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HELLO,

I AM DEVELOPING A IDE DEVICE DRIVER, AND MY HARD DISK IS ATTACH AT SECONDARY MASTER OF IDE.
THE BELOW CODE IS A PORTION OF BOOT SECTOR CODE OF MY DRIVER THAT READS A SINGLE SECTOR. MY PROBLEM WITH THIS CODE IS THAT IT IS EXECUTING IN ENDLESS LOOP, IN SHORT IT DOES NOT WORK. MY GUESS IS THAT THE VARIABLE "drive" is having wrong value.

In the upper part of my code I have this code
%define drive bp+40

and in the start of the code I have this
mov bp, 7C00H
mov [bp+40], dl ;THEY SAY BIOS PUT THE VALUE IN DL WHERE IT BOOTS.

I HAVE TRIED THIS VALUES TO PUT IN drive, 80H, 81H, 82H, 83H, 8EH, 8FH BUT TO NO AVAIL.

; Read one sector from disk, using LBA
; input:   EAX - 32-bit DOS sector number
;      ES:BX - destination buffer
;      (will be filled with 1 sector of data)
; output:   ES:BX points one byte after the last byte read.
;      EAX - next sector
mov cx, 1 ;one sector to read
readDisk:   push   dx
      push   si
      push   di

read_next:   push   eax   ; would ax be enough?
      mov   di, sp   ; remember parameter block end

;---      db   0x66   ; operand size override (push dword)
      push   byte 0   ;XXX   ; other half of the 32 bits at [C]
            ; (did not trust "o32 push byte 0" opcode)
      push   byte 0   ; [C] sector number high 32bit
      push   eax   ; [8] sector number low 32bit
      push   es   ; [6] buffer segment
      push   bx   ; [4] buffer offset
      push   byte 1   ; [2] 1 sector (word)
      push   byte 16   ; [0] size of parameter block (word)
      mov   si, sp
      mov   dl, [drive]
      mov   ah, 42h   ; disk read
      int   0x13   

      mov   sp, di   ; remove parameter block from stack
            ; (without changing flags!)
      pop   eax   ; would ax be enough?

      jnc   read_ok      ; jump if no error

      push   ax         ; !!
      xor   ah, ah      ; else, reset and retry
      int   0x13
      pop   ax         ; !!
      jmp   read_next

read_ok:   inc    eax         ; next sector
      add   bx, word [bsBytesPerSec]
      jnc   no_incr_es      ; if overflow...

      mov   dx, es
      add   dh, 0x10      ; ...add 1000h to ES
      mov   es, dx

no_incr_es:   pop   di
      pop    si
      pop   dx
      ret

THANK YOU VERY MUCH IN ADVANCE

I think the problem with the code is at the evaluation of a condition:

jnc read_ok ; jump if no error

Here, you are trying to check for a condition by using the EFLAG register when you haven't got a condition in the first place i.e. cmp eax, 0.

Anyway, this is just a gues.