FAT16 ata lba write

ata_lba_write.S

; ata_lba_write - Write a sector to an ATA device using LBA mode
;
; @device: ATA device (0 for primary, 1 for secondary)
; @lba: LBA address of the sector to write
; @buffer: pointer to the buffer containing the data to write
;
; Returns: CF set on error, CF clear on success

global ata_lba_write

section .text

ata_lba_write:
    ; Save registers
    pushad

    ; Backup the LBA
    mov ebx, [lba]

    ; Send the highest 8 bits of the LBA to the hard disk controller
    shr ebx, 24
    or ebx, 0xE0
    mov dx, 0x1F6
    out dx, bl
    ; Finished sending the highest 8 bits of the LBA

    ; Send the total sectors to write
    mov ebx, [buffer]
    mov ecx, dword [ebx]
    mov dx, 0x1F2
    out dx, cl
    ; Finished sending the total sectors to write

    ; Send more bits of the LBA
    mov ebx, [lba]
    mov dx, 0x1F3
    out dx, bl
    ; Finished sending more bits of the LBA

    ; Send more bits of the LBA
    mov ebx, [lba]
    shr ebx, 8
    mov dx, 0x1F4
    out dx, bl
    ; Finished sending more bits of the LBA

    ; Send upper 16 bits of the LBA
    mov ebx, [lba]
    shr ebx, 16
    mov dx, 0x1F5
    out dx, bl
    ; Finished sending upper 16 bits of the LBA

    mov dx, 0x1F7
    mov al, 0x30
    out dx, al

    ; Write all sectors from memory
.next_sector:
    push ecx

; Checking if we need to write
.try_again:
    mov dx, 0x1F7
    in al, dx
    test al, 8
    jz .try_again

; We need to write 256 words at a time
    mov ecx, 256    ; 256 words is 512 bytes (: i.e one sector
    ; ^ Do the outsw instruction 256 times
    mov dx, 0x1F0
    rep outsw   ; Output word from ES:(E)DI to I/O port specified in DX
    ; Writing from "0x0100000" to port 0x1F0
    pop ecx
    loop .next_sector
    ; End of writing sectors from memory
    ret

returns 0 on success and 1 on error. The error code is stored in the CF register.