phase(int hz) {
+    int divisor = 1193180 / hz;
+    send(0x43, 0x36); // 01 10 11 0b // CTR, RW, MODE, BCD
+    send(0x40, divisor & 0xFF);
+    send(0x40, divisor >> 8);
+}
+
+// Executed 100 times per second
+void timer_handler(struct regs *r) {
+    timer_ticks++;
+}
+
+// "Delay" function with CPU sleep
+void timer_wait(int ticks) {
+    unsigned int eticks;
+
+    eticks = timer_ticks + ticks;
+    while (timer_ticks < eticks) {
+        __asm__ __volatile__ ("sti//hlt//cli");
+    }
+}
+
+// Install timer handler into IRQ0
+void timer_install() {
+    timer_phase(100);
+    irq_install_handler(0, timer_handler);
+}
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