Adding code

1 files changed, 20 insertions, 0 deletions

diff --git a/include/07.pit/pit03.c b/include/07.pit/pit03.c
new file mode 100644
index 0000000..287adba
--- /dev/null
+++ b/include/07.pit/pit03.c
@@ -0,0 +1,20 @@
+void init_timer(uint32_t frequency)
+{
+    // Firstly, register our timer callback.
+
+    // The value we send to the PIT is the value to divide it's input clock
+    // (1193180 Hz) by, to get our required frequency. Important to note is
+    // that the divisor must be small enough to fit into 16-bits.
+    uint32_t divisor = 1193180 / frequency;
+
+    // Send the command byte.
+    ioport_out(0x43, 0x36);
+
+    // Divisor has to be sent byte-wise, so split here into upper/lower bytes.
+    uint8_t l = (uint8_t)(divisor & 0xFF);
+    uint8_t h = (uint8_t)( (divisor>>8) & 0xFF );
+
+    // Send the frequency divisor.
+    ioport_out(0x40, l);
+    ioport_out(0x40, h);
+}