source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Device/IDE/IdeIO.asm@ 390

; Project name  :   XTIDE Universal BIOS
; Description   :   IDE Register I/O functions.

;
; XTIDE Universal BIOS and Associated Tools 
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
; 
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.      
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;       

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; IdeIO_OutputALtoIdeControlBlockRegisterInDL
; IdeIO_OutputALtoIdeRegisterInDL
;   Parameters:
;       AL:     Byte to output
;       DL:     IDE Control Block Register  (IdeIO_OutputALtoIdeControlBlockRegisterInDL)
;               IDE Register                (IdeIO_OutputALtoIdeRegisterInDL)
;       DS:DI:  Ptr to DPT (in RAMVARS segment)
;   Returns:
;       Nothing
;   Corrupts registers:
;       BX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
IdeIO_OutputALtoIdeControlBlockRegisterInDL:
    mov     bl, IDEVARS.wPortCtrl
    SKIP2B  f   ; cmp ax, <next instruction>
    ; Fall to IdeIO_OutputALtoIdeRegisterInDL

IdeIO_OutputALtoIdeRegisterInDL:
    mov     bl, IDEVARS.wPort
    call    GetPortToDXandTranslateA0andA3ifNecessary
    out     dx, al
    ret


;--------------------------------------------------------------------
; IdeIO_InputToALfromIdeRegisterInDL
;   Parameters:
;       DL:     IDE Register
;       DS:DI:  Ptr to DPT (in RAMVARS segment)
;   Returns:
;       AL:     Inputted byte
;   Corrupts registers:
;       BX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
IdeIO_InputToALfromIdeRegisterInDL:
    mov     bl, IDEVARS.wPort
    call    GetPortToDXandTranslateA0andA3ifNecessary
    in      al, dx
    ret


;--------------------------------------------------------------------
; GetPortToDXandTranslateA0andA3ifNecessary
;   Parameters:
;       BL:     Offset to port in IDEVARS (IDEVARS.wPort or IDEVARS.wPortCtrl)
;       DL:     IDE Register
;       DS:DI:  Ptr to DPT (in RAMVARS segment)
;   Returns:
;       DX:     Source/Destination Port
;   Corrupts registers:
;       BX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
GetPortToDXandTranslateA0andA3ifNecessary:
    xor     bh, bh
    add     bl, [di+DPT.bIdevarsOffset]     ; CS:BX now points port address
    xor     dh, dh                          ; DX now has IDE register offset
    add     dx, [cs:bx]
    test    BYTE [di+DPT.bFlagsHigh], FLGH_DPT_REVERSED_A0_AND_A3
    jz      SHORT .ReturnPortInDX

    ; Exchange address lines A0 and A3 from DL
    mov     bl, dl
    mov     bh, MASK_A3_AND_A0_ADDRESS_LINES
    and     bh, bl                          ; BH = 0, 1, 8 or 9, we can ignore 0 and 9
    jz      SHORT .ReturnPortInDX           ; Jump out since DH is 0
    xor     bh, MASK_A3_AND_A0_ADDRESS_LINES
    jz      SHORT .ReturnPortInDX           ; Jump out since DH was 9
    and     dl, ~MASK_A3_AND_A0_ADDRESS_LINES
    or      dl, bh                          ; Address lines now reversed
.ReturnPortInDX:
    ret