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Code: Select all

; input: 
;   dl -> device
;   es:bx -> Buffer to read to
;   ax -> Start sector
;   cx -> Number of sectors
;
; output:
;   carry -> On error

fat_read_device:
    mov di, FAT_READ_RETRIES ; retries for error -> 5

    .try_load:
        push ax
        push bx
        push cx

        push bx
        mov bl, dl ; remember device
        mov dx, ax

        int 0xe2 ; Convert lba to chs -> Writing to cl, ch and dh

        mov dl, bl
        pop bx

        mov ah, 0x02 ; Read device es:bx
        mov al, 0x01 ; Number of sectors to read
        ;xchg bx, bx
        int 0x13
        jnc .done ; test if succeeded

        xor ax, ax ; Reset disk
        int 0x13
        dec di ; decrement error counter
        pop cx
        pop bx
        pop ax
        jnz .try_load ; attempt to read again

        stc
        ret

    .done:
        int 0xcf ; Feedback disk operation -> Print a '.'

        pop cx
        pop bx
        pop ax
        add bx, word [bpbBytesPerSector] ; next sector
        inc ax ; read next sector
        loop fat_read_device ; repeat until cx sectors are read
        ret

Code: Select all

timer_init:
    cli 

    mov al, 36h ; PIT channel 0
    out 43h, al ; select channel

    mov ax, TIMER_DIVISOR
    out 40h, al ;send low byte
    mov al, ah
    out 40h, al ;send high byte

    sti

    mov word [cs:timer_tick_count], 0

    ret

Code: Select all

    ; Set low byte
    mov al, 0x0f
    mov dx, 0x03d4
    out dx, al

    mov al, bl 
    mov dx, 0x03d5
    out dx, al

    ; Set high byte
    mov al, 0x0e
    mov dx, 0x03d4
    out dx, al

    mov al, bh
    mov dx, 0x03d5
    out dx, al