| 1 | ; File name : Int19h.asm
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| 2 | ; Project name : IDE BIOS
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| 3 | ; Created date : 3.8.2007
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| 4 | ; Last update : 28.11.2010
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| 5 | ; Author : Tomi Tilli
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| 6 | ; Description : Int 19h BIOS functions (Boot Strap Loader).
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| 7 |
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| 8 | ; Section containing code
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| 9 | SECTION .text
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| 10 |
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| 11 | B_READ_RETRY_TIMES EQU 3 ; Number of times to retry
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| 12 |
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| 13 |
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| 14 | ;--------------------------------------------------------------------
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| 15 | ; Int 19h software interrupt handler for late initialization.
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| 16 | ; Calls actual Int 19h after initialization is complete.
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| 17 | ;
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| 18 | ; Int19h_LateInitialization
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| 19 | ; Parameters:
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| 20 | ; Nothing
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| 21 | ; Returns:
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| 22 | ; Never returns
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| 23 | ;--------------------------------------------------------------------
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| 24 | ALIGN JUMP_ALIGN
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| 25 | Int19h_LateInitialization:
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| 26 | call Initialize_ShouldSkip ; Skip initialization?
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| 27 | jc SHORT .SkipInitialization
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| 28 | call Initialize_AndDetectDrives
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| 29 | int INTV_BOOTSTRAP ; Call actual boot loader
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| 30 | .SkipInitialization:
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| 31 | call RamVars_Initialize ; RAMVARS must be initialized even for simple boot loader
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| 32 | ; Fall to Int19h_SimpleBootLoader
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| 33 |
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| 34 | ;--------------------------------------------------------------------
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| 35 | ; Simple boot loader.
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| 36 | ; Boot sequence is fixed to 00h, 80h and INT 18h.
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| 37 | ;
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| 38 | ; Int19h_SimpleBootLoader
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| 39 | ; Parameters:
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| 40 | ; Nothing
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| 41 | ; Returns:
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| 42 | ; Never returns
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| 43 | ;--------------------------------------------------------------------
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| 44 | ALIGN JUMP_ALIGN
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| 45 | Int19h_SimpleBootLoader:
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| 46 | sti ; Enable interrupts
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| 47 | call RamVars_GetSegmentToDS
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| 48 | xor dx, dx
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| 49 | call Int19h_TryToLoadBootSectorFromDL
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| 50 | jc SHORT Int19h_JumpToBootSector
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| 51 | mov dl, 80h
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| 52 | call Int19h_TryToLoadBootSectorFromDL
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| 53 | jc SHORT Int19h_JumpToBootSector
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| 54 | call Int19h_BootFailure ; Should never return
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| 55 | jmp SHORT Int19h_SimpleBootLoader
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| 56 |
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| 57 | ;--------------------------------------------------------------------
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| 58 | ; Boots if boot sector is successfully read from the drive.
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| 59 | ;
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| 60 | ; Int19h_TryToLoadBootSectorFromDL
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| 61 | ; Parameters:
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| 62 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 63 | ; DS: RAMVARS segment
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| 64 | ; Returns:
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| 65 | ; ES:BX: Ptr to boot sector (if successfull)
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| 66 | ; CF: Set if boot sector loaded succesfully
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| 67 | ; Cleared if failed to load boot sector
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| 68 | ; Corrupts registers:
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| 69 | ; AX, CX, DH, DI, (DL if failed to read boot sector)
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| 70 | ;--------------------------------------------------------------------
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| 71 | ALIGN JUMP_ALIGN
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| 72 | Int19h_TryToLoadBootSectorFromDL:
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| 73 | call BootPrint_TryToBootFromDL
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| 74 | call Int19h_LoadFirstSectorFromDL
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| 75 | jc SHORT .FailedToLoadFirstSector
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| 76 |
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| 77 | test dl, 80h
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| 78 | jz SHORT .AlwaysBootFromFloppyDriveForBooterGames
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| 79 | cmp WORD [es:bx+510], 0AA55h ; Valid boot sector?
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| 80 | jne SHORT .FirstHardDiskSectorNotBootable
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| 81 | .AlwaysBootFromFloppyDriveForBooterGames:
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| 82 | call BootPrint_BootSectorLoaded
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| 83 | stc
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| 84 | ret
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| 85 | .FailedToLoadFirstSector:
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| 86 | call BootPrint_FailedToLoadFirstSector
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| 87 | clc
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| 88 | ret
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| 89 | .FirstHardDiskSectorNotBootable:
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| 90 | call BootPrint_FirstSectorNotBootable
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| 91 | clc
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| 92 | ret
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| 93 |
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| 94 | ;--------------------------------------------------------------------
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| 95 | ; Reads first sector (boot sector) from drive DL.
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| 96 | ;
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| 97 | ; Int19h_LoadFirstSectorFromDL
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| 98 | ; Parameters:
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| 99 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 100 | ; Returns:
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| 101 | ; AH: INT 13h error code
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| 102 | ; ES:BX: Ptr to boot sector (if successfull)
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| 103 | ; CF: Cleared if read successfull
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| 104 | ; Set if any error
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| 105 | ; Corrupts registers:
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| 106 | ; AL, CX, DH, DI
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| 107 | ;--------------------------------------------------------------------
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| 108 | ALIGN JUMP_ALIGN
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| 109 | Int19h_LoadFirstSectorFromDL:
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| 110 | LOAD_BDA_SEGMENT_TO es, bx ; ES:BX now points to...
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| 111 | mov bx, BOOTVARS.rgbBootSect ; ...boot sector location
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| 112 | mov di, B_READ_RETRY_TIMES ; Retry counter
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| 113 | ALIGN JUMP_ALIGN
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| 114 | .ReadRetryLoop:
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| 115 | call .ResetBootDriveFromDL
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| 116 | call .LoadFirstSectorFromDLtoESBX
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| 117 | jnc SHORT .Return
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| 118 | dec di ; Decrement retry counter
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| 119 | jnz SHORT .ReadRetryLoop ; Loop while retries left
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| 120 | stc
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| 121 | ALIGN JUMP_ALIGN
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| 122 | .Return:
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| 123 | ret
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| 124 |
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| 125 | ;--------------------------------------------------------------------
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| 126 | ; .ResetBootDriveFromDL
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| 127 | ; Parameters:
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| 128 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 129 | ; Returns:
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| 130 | ; AH: INT 13h error code
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| 131 | ; CF: Cleared if read successfull
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| 132 | ; Set if any error
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| 133 | ; Corrupts registers:
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| 134 | ; AL
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| 135 | ;--------------------------------------------------------------------
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| 136 | ALIGN JUMP_ALIGN
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| 137 | .ResetBootDriveFromDL:
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| 138 | xor ax, ax ; AH=0h, Disk Controller Reset
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| 139 | test dl, 80h ; Floppy drive?
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| 140 | jz SHORT .ResetDriveFromDL ; If so, jump to reset
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| 141 | mov ah, 0Dh ; AH=Dh, Reset Hard Disk (Alternate reset)
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| 142 | .ResetDriveFromDL:
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| 143 | int INTV_DISK_FUNC
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| 144 | ret
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| 145 |
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| 146 | ;--------------------------------------------------------------------
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| 147 | ; Reads first sector (boot sector) from drive DL to ES:BX.
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| 148 | ;
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| 149 | ; .LoadFirstSectorFromDLtoESBX
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| 150 | ; Parameters:
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| 151 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 152 | ; ES:BX: Destination buffer for boot sector
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| 153 | ; Returns:
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| 154 | ; AH: INT 13h error code
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| 155 | ; ES:BX: Ptr to boot sector
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| 156 | ; CF: Cleared if read successfull
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| 157 | ; Set if any error
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| 158 | ; Corrupts registers:
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| 159 | ; AL, CX, DH
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| 160 | ;--------------------------------------------------------------------
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| 161 | ALIGN JUMP_ALIGN
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| 162 | .LoadFirstSectorFromDLtoESBX:
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| 163 | mov ax, 0201h ; Read 1 sector
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| 164 | mov cx, 1 ; Cylinder 0, Sector 1
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| 165 | xor dh, dh ; Head 0
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| 166 | int INTV_DISK_FUNC
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| 167 | ret
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| 168 |
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| 169 |
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| 170 | ;--------------------------------------------------------------------
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| 171 | ; Jumps to boot sector pointed by ES:BX.
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| 172 | ;
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| 173 | ; Int19h_JumpToBootSector
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| 174 | ; Parameters:
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| 175 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 176 | ; ES:BX: Ptr to boot sector
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| 177 | ; Returns:
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| 178 | ; Never returns
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| 179 | ;--------------------------------------------------------------------
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| 180 | ALIGN JUMP_ALIGN
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| 181 | Int19h_JumpToBootSector:
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| 182 | push es ; Push boot sector segment
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| 183 | push bx ; Push boot sector offset
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| 184 | call Int19h_ClearSegmentsForBoot
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| 185 | xor dh, dh ; Device supported by INT 13h
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| 186 | retf
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| 187 |
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| 188 | ;--------------------------------------------------------------------
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| 189 | ; Clears DS and ES registers to zero.
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| 190 | ;
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| 191 | ; Int19h_ClearSegmentsForBoot
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| 192 | ; Parameters:
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| 193 | ; Nothing
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| 194 | ; Returns:
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| 195 | ; DS=ES: Zero
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| 196 | ; Corrupts registers:
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| 197 | ; AX
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| 198 | ;--------------------------------------------------------------------
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| 199 | ALIGN JUMP_ALIGN
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| 200 | Int19h_ClearSegmentsForBoot:
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| 201 | xor ax, ax
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| 202 | mov ds, ax
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| 203 | mov es, ax
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| 204 | ret
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| 205 |
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| 206 |
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| 207 | ;--------------------------------------------------------------------
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| 208 | ; Calls INT 18h (ROM Basic or Boot Failure). Called after booting from
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| 209 | ; floppy drive or hard disk fails.
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| 210 | ;
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| 211 | ; Int19h_BootFailure
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| 212 | ; Parameters:
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| 213 | ; Nothing
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| 214 | ; Returns:
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| 215 | ; Should never return (but might)
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| 216 | ;--------------------------------------------------------------------
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| 217 | ALIGN JUMP_ALIGN
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| 218 | Int19h_BootFailure:
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| 219 | call Int19h_ClearSegmentsForBoot
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| 220 | int INTV_BOOT_FAILURE
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| 221 | ret
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