1 files changed, 67 insertions, 0 deletions
diff --git a/kernel/pic.asm b/kernel/pic.asm
new file mode 100644
index 0000000..ecbab64
--- /dev/null
+++ b/kernel/pic.asm
@@ -0,0 +1,67 @@
+;************************************************************************
+; Map the 8259A PIC to use interrupts 32-47 within our interrupt table
+;************************************************************************
+ 
+%define ICW_1 0x11				; 00010001 binary. Enables initialization mode and we are sending ICW 4
+ 
+%define PIC_1_CTRL 0x20				; Primary PIC control register
+%define PIC_2_CTRL 0xA0				; Secondary PIC control register
+ 
+%define PIC_1_DATA 0x21				; Primary PIC data register
+%define PIC_2_DATA 0xA1				; Secondary PIC data register
+ 
+%define IRQ_0	0x20				; IRQs 0-7 mapped to use interrupts 0x20-0x27
+%define IRQ_8	0x28				; IRQs 8-15 mapped to use interrupts 0x28-0x36
+ 
+MapPIC:
+ 
+; Send ICW 1 - Begin initialization -------------------------
+ 
+	; Setup to initialize the primary PIC. Send ICW 1
+ 
+	mov	al, ICW_1
+	out	PIC_1_CTRL, al
+ 
+; Send ICW 2 - Map IRQ base interrupt numbers ---------------
+ 
+	; Remember that we have 2 PICs. Because we are cascading with this second PIC, send ICW 1 to second PIC command register
+ 
+	out	PIC_2_CTRL, al
+ 
+	; send ICW 2 to primary PIC
+ 
+	mov	al, IRQ_0
+	out	PIC_1_DATA, al
+ 
+	; send ICW 2 to secondary controller
+ 
+	mov	al, IRQ_8
+	out	PIC_2_DATA, al
+ 
+; Send ICW 3 - Set the IR line to connect both PICs ---------
+ 
+	; Send ICW 3 to primary PIC
+ 
+	mov	al, 0x4			; 0x04 => 0100, second bit (IR line 2)
+	out	PIC_1_DATA, al		; write to data register of primary PIC
+ 
+	; Send ICW 3 to secondary PIC
+ 
+	mov	al, 0x2			; 010=> IR line 2
+	out	PIC_2_DATA, al		; write to data register of secondary PIC
+ 
+; Send ICW 4 - Set x86 mode --------------------------------
+ 
+	mov	al, 1			; bit 0 enables 80x86 mode
+ 
+	; send ICW 4 to both primary and secondary PICs
+ 
+	out	PIC_1_DATA, al
+	out	PIC_2_DATA, al
+ 
+; All done. Null out the data registers
+ 
+	mov	al, 0
+	out	PIC_1_DATA, al
+	out	PIC_2_DATA, al
+