| 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_GetLCHS
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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 | ; 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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| 52 | ; CX
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| 53 | ;--------------------------------------------------------------------
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| 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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| 58 | cwd
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| 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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| 63 | jz SHORT AccessDPT_ShiftPCHinBXDXtoLCH
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| 64 |
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| 65 | cmp WORD [di+DPT.dwCylinders+2], BYTE 0
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| 66 | jnz SHORT .Return_MAX_LCHS_CYLINDERS
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| 67 |
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| 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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| 73 | mov bx, MAX_LCHS_CYLINDERS
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| 74 | ALIGN JUMP_ALIGN, ret
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| 75 | .Return:
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| 76 | ret
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| 77 |
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| 78 |
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| 79 | ;--------------------------------------------------------------------
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| 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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| 101 | sub dl, dh ; DH set only when 256 logical heads
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| 102 | xor dh, dh
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| 103 | ret
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| 104 |
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| 105 |
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| 106 | ;--------------------------------------------------------------------
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| 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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| 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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| 121 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_SLAVE
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| 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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| 125 | ret
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