--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/timer.c	Thu Mar 31 23:25:52 2016 -0700
@@ -0,0 +1,43 @@
+#include <stdint.h>
+#include <string.h>
+#include <limits.h>
+#include "timer.h"
+
+void timer_init(timer *context, uint32_t clock_div)
+{
+	memset(context, 0, sizeof(timer));
+	context->clock_inc = clock_div;
+}
+
+void timer_run(timer *context, uint32_t target)
+{
+	while (context->cycles < target)
+	{
+		if (context->current) {
+			context->current--;
+			if (!context->current) {
+				context->pending = 1;
+			}
+		} else {
+			context->current = context->load;
+		}
+		context->cycles += context->clock_inc;
+	}
+}
+
+uint32_t timer_next_interrupt(timer *context)
+{
+	if (context->pending) {
+		return 0;
+	}
+	if (context->current) {
+		return context->cycles + context->current * context->clock_inc;
+	}
+	return UINT_MAX;
+}
+
+void timer_write(timer *context, uint16_t value)
+{
+	context->load = context->current = value;
+	context->pending = 0;
+}