diff options
Diffstat (limited to 'mubios/arch/irq.S')
| -rw-r--r-- | mubios/arch/irq.S | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/mubios/arch/irq.S b/mubios/arch/irq.S index 6eea350..dbde8ad 100644 --- a/mubios/arch/irq.S +++ b/mubios/arch/irq.S @@ -20,6 +20,12 @@ .intel_syntax noprefix .code16 + .equ BDA_TIMER_COUNTER, 0x046C + .equ BDA_TIMER_ROLLOVER, 0x0470 + + .equ TIMER_TICKS_PER_DAY_LOW, 0x00B0 + .equ TIMER_TICKS_PER_DAY_HIGH, 0x0018 + .section .text16.irq, "ax" .global irq0_entry @@ -27,11 +33,34 @@ irq0_entry: push ax + push bx + + xor bx, bx + mov ds, bx + + mov bx, BDA_TIMER_COUNTER + inc word ptr [bx] + + jnz irq0_send_eoi + + inc word ptr [bx + 2] + + cmp word ptr [bx + 2], TIMER_TICKS_PER_DAY_HIGH + jne irq0_send_eoi + + cmp word ptr [bx], TIMER_TICKS_PER_DAY_LOW + jne irq0_send_eoi + + mov word ptr [bx], 0 + mov word ptr [bx + 2], 0 + mov byte ptr [BDA_TIMER_ROLLOVER], 1 +irq0_send_eoi: # Acknowledge IRQ0 on the master PIC. mov al, 0x20 out 0x20, al + pop bx pop ax iret |