;;;;;;;;;;;;;
; Constants ;
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;;;;;;;;;;;;;
; Functions ;
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setupDMAChannel:
; Set up DMA Channel
; In:
;	channel (byte, 0..3)
;	mode (byte)
;	start offset (word)
;	page (word)
;	count (word)
; Out: none
push bp
mov bp, sp
; Disable channel 2
mov al, [bp + 4]
or al, 100b
out 0ah, al
; Set mode
mov al, [bp + 5]
or al, [bp + 4]
out 0bh, al
; Select address register
xor dh, dh
mov dl, [bp + 4]
shl dl, 1
out 0ch, al
; Set offset
mov ax, [bp + 6]
out dx, al
mov al, ah
out dx, al
; Set count
inc dl
mov ax, [bp + 10]
dec ax
out dx, al
mov al, ah
out dx, al
; Set page
xor bh, bh
mov bl, [bp + 4]
mov dl, [cs:_dma_page_registers + bx]
mov al, [bp + 8]
out dx, al
; Enable channel 2
mov al, [bp + 4]
out 0ah, al
pop bp
ret

;;;;;;;;
; Data ;
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section .data

_dma_page_registers db 87h, 83h, 81h, 82h