source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13h/Tools/Address.asm@ 193

Last change on this file since 193 was 193, checked in by gregli@…, 13 years ago

Space optimizations in AccessDPT.asm, transfer one routine to a macro (retaining some encapsulation), and transfer the unique part of another routine to the one place it was being called (which also makes what it was doing more transparent).
File size: 5.6 KB
Line 
1; Project name : XTIDE Universal BIOS
2; Description : Functions for address translations.
3
4; Section containing code
5SECTION .text
6
7;---------------------------------------------------------------------
8; Address_ExtractLCHSparametersFromOldInt13hAddress
9; Parameters:
10; CH: Cylinder number, bits 7...0
11; CL: Bits 7...6: Cylinder number bits 9 and 8
12; Bits 5...0: Sector number
13; DH: Head number
14; Returns:
15; BL: Sector number (1...63)
16; BH: Head number (0...255)
17; CX: Cylinder number (0...1023)
18; Corrupts registers:
19; Nothing
20;--------------------------------------------------------------------
21ALIGN JUMP_ALIGN
22Address_ExtractLCHSparametersFromOldInt13hAddress:
23 mov bl, cl ; Copy sector number...
24 and bl, 3Fh ; ...and limit to 1...63
25 sub cl, bl ; Remove from cylinder number high
26 eROL_IM cl, 2 ; High bits to beginning
27 mov bh, dh ; Copy Head number
28 xchg cl, ch ; Cylinder number now in CX
29 ret
30
31
32;---------------------------------------------------------------------
33; Converts LCHS parameters to IDE P-CHS parameters.
34; PCylinder = (LCylinder << n) + (LHead / PHeadCount)
35; PHead = LHead % PHeadCount
36; PSector = LSector
37;
38; Address_ConvertLCHStoPCHS:
39; Parameters:
40; BL: Sector number (1...63)
41; BH: Head number (0...255)
42; CX: Cylinder number (0...1023)
43; DS:DI: Ptr to Disk Parameter Table
44; Returns:
45; BL: Sector number (1...63)
46; BH: Head number (0...15)
47; CX: Cylinder number (0...16382)
48; Corrupts registers:
49; AX, DX
50;--------------------------------------------------------------------
51ALIGN JUMP_ALIGN
52ConvertLCHStoPCHS:
53 ; LHead / PHeadCount and LHead % PHeadCount
54 eMOVZX ax, bh ; Copy L-CHS Head number to AX
55 div BYTE [di+DPT.bHeads] ; AL = LHead / PHeadCount, AH = LHead % PHeadCount
56 mov bh, ah ; Copy P-CHS Head number to BH
57 xor ah, ah ; AX = LHead / PHeadCount
58
59 ; (LCylinder << n) + (LHead / PHeadCount)
60 mov dx, cx ; Copy L-CHS Cylinder number to DX
61 mov cl, [di+DPT.bFlagsLow] ; Load shift count
62 and cl, MASKL_DPT_CHS_SHIFT_COUNT
63 shl dx, cl ; DX = LCylinder << n
64 add ax, dx ; AX = P-CHS Cylinder number
65 xchg cx, ax ; Move P-CHS Cylinder number to CX
66DoNotConvertLCHS:
67 ret
68
69;--------------------------------------------------------------------
70; Address_OldInt13hAddressToIdeAddress
71; Parameters:
72; CH: Cylinder number, bits 7...0
73; CL: Bits 7...6: Cylinder number bits 9 and 8
74; Bits 5...0: Starting sector number (1...63)
75; DH: Starting head number (0...255)
76; DS:DI: Ptr to DPT
77; Returns:
78; BL: LBA Low Register / Sector Number Register (LBA 7...0)
79; CL: LBA Mid Register / Low Cylinder Register (LBA 15...8)
80; CH: LBA High Register / High Cylinder Register (LBA 23...16)
81; BH: Drive and Head Register (LBA 27...24)
82; Corrupts registers:
83; AX, DX
84;--------------------------------------------------------------------
85ALIGN JUMP_ALIGN
86Address_OldInt13hAddressToIdeAddress:
87 call Address_ExtractLCHSparametersFromOldInt13hAddress
88
89 CustomDPT_GetUnshiftedAddressModeToALZF
90 jz DoNotConvertLCHS ; 0, ADDR_DPT_LCHS
91
92 ;;
93 ;; Since we are only checking for zero, we can do our math in the high order bits,
94 ;; in this case effectively subtracting 1 from the address mode.
95 ;;
96 sub al,(1<<ADDRESSING_MODE_FIELD_POSITION)
97 jz ConvertLCHStoPCHS ; 1, ADDR_DPT_PCHS
98
99;; Fall-through ; 2, ADDR_DPT_LBA28 and 3, ADDR_DPT_LBA48
100
101;---------------------------------------------------------------------
102; Converts LCHS parameters to 28-bit LBA address.
103; Only 24-bits are used since LHCS to LBA28 conversion has 8.4GB limit.
104; LBA = ((cylToSeek*headsPerCyl+headToSeek)*sectPerTrack)+sectToSeek-1
105;
106; Returned address is in same registers that
107; Address_DoNotConvertLCHS and Address_ConvertLCHStoPCHS returns.
108;
109; ConvertLCHStoLBARegisterValues:
110; Parameters:
111; BL: Sector number (1...63)
112; BH: Head number (0...255)
113; CX: Cylinder number (0...1023)
114; DS:DI: Ptr to Disk Parameter Table
115; Returns:
116; BL: LBA Low Register / Sector Number Register (LBA 7...0)
117; CL: LBA Mid Register / Low Cylinder Register (LBA 15...8)
118; CH: LBA High Register / High Cylinder Register (LBA 23...16)
119; BH: Drive and Head Register (LBA 27...24)
120; Corrupts registers:
121; AX, DX
122;--------------------------------------------------------------------
123ALIGN JUMP_ALIGN
124ConvertLCHStoLBARegisterValues:
125 ; cylToSeek*headsPerCyl (18-bit result)
126 mov ax, cx ; Copy Cylinder number to AX
127 eMOVZX dx, BYTE [di+DPT.bHeads]
128 mul dx ; DX:AX = cylToSeek*headsPerCyl
129
130 ; +=headToSeek (18-bit result)
131 add al, bh ; Add Head number to DX:AX
132 adc ah, dh ; DH = Zero after previous multiplication
133 adc dl, dh
134
135 ; *=sectPerTrack (18-bit by 6-bit multiplication with 24-bit result)
136 mov cx, LBA_ASSIST_SPT ; Load Sectors per Track
137 xchg ax, dx ; Hiword to AX, loword to DX
138 mul cl ; AX = hiword * Sectors per Track
139 mov bh, al ; Backup hiword * Sectors per Track
140 xchg ax, dx ; Loword back to AX
141 mul cx ; DX:AX = loword * Sectors per Track
142 add dl, bh ; DX:AX = (cylToSeek*headsPerCyl+headToSeek)*sectPerTrack
143
144 ; +=sectToSeek-1 (24-bit result)
145 xor bh, bh ; Sector number now in BX
146 dec bx ; sectToSeek-=1
147 add ax, bx ; Add to loword
148 adc dl, bh ; Add possible carry to byte2, BH=zero
149
150 ; Copy DX:AX to proper return registers
151 xchg bx, ax ; BL = Sector Number Register (LBA 7...0)
152 mov cl, bh ; Low Cylinder Register (LBA 15...8)
153 mov ch, dl ; High Cylinder Register (LBA 23...16)
154 mov bh, dh ; Drive and Head Register (LBA 27...24)
155 ret
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