[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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[130] | 30 | mov ax, g_szFound |
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| 31 | call BootPrint_BootSectorResultStringFromAX |
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[96] | 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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[130] | 39 | mov ax, g_szNotFound |
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| 40 | call BootPrint_BootSectorResultStringFromAX |
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[96] | 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 | .Return: |
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| 69 | ret |
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| 70 | |
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| 71 | ;-------------------------------------------------------------------- |
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| 72 | ; .ResetBootDriveFromDL |
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| 73 | ; Parameters: |
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| 74 | ; DL: Drive to boot from (translated, 00h or 80h) |
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| 75 | ; Returns: |
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| 76 | ; AH: INT 13h error code |
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| 77 | ; CF: Cleared if read successfull |
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| 78 | ; Set if any error |
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| 79 | ; Corrupts registers: |
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| 80 | ; AL |
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| 81 | ;-------------------------------------------------------------------- |
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| 82 | ALIGN JUMP_ALIGN |
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| 83 | .ResetBootDriveFromDL: |
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| 84 | xor ax, ax ; AH=0h, Disk Controller Reset |
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[128] | 85 | test dl, dl ; Floppy drive? |
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| 86 | jns SHORT .SkipAltReset |
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| 87 | mov ah, 0Dh ; AH=Dh, Reset Hard Disk (Alternate reset) |
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| 88 | .SkipAltReset: |
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[96] | 89 | int INTV_DISK_FUNC |
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| 90 | ret |
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| 91 | |
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| 92 | ;-------------------------------------------------------------------- |
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| 93 | ; .LoadFirstSectorFromDLtoESBX |
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| 94 | ; Parameters: |
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| 95 | ; DL: Drive to boot from (translated, 00h or 80h) |
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| 96 | ; ES:BX: Destination buffer for boot sector |
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| 97 | ; Returns: |
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| 98 | ; AH: INT 13h error code |
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| 99 | ; ES:BX: Ptr to boot sector |
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| 100 | ; CF: Cleared if read successfull |
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| 101 | ; Set if any error |
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| 102 | ; Corrupts registers: |
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| 103 | ; AL, CX, DH |
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| 104 | ;-------------------------------------------------------------------- |
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| 105 | ALIGN JUMP_ALIGN |
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| 106 | .LoadFirstSectorFromDLtoESBX: |
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| 107 | mov ax, 0201h ; Read 1 sector |
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| 108 | mov cx, 1 ; Cylinder 0, Sector 1 |
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| 109 | xor dh, dh ; Head 0 |
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| 110 | int INTV_DISK_FUNC |
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| 111 | ret |
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