[99] | 1 | ; Project name : XTIDE Universal BIOS |
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[3] | 2 | ; Description : Functions for accessing DPT data. |
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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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[150] | 8 | ; AccessDPT_GetDriveSelectByteToAL |
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| 9 | ; Parameters: |
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| 10 | ; DS:DI: Ptr to Disk Parameter Table |
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| 11 | ; Returns: |
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| 12 | ; AL: Drive Select Byte |
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| 13 | ; Corrupts registers: |
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| 14 | ; Nothing |
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| 15 | ;-------------------------------------------------------------------- |
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| 16 | ALIGN JUMP_ALIGN |
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| 17 | AccessDPT_GetDriveSelectByteToAL: |
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| 18 | mov al, [di+DPT.wFlags] |
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| 19 | and al, FLG_DRVNHEAD_LBA | FLG_DRVNHEAD_DRV |
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| 20 | or al, MASK_DRVNHEAD_SET ; Bits set to 1 for old drives |
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| 21 | ret |
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| 22 | |
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| 23 | |
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| 24 | ;-------------------------------------------------------------------- |
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| 25 | ; AccessDPT_GetDeviceControlByteToAL |
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| 26 | ; Parameters: |
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| 27 | ; DS:DI: Ptr to Disk Parameter Table |
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| 28 | ; Returns: |
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| 29 | ; AL: Device Control Byte |
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| 30 | ; Corrupts registers: |
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| 31 | ; Nothing |
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| 32 | ;-------------------------------------------------------------------- |
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| 33 | ALIGN JUMP_ALIGN |
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| 34 | AccessDPT_GetDeviceControlByteToAL: |
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| 35 | xor al, al |
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[158] | 36 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_ENABLE_IRQ |
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[150] | 37 | jnz SHORT .EnableDeviceIrq |
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| 38 | or al, FLG_DEVCONTROL_nIEN ; Disable IRQ |
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| 39 | .EnableDeviceIrq: |
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| 40 | ret |
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| 41 | |
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[193] | 42 | |
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[150] | 43 | ;-------------------------------------------------------------------- |
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[173] | 44 | ; AccessDPT_GetLCHS |
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[3] | 45 | ; Parameters: |
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| 46 | ; DS:DI: Ptr to Disk Parameter Table |
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| 47 | ; Returns: |
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| 48 | ; AX: Number of L-CHS sectors per track |
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| 49 | ; BX: Number of L-CHS cylinders |
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| 50 | ; DX: Number of L-CHS heads |
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| 51 | ; Corrupts registers: |
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[173] | 52 | ; CX |
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[3] | 53 | ;-------------------------------------------------------------------- |
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[173] | 54 | AccessDPT_GetLCHS: |
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| 55 | ; Load CHS from DPT |
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| 56 | eMOVZX ax, BYTE [di+DPT.bSectors] |
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| 57 | mov bx, [di+DPT.dwCylinders] |
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[161] | 58 | cwd |
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[173] | 59 | mov dl, [di+DPT.bHeads] |
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| 60 | |
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| 61 | ; Only need to limit sectors for LBA assist |
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| 62 | test BYTE [di+DPT.bFlagsLow], FLG_DRVNHEAD_LBA |
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[181] | 63 | jz SHORT AccessDPT_ShiftPCHinBXDXtoLCH |
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[173] | 64 | |
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[181] | 65 | cmp WORD [di+DPT.dwCylinders+2], BYTE 0 |
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| 66 | jnz SHORT .Return_MAX_LCHS_CYLINDERS |
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[173] | 67 | |
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[181] | 68 | ; Limit cylinders to 1024 |
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| 69 | cmp bx, MAX_LCHS_CYLINDERS |
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| 70 | jb SHORT .Return |
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| 71 | ALIGN JUMP_ALIGN |
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| 72 | .Return_MAX_LCHS_CYLINDERS: |
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[173] | 73 | mov bx, MAX_LCHS_CYLINDERS |
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[181] | 74 | ALIGN JUMP_ALIGN, ret |
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| 75 | .Return: |
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[3] | 76 | ret |
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| 77 | |
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| 78 | |
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| 79 | ;-------------------------------------------------------------------- |
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[173] | 80 | ; AccessDPT_ShiftPCHinBXDXtoLCH |
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| 81 | ; Parameters: |
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| 82 | ; BX: P-CHS cylinders (1...16383) |
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| 83 | ; DX: P-CHS heads (1...16) |
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| 84 | ; Returns: |
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| 85 | ; BX: Number of L-CHS cylinders (1...1024) |
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| 86 | ; DX: Number of L-CHS heads (1...255) |
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| 87 | ; CX: Number of bits shifted |
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| 88 | ; Corrupts registers: |
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| 89 | ; Nothing |
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| 90 | ;-------------------------------------------------------------------- |
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| 91 | AccessDPT_ShiftPCHinBXDXtoLCH: |
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| 92 | xor cx, cx |
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| 93 | .ShiftLoop: |
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| 94 | cmp bx, MAX_LCHS_CYLINDERS ; Need to shift? |
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| 95 | jbe SHORT .LimitHeadsTo255 ; If not, return |
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| 96 | inc cx ; Increment shift count |
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| 97 | shr bx, 1 ; Halve cylinders |
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| 98 | shl dx, 1 ; Double heads |
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| 99 | jmp SHORT .ShiftLoop |
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| 100 | .LimitHeadsTo255: ; DOS does not support drives with 256 heads |
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[181] | 101 | sub dl, dh ; DH set only when 256 logical heads |
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[173] | 102 | xor dh, dh |
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| 103 | ret |
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| 104 | |
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[193] | 105 | |
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[173] | 106 | ;-------------------------------------------------------------------- |
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[3] | 107 | ; Returns pointer to DRVPARAMS for master or slave drive. |
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| 108 | ; |
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| 109 | ; AccessDPT_GetPointerToDRVPARAMStoCSBX |
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| 110 | ; Parameters: |
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| 111 | ; DS:DI: Ptr to Disk Parameter Table |
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| 112 | ; Returns: |
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| 113 | ; CS:BX: Ptr to DRVPARAMS |
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| 114 | ; Corrupts registers: |
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| 115 | ; Nothing |
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| 116 | ;-------------------------------------------------------------------- |
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| 117 | ALIGN JUMP_ALIGN |
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| 118 | AccessDPT_GetPointerToDRVPARAMStoCSBX: |
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[150] | 119 | eMOVZX bx, [di+DPT.bIdevarsOffset] ; CS:BX points to IDEVARS |
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| 120 | add bx, BYTE IDEVARS.drvParamsMaster ; CS:BX points to Master Drive DRVPARAMS |
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[158] | 121 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_SLAVE |
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[150] | 122 | jz SHORT .ReturnPointerToDRVPARAMS |
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| 123 | add bx, BYTE DRVPARAMS_size ; CS:BX points to Slave Drive DRVPARAMS |
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| 124 | .ReturnPointerToDRVPARAMS: |
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[3] | 125 | ret |
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[200] | 126 | |
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| 127 | ;-------------------------------------------------------------------- |
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| 128 | ; AccessDPT_GetUnshiftedAddressModeToALZF |
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| 129 | ; Parameters: |
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| 130 | ; DS:DI: Ptr to Disk Parameter Table |
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| 131 | ; Returns: |
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| 132 | ; AL: Addressing Mode (L-CHS, P-CHS, LBA28, LBA48) |
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| 133 | ; unshifted (still shifted where it is in bFlagsLow) |
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| 134 | ; ZF: Set based on value in AL |
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| 135 | ; Corrupts registers: |
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| 136 | ; AL |
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| 137 | ;-------------------------------------------------------------------- |
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| 138 | ; |
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| 139 | ; Converted to a macro since only called in two places, and the call/ret overhead |
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| 140 | ; is not worth it for these two instructions (4 bytes total) |
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| 141 | ; |
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| 142 | %macro AccessDPT_GetUnshiftedAddressModeToALZF 0 |
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| 143 | mov al, [di+DPT.bFlagsLow] |
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| 144 | and al, MASKL_DPT_ADDRESSING_MODE |
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| 145 | %endmacro |
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| 146 | |
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| 147 | |
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