source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13h/Tools/Address.asm@ 590

; Project name  :   XTIDE Universal BIOS
; Description   :   Functions for address translations.

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 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

;---------------------------------------------------------------------
; Address_ExtractLCHSparametersFromOldInt13hAddress
;   Parameters:
;       CH:     Cylinder number, bits 7...0
;       CL:     Bits 7...6: Cylinder number bits 9 and 8
;               Bits 5...0: Sector number
;       DH:     Head number
;   Returns:
;       BL:     Sector number (1...63)
;       BH:     Head number (0...255)
;       CX:     Cylinder number (0...1023)
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Address_ExtractLCHSparametersFromOldInt13hAddress:
    mov     bl, 3Fh             ; Load sector number mask
    and     bl, cl              ; Sector number now in BL
    sub     cl, bl              ; Remove from cylinder number high
    eROL_IM cl, 2               ; High bits to beginning
    mov     bh, dh              ; Copy Head number
    xchg    cl, ch              ; Cylinder number now in CX
    ret


;---------------------------------------------------------------------
; Converts LARGE addressing mode LCHS parameters to IDE P-CHS parameters.
; PCylinder = (LCylinder << n) + (LHead / PHeadCount)
; PHead     = LHead % PHeadCount
; PSector   = LSector
;
; ConvertLargeModeLCHStoPCHS:
;   Parameters:
;       BL:     Sector number (1...63)
;       BH:     Head number (0...239)
;       CX:     Cylinder number (0...1023)
;       DS:DI:  Ptr to Disk Parameter Table
;   Returns:
;       BL:     Sector number (1...63)
;       BH:     Head number (0...15)
;       CX:     Cylinder number (0...16382)
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
ConvertLargeModeLCHStoPCHS:
    ; LHead / PHeadCount and LHead % PHeadCount
    eMOVZX  ax, bh                  ; Copy L-CHS Head number to AX
    div     BYTE [di+DPT.bPchsHeads]; AL = LHead / PHeadCount, AH = LHead % PHeadCount
    mov     bh, ah                  ; Copy P-CHS Head number to BH
    xor     ah, ah                  ; AX = LHead / PHeadCount

    ; (LCylinder << n) + (LHead / PHeadCount)
    mov     dx, cx                  ; Copy L-CHS Cylinder number to DX
    mov     cl, MASKL_DPT_CHS_SHIFT_COUNT   ; Load shift count mask
    and     cl, [di+DPT.bFlagsLow]  ; Shift count now in CL
    shl     dx, cl                  ; DX = LCylinder << n
    add     ax, dx                  ; AX = P-CHS Cylinder number
    xchg    cx, ax                  ; Move P-CHS Cylinder number to CX
DoNotConvertLCHS:
    ret

; *FIXME* The above function description doesn't match the code.
; If CX has a maximum value of 1023 on entry then there is no way CX can be 16382 on return.
; 1023 SHL 3 (MASKL_DPT_CHS_SHIFT_COUNT) is 8184. With the addition of AX (at most 255?)
; the result is 8439.

;--------------------------------------------------------------------
; Address_OldInt13hAddressToIdeAddress
;   Parameters:
;       CH:     Cylinder number, bits 7...0
;       CL:     Bits 7...6: Cylinder number bits 9 and 8
;               Bits 5...0: Starting sector number (1...63)
;       DH:     Starting head number (0...255)
;       DS:DI:  Ptr to DPT
;   Returns:
;       BL:     LBA Low Register / Sector Number Register (LBA 7...0)
;       CL:     LBA Mid Register / Low Cylinder Register (LBA 15...8)
;       CH:     LBA High Register / High Cylinder Register (LBA 23...16)
;       BH:     Drive and Head Register (LBA 27...24)
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Address_OldInt13hAddressToIdeAddress:
    call    Address_ExtractLCHSparametersFromOldInt13hAddress
    mov     al, [di+DPT.bFlagsLow]
    and     al, MASKL_DPT_TRANSLATEMODE

;;; 0: ADDRESSING_MODE_NORMAL
    jz      SHORT DoNotConvertLCHS

;;; 1: ADDRESSING_MODE_LARGE
    test    al, FLGL_DPT_ASSISTED_LBA
    jz      SHORT ConvertLargeModeLCHStoPCHS

;;; 2: ADDRESSING_MODE_ASSISTED_LBA
    ; Fall to ConvertAssistedLBAModeLCHStoLBARegisterValues


;---------------------------------------------------------------------
; Converts LCHS parameters to 28-bit LBA address.
; Only 24-bits are used since LHCS to LBA28 conversion has 8.4GB limit.
; LBA = ((cylToSeek*headsPerCyl+headToSeek)*sectPerTrack)+sectToSeek-1
; headsPerCyl and sectPerTrack are the current translation values (L-CHS).
;
; Returned address is in same registers that
; DoNotConvertLCHS and ConvertLargeModeLCHStoPCHS returns.
;
; ConvertAssistedLBAModeLCHStoLBARegisterValues:
;   Parameters:
;       BL:     Sector number (1...63)
;       BH:     Head number (0...254)
;       CX:     Cylinder number (0...1023)
;       DS:DI:  Ptr to Disk Parameter Table
;   Returns:
;       BL:     LBA Low Register / Sector Number Register (LBA 7...0)
;       CL:     LBA Mid Register / Low Cylinder Register (LBA 15...8)
;       CH:     LBA High Register / High Cylinder Register (LBA 23...16)
;       BH:     Drive and Head Register (LBA 27...24)
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
ConvertAssistedLBAModeLCHStoLBARegisterValues:
    ; cylToSeek*headsPerCyl (18-bit result)
    ; Max = 1023 * 255 = 260,865 = 3FB01h
    mov     ax, LBA_ASSIST_SPT      ; Load Sectors per Track
    xchg    cx, ax                  ; Cylinder number to AX, Sectors per Track to CX
%ifdef USE_386
    movzx   dx, [di+DPT.bLchsHeads]
%else
    cwd
    mov     dl, [di+DPT.bLchsHeads]
%endif
    mul     dx                      ; DX:AX = cylToSeek*headsPerCyl

    ; +=headToSeek (18-bit result)
    ; Max = 260,865 + 254 = 261,119 = 3FBFFh
    add     al, bh                  ; Add Head number to DX:AX
    adc     ah, dh                  ; DH = Zero after previous multiplication
    adc     dl, dh

    ; *=sectPerTrack (18-bit by 6-bit multiplication with 24-bit result)
    ; Max = 261,119 * 63 = 16,450,497 = FB03C1h
    xchg    ax, dx                  ; Hiword to AX, loword to DX
    mul     cl                      ; AX = hiword * Sectors per Track
    mov     bh, al                  ; Backup hiword * Sectors per Track
    xchg    ax, dx                  ; Loword back to AX
    mul     cx                      ; DX:AX = loword * Sectors per Track
    add     dl, bh                  ; DX:AX = (cylToSeek*headsPerCyl+headToSeek)*sectPerTrack

    ; +=sectToSeek-1 (24-bit result)
    ; Max = 16,450,497 + 63 - 1 = 16,450,559 = FB03FFh
    mov     bh, ch                  ; Sector number now in BX, CH=zero
    dec     bx                      ; sectToSeek-=1
    add     bx, ax                  ; Add loword to BX (BL = Sector Number Register (LBA 7...0))
    adc     ch, dl                  ; Add possible carry to byte2 (CH = High Cylinder Register (LBA 23...16))
    mov     cl, bh                  ; CL = Low Cylinder Register (LBA 15...8)
    mov     bh, dh                  ; BH = Drive and Head Register (LBA 27...24)
    ret