;************************************************************************
; Map the 8259A PIC to use interrupts 32-47 within our interrupt table
;************************************************************************

[bits 32]

global asm_pic_setup
 
%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
 
asm_pic_setup:
 
; 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
	
	;mask
in	al, 0x21		; read in the primary PIC Interrupt Mask Register (IMR)
and	al, 0x00		; 0xEF => 11101111b. This sets the IRQ4 bit (Bit 5) in AL
out	0x21, al		; write the value back into IMR


in	al, 0xA1		; read in the primary PIC Interrupt Mask Register (IMR)
and	al, 0x00		; 0xEF => 11101111b. This sets the IRQ4 bit (Bit 5) in AL
out	0xA1, al		; write the value back into IMR

ret

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