| [96] | 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Reading and jumping to boot sector.
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| 3 |
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| 4 | ; Section containing code
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| 5 | SECTION .text
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| 6 |
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| 7 | ;--------------------------------------------------------------------
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| 8 | ; BootSector_TryToLoadFromDriveDL
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| 9 | ; Parameters:
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| 10 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 11 | ; DS: RAMVARS segment
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| 12 | ; Returns:
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| 13 | ; ES:BX: Ptr to boot sector (if successfull)
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| 14 | ; CF: Set if boot sector loaded succesfully
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| 15 | ; Cleared if failed to load boot sector
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| 16 | ; Corrupts registers:
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| 17 | ; AX, CX, DH, DI, (DL if failed to read boot sector)
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| 18 | ;--------------------------------------------------------------------
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| 19 | ALIGN JUMP_ALIGN
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| 20 | BootSector_TryToLoadFromDriveDL:
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| 21 | call BootPrint_TryToBootFromDL
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| 22 | call LoadFirstSectorFromDriveDL
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| 23 | jc SHORT .FailedToLoadFirstSector
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| 24 |
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| [128] | 25 | test dl, dl
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| 26 | jns SHORT .AlwaysBootFromFloppyDriveForBooterGames
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| [96] | 27 | cmp WORD [es:bx+510], 0AA55h ; Valid boot sector?
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| 28 | jne SHORT .FirstHardDiskSectorNotBootable
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| 29 | .AlwaysBootFromFloppyDriveForBooterGames:
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| 30 | mov bx, g_szFound
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| 31 | call BootPrint_BootSectorResultStringFromBX
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| 32 | stc
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| 33 | ret
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| 34 | .FailedToLoadFirstSector:
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| 35 | call BootPrint_FailedToLoadFirstSector
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| 36 | clc
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| 37 | ret
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| 38 | .FirstHardDiskSectorNotBootable:
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| 39 | mov bx, g_szNotFound
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| 40 | call BootPrint_BootSectorResultStringFromBX
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| 41 | clc
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| 42 | ret
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| 43 |
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| 44 | ;--------------------------------------------------------------------
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| 45 | ; LoadFirstSectorFromDriveDL
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| 46 | ; Parameters:
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| 47 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 48 | ; Returns:
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| 49 | ; AH: INT 13h error code
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| 50 | ; ES:BX: Ptr to boot sector (if successfull)
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| 51 | ; CF: Cleared if read successfull
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| 52 | ; Set if any error
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| 53 | ; Corrupts registers:
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| 54 | ; AL, CX, DH, DI
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| 55 | ;--------------------------------------------------------------------
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| 56 | ALIGN JUMP_ALIGN
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| 57 | LoadFirstSectorFromDriveDL:
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| 58 | LOAD_BDA_SEGMENT_TO es, bx ; ES:BX now points to...
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| 59 | mov bx, BOOTVARS.rgbBootSect ; ...boot sector location
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| 60 | mov di, BOOT_READ_RETRY_TIMES ; Initialize retry counter
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| 61 | ALIGN JUMP_ALIGN
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| 62 | .ReadRetryLoop:
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| 63 | call .ResetBootDriveFromDL
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| 64 | call .LoadFirstSectorFromDLtoESBX
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| 65 | jnc SHORT .Return
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| 66 | dec di ; Decrement retry counter
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| 67 | jnz SHORT .ReadRetryLoop ; Loop while retries left
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| 68 | ALIGN JUMP_ALIGN
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| 69 | .Return:
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| 70 | ret
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| 71 |
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| 72 | ;--------------------------------------------------------------------
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| 73 | ; .ResetBootDriveFromDL
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| 74 | ; Parameters:
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| 75 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 76 | ; Returns:
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| 77 | ; AH: INT 13h error code
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| 78 | ; CF: Cleared if read successfull
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| 79 | ; Set if any error
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| 80 | ; Corrupts registers:
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| 81 | ; AL
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| 82 | ;--------------------------------------------------------------------
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| 83 | ALIGN JUMP_ALIGN
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| 84 | .ResetBootDriveFromDL:
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| 85 | xor ax, ax ; AH=0h, Disk Controller Reset
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| [128] | 86 | test dl, dl ; Floppy drive?
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| 87 | jns SHORT .SkipAltReset
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| 88 | mov ah, 0Dh ; AH=Dh, Reset Hard Disk (Alternate reset)
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| 89 | .SkipAltReset:
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| [96] | 90 | int INTV_DISK_FUNC
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| 91 | ret
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| 92 |
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| 93 | ;--------------------------------------------------------------------
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| 94 | ; .LoadFirstSectorFromDLtoESBX
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| 95 | ; Parameters:
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| 96 | ; DL: Drive to boot from (translated, 00h or 80h)
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| 97 | ; ES:BX: Destination buffer for boot sector
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| 98 | ; Returns:
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| 99 | ; AH: INT 13h error code
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| 100 | ; ES:BX: Ptr to boot sector
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| 101 | ; CF: Cleared if read successfull
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| 102 | ; Set if any error
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| 103 | ; Corrupts registers:
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| 104 | ; AL, CX, DH
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| 105 | ;--------------------------------------------------------------------
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| 106 | ALIGN JUMP_ALIGN
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| 107 | .LoadFirstSectorFromDLtoESBX:
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| 108 | mov ax, 0201h ; Read 1 sector
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| 109 | mov cx, 1 ; Cylinder 0, Sector 1
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| 110 | xor dh, dh ; Head 0
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| 111 | int INTV_DISK_FUNC
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| 112 | ret
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