1 files changed, 31 insertions, 0 deletions
diff --git a/src/timer.zig b/src/timer.zig
new file mode 100644
index 0000000..21151c7
--- /dev/null
+++ b/src/timer.zig
@@ -0,0 +1,31 @@
+const interrupt = @import("interrupt.zig");
+
+const sys_tick_type = packed struct {
+    enable: u1,
+    tickint: u1,
+    unused: u30,
+
+    rvr: u32,
+    cvr: u32,
+    calib: u32,
+};
+
+var sys_tick: *volatile sys_tick_type = @ptrFromInt(0xE000E010);
+
+pub var ticks_raw: u32 = 0;
+
+pub fn initialize(freq: u32) void {
+    interrupt.register(.SysTick, tick);
+    sys_tick.rvr = 4000000 / 8 / freq;
+    sys_tick.tickint = 1;
+    sys_tick.enable = 1;
+}
+
+fn tick() void {
+    ticks_raw += 1;
+}
+
+pub fn ticks() u32 {
+    return @atomicLoad(u32, &ticks_raw, .acquire);
+}
+