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;************************************************************************
; 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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