| 1 | ; Project name : XTIDE Universal BIOS
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| 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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| 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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| 36 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_ENABLE_IRQ
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| 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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| 42 |
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| 43 | ;--------------------------------------------------------------------
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| 44 | ; AccessDPT_GetAddressingModeForWordLookToBX
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| 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 | ; BX: Addressing Mode (L-CHS, P-CHS, LBA28, LBA48) shifted for WORD lookup
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| 49 | ; Corrupts registers:
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| 50 | ; Nothing
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| 51 | ;--------------------------------------------------------------------
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| 52 | ALIGN JUMP_ALIGN
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| 53 | AccessDPT_GetAddressingModeForWordLookToBX:
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| 54 | mov bl, [di+DPT.bFlagsLow]
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| 55 | and bx, BYTE MASKL_DPT_ADDRESSING_MODE
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| 56 | eSHR_IM bx, ADDRESSING_MODE_FIELD_POSITION-1
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| 57 | ret
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| 58 |
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| 59 |
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| 60 | ;--------------------------------------------------------------------
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| 61 | ; AccessDPT_GetLCHS
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| 62 | ; Parameters:
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| 63 | ; DS:DI: Ptr to Disk Parameter Table
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| 64 | ; Returns:
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| 65 | ; AX: Number of L-CHS sectors per track
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| 66 | ; BX: Number of L-CHS cylinders
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| 67 | ; DX: Number of L-CHS heads
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| 68 | ; Corrupts registers:
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| 69 | ; CX
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| 70 | ;--------------------------------------------------------------------
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| 71 | AccessDPT_GetLCHS:
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| 72 | ; Load CHS from DPT
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| 73 | eMOVZX ax, BYTE [di+DPT.bSectors]
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| 74 | mov bx, [di+DPT.dwCylinders]
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| 75 | cwd
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| 76 | mov dl, [di+DPT.bHeads]
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| 77 |
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| 78 | ; Only need to limit sectors for LBA assist
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| 79 | test BYTE [di+DPT.bFlagsLow], FLG_DRVNHEAD_LBA
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| 80 | jnz SHORT .ReturnLbaAssistedLCHS
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| 81 |
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| 82 | ; P-CHS to L-CHS translation when necessary
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| 83 | jmp SHORT AccessDPT_ShiftPCHinBXDXtoLCH
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| 84 |
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| 85 | .ReturnLbaAssistedLCHS:
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| 86 | cmp WORD [di+DPT.dwCylinders+2], BYTE 0
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| 87 | jz SHORT .LimitCylindersTo1024
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| 88 | mov bx, MAX_LCHS_CYLINDERS
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| 89 | .LimitCylindersTo1024:
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| 90 | MIN_U bx, MAX_LCHS_CYLINDERS
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| 91 | ret
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| 92 |
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| 93 |
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| 94 | ;--------------------------------------------------------------------
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| 95 | ; AccessDPT_ShiftPCHinBXDXtoLCH
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| 96 | ; Parameters:
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| 97 | ; BX: P-CHS cylinders (1...16383)
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| 98 | ; DX: P-CHS heads (1...16)
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| 99 | ; Returns:
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| 100 | ; BX: Number of L-CHS cylinders (1...1024)
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| 101 | ; DX: Number of L-CHS heads (1...255)
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| 102 | ; CX: Number of bits shifted
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| 103 | ; Corrupts registers:
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| 104 | ; Nothing
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| 105 | ;--------------------------------------------------------------------
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| 106 | AccessDPT_ShiftPCHinBXDXtoLCH:
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| 107 | xor cx, cx
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| 108 | .ShiftLoop:
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| 109 | cmp bx, MAX_LCHS_CYLINDERS ; Need to shift?
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| 110 | jbe SHORT .LimitHeadsTo255 ; If not, return
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| 111 | inc cx ; Increment shift count
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| 112 | shr bx, 1 ; Halve cylinders
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| 113 | shl dx, 1 ; Double heads
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| 114 | jmp SHORT .ShiftLoop
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| 115 | .LimitHeadsTo255: ; DOS does not support drives with 256 heads
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| 116 | sub dl, dh ; BH set only when 256 logical heads
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| 117 | xor dh, dh
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| 118 | ret
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| 119 |
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| 120 |
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| 121 | ;--------------------------------------------------------------------
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| 122 | ; AccessDPT_TestIdeVarsFlagsForMasterOrSlaveDrive
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| 123 | ; Parameters:
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| 124 | ; AX: Bitmask to test DRVPARAMS.wFlags
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| 125 | ; DS:DI: Ptr to Disk Parameter Table
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| 126 | ; Returns:
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| 127 | ; ZF: Set if tested bit was zero
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| 128 | ; Cleared if tested bit was non-zero
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| 129 | ; CF: 0
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| 130 | ; Corrupts registers:
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| 131 | ; BX
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| 132 | ;--------------------------------------------------------------------
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| 133 | ALIGN JUMP_ALIGN
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| 134 | AccessDPT_TestIdeVarsFlagsForMasterOrSlaveDrive:
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| 135 | call AccessDPT_GetPointerToDRVPARAMStoCSBX
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| 136 | test [cs:bx+DRVPARAMS.wFlags], ax
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| 137 | ret
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| 138 |
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| 139 | ;--------------------------------------------------------------------
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| 140 | ; Returns pointer to DRVPARAMS for master or slave drive.
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| 141 | ;
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| 142 | ; AccessDPT_GetPointerToDRVPARAMStoCSBX
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| 143 | ; Parameters:
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| 144 | ; DS:DI: Ptr to Disk Parameter Table
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| 145 | ; Returns:
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| 146 | ; CS:BX: Ptr to DRVPARAMS
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| 147 | ; Corrupts registers:
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| 148 | ; Nothing
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| 149 | ;--------------------------------------------------------------------
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| 150 | ALIGN JUMP_ALIGN
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| 151 | AccessDPT_GetPointerToDRVPARAMStoCSBX:
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| 152 | eMOVZX bx, [di+DPT.bIdevarsOffset] ; CS:BX points to IDEVARS
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| 153 | add bx, BYTE IDEVARS.drvParamsMaster ; CS:BX points to Master Drive DRVPARAMS
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| 154 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_SLAVE
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| 155 | jz SHORT .ReturnPointerToDRVPARAMS
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| 156 | add bx, BYTE DRVPARAMS_size ; CS:BX points to Slave Drive DRVPARAMS
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| 157 | .ReturnPointerToDRVPARAMS:
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| 158 | ret
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