[bits 16]
org 100h
dma_status      equ     0d0h
dma_command     equ     0d0h    
dma_mask        equ     0d4h  ;was 0ah
dma_mode        equ     0d6h
dma_clear       equ     0d8h  ;was 0ch
dma_offset      equ     0c8h    ;was 04
dma_page        equ     089h    ;was 081h
dma_length      equ     0cah    ;was 05h
        mov dx, dma_status;08h
        in al, dx       ;dma status register: bits 7-4 tell if a dma channel
        mov cx, 0
waiting4dma:
        test al, 0f0h   ;is in use
        jz dma_notbusy
        loop waiting4dma

dma_notbusy:
        ;************ mask ch2 to set it up **************
        mov al, 6       ;6 = 110 or set mask(1) for ch2 (10)
        out dma_mask, al;dma mask register: must mask dma channel before
                        ;setting it up.
        ;************ stop any dma transfers **************
        xor al, al      ;The dma wait waited for any dma transfers, now stop
        out dma_clear, al     ;dma transfers (shouldn't interfere now)
        ;************ setup mode register ***************
        mov al, 086h    ;block mode(10),incmem(0),autoini(0),write(01),ch2(10)
        out dma_mode, al;=10000110xb=86h; 0bh=mode port; write operation b/c
                        ;writing to mem (not writing to device)
        ;************ setup offset **************
        mov bx, ds      ;need to take low 12 bits of ds into account
        and bx, 0fffh
        shl bx, 4
        mov ax, buffer  ;ax = offset w/out low 12 bits segment, (doesn't use
        add ax, bx      ;segments, uses pages (high 4 bits seg))
        out dma_offset, al     ;low byte of offset
        mov al, ah
        out dma_offset, al     ;high byte of offset
        ;************ setup page **************
        mov ax, ds      ;get ready for page
        and ax, 0f000h  ;only need high 4 bits
        shr ax, 12      ;mov to al
        out dma_page, al    ;ch2 page port
        ;************ setup length of transfer **************
        mov al, 1
        out dma_length, al
        xor al, al
        out dma_length, al
        ;************ send dma command ****************
        ;mov al, 
        ;************ unclear ch2 mask bit ***********
        mov al, 2       ;set al for ch2, bit2 = 0 to indicate to clear mask
        out dma_mask, al     ;unmask ch2 on mask register

        ;mov al, 6       ;bit2=1=request, bits1,0=10=ch2
        ;out 09h, al     ;write request port: set to request a write transfer
        ;********* DMA COMPLETE ************
        ;********* SETUP HD **********
	call wait4ready
        jnc setCHS_drv_head
        jmp error
setCHS_drv_head:
	mov dx, 01f6h
	mov al, 0a0h   ;10100000xb = CHS, Drive 0, Head 0
	out dx, al
	
	call wait4ready
        jnc maskirq
        jmp error

maskirq:
	mov dx, 0a1h	;irq masking register
	in al, dx
	or al, 040h	;01000000xb = mask irq14
	out dx, al

	mov ah, 8
	mov dl, 80h
	int 13h		;Get drive parameters, return: dh=physical # heads
	cmp dh, 8	;For some reason, if < 8 heads, say 0, if >= say 8
	jae changeto8heads
	xor al, al
	jmp outputphysicalheads
changeto8heads:	mov al, 8
outputphysicalheads:	mov dx, 0376h
	out dx, al
	
	;If there was a precompensation cylinder, it would go to port 01f1h
	;but for now keep it simple. (precomp cylinder would be divided by 4)

	mov dx, 01f2h		;Set #sectors = 1
	mov al, 1
	out dx, al
	
	inc dl
	out dx, al		;sector # = 1

	inc dl
	dec al
	out dx, al		;cylinder low = 0

	inc dl
	out dx, al		;cylinder high = 0

	inc dl
	mov al, 0a0h		;=10100000xb=1,CHS,1,drive 0, head 0000
	out dx, al

        ;******** issue the command ************
        inc dl
        mov al, 0c8h    ;read dma w/ retry
        out dx, al
        ;******** wait until transfer done ********
        mov cx, 10
outside_waiting4read:
        push cx
        mov cx, 0
waiting4read:   loop waiting4read
        pop cx
        loop outside_waiting4read
;still_reading:
;        in al, dx
;        test al, 128    ;see if bit7 set = busy
;        jnz still_reading
        ;********* check for error ***************
        mov dx, 01f7h
        in al, dx
        test al, 1
        jnz error

        mov dx, buffer
        mov ah, 9
        int 21h

        jmp done
;*********************** Called procedures ************************
error:
        mov dx, 01f1h
        in al, dx
        inc al
        inc al
        mov dl, al
        mov ah, 2
        int 21h

        mov dx, err_message
	mov ah, 9
	int 21h
	
done:
	mov dx, 0a1h	;irq masking register
	in al, dx
        and al, 0bfh     ;10111111xb = unmask irq14
	out dx, al

        mov ax, 4c00h
        int 21h
err_message	db	"Error in waiting...$"
	;******************
wait4ready:
	pusha
	mov dx, 01f7h
        mov cx, 0
waitloop:
	in al, dx
        and al, 040h    ;01000000xb = drive ready
        cmp al, 040h
        jz ready
	push cx
	xor cx, cx
pause:	loop pause
	pop cx
	loop waitloop
	stc		;store carry flag as a return error
ready:
	popa
	ret
        
;********************* DATA **********************
buffer  TIMES 80h       dd      0       ;reserve 512 bytes for sector
endbuffer       db      "$"