From f6858b7333139441215e83e070e098bf09056762 Mon Sep 17 00:00:00 2001
From: Jake Mannens <jake72360@gmail.com>
Date: Tue, 19 Jun 2018 05:22:54 +1000
Subject: Added foundation code to initialize the PIT and create a 10ms jiffies
 counter.

---
 kernel/timer.s | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 kernel/timer.s

(limited to 'kernel/timer.s')

diff --git a/kernel/timer.s b/kernel/timer.s
new file mode 100644
index 0000000..de01ea6
--- /dev/null
+++ b/kernel/timer.s
@@ -0,0 +1,34 @@
+global timer_init
+extern register_isr
+
+; TODO: move this someplace safe (not kmain.c)
+extern ticks
+
+tick_handler:
+  push ax
+  inc dword [ticks]
+  mov al, 0x20
+  out 0x20, al
+  pop ax
+  iret
+
+timer_init:
+  push ebp
+  mov ebp, esp
+  ; register the tick_handler
+  push tick_handler
+  push dword 0x20
+  call register_isr
+  add esp, 8
+  ; initialize the pit
+  mov ax, 0x36
+  out 0x43, al
+  mov ax, 0x2E9C ; 10ms tick interval
+  out 0x40, al
+  mov al, ah
+  out 0x40, al
+  in al, 0x21
+  and al, 0xFE
+  out 0x21, al
+  pop ebp
+  ret
-- 
cgit v1.3