| 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Int 13h handler that is used to initialize
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| 3 | ; XTIDE Universal BIOS when our INT 19h was not called.
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| 4 |
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| 5 | ;
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| 6 | ; XTIDE Universal BIOS and Associated Tools
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| 7 | ; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
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| 8 | ;
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| 9 | ; This program is free software; you can redistribute it and/or modify
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| 10 | ; it under the terms of the GNU General Public License as published by
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| 11 | ; the Free Software Foundation; either version 2 of the License, or
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| 12 | ; (at your option) any later version.
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| 13 | ;
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| 14 | ; This program is distributed in the hope that it will be useful,
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| 15 | ; but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 16 | ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 17 | ; GNU General Public License for more details.
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| 18 | ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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| 19 | ;
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| 20 |
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| 21 | ; Section containing code
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| 22 | SECTION .text
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| 23 |
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| 24 | TEMPORARY_VECTOR_FOR_SYSTEM_INT13h EQU 20h ; MS-DOS so BIOSes most likely do not use this
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| 25 |
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| 26 |
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| 27 | ;--------------------------------------------------------------------
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| 28 | ; Int 13h software interrupt handler.
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| 29 | ; This handler captures boot sector read from foreign drive when our
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| 30 | ; INT 19h is not called. This way we can for XTIDE Universal BIOS
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| 31 | ; initialization even without INT 19h being called.
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| 32 | ;
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| 33 | ; Int13hBiosInit_Handler
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| 34 | ; Parameters:
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| 35 | ; AH: Bios function
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| 36 | ; READ_SECTORS_INTO_MEMORY will initialize XTIDE Universal BIOS
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| 37 | ;--------------------------------------------------------------------
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| 38 | Int13hBiosInit_Handler:
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| 39 | ; Initialize XTIDE Universal BIOS only if Int13hBiosInit_Handler is still at
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| 40 | ; vector 13h. Otherwise some other BIOS has hooked us and our very late
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| 41 | ; initialization is not possible.
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| 42 | push ds
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| 43 | push ax
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| 44 | LOAD_BDA_SEGMENT_TO ds, ax
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| 45 | pop ax
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| 46 | cmp WORD [BIOS_DISK_INTERRUPT_13h*4], Int13hBiosInit_Handler
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| 47 | pop ds
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| 48 | jne SHORT .VeryLateInitFailed ; XTIDE Universal BIOS does not work
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| 49 |
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| 50 | ; Ignore all but read command (assumed to read boot sector)
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| 51 | cmp ah, READ_SECTORS_INTO_MEMORY
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| 52 | je SHORT Int19h_BootLoaderHandler
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| 53 |
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| 54 | ; Call system INT 13h since not trying to read boot sector
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| 55 | int TEMPORARY_VECTOR_FOR_SYSTEM_INT13h
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| 56 | retf 2
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| 57 |
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| 58 | .VeryLateInitFailed:
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| 59 | mov ah, RET_HD_INVALID
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| 60 | stc
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| 61 | retf 2
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