source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int19h.asm@ 273

Last change on this file since 273 was 258, checked in by gregli@…, 13 years ago

Added floppy drive emulation over the serial connection (MODULE_SERIAL_FLOPPY). Along the way, various optimizations were made to stay within the 8K ROM size target. Also, serial code now returns the number of sectors transferred.
File size: 5.2 KB
Line 
1; Project name : XTIDE Universal BIOS
2; Description : Int 19h Handler (Boot Loader).
3
4; Section containing code
5SECTION .text
6
7;--------------------------------------------------------------------
8; INT 19h handler that properly reboots the computer when
9; INT 19h is called.
10;
11; Int19h_ResetHandler
12; Parameters:
13; Nothing
14; Returns:
15; Never returns (reboots computer)
16;--------------------------------------------------------------------
17Int19h_ResetHandler:
18 mov ax, BOOT_FLAG_WARM ; Skip memory tests
19 jmp Reboot_ComputerWithBootFlagInAX
20
21
22;--------------------------------------------------------------------
23; Int19h_BootLoaderHandler
24; Parameters:
25; Nothing
26; Returns:
27; Never returns (loads operating system)
28;--------------------------------------------------------------------
29ALIGN JUMP_ALIGN
30Int19h_BootLoaderHandler:
31 ; Install INT 19h handler for proper reboot
32 LOAD_BDA_SEGMENT_TO es, ax
33 mov al, BIOS_BOOT_LOADER_INTERRUPT_19h ; INT 19h interrupt vector offset
34 mov si, Int19h_ResetHandler ; INT 19h handler to reboot the system
35 call Interrupts_InstallHandlerToVectorInALFromCSSI
36 call Initialize_AndDetectDrives ; Installs new boot menu loader
37 ; Fall to .PrepareStackAndSelectDriveFromBootMenu
38
39;--------------------------------------------------------------------
40; .PrepareStackAndSelectDriveFromBootMenu
41; Parameters:
42; ES: BDA and interrupt vector segment (zero)
43; Returns:
44; Never returns (loads operating system)
45;--------------------------------------------------------------------
46.PrepareStackAndSelectDriveFromBootMenu:
47 STORE_POST_STACK_POINTER
48 SWITCH_TO_BOOT_MENU_STACK
49 ; Fall to .InitializeDisplay
50
51;--------------------------------------------------------------------
52; .InitializeDisplay
53; Parameters:
54; Nothing
55; Returns:
56; Never returns (loads operating system)
57;--------------------------------------------------------------------
58.InitializeDisplay:
59 ; Change display mode if necessary
60 mov ax, [cs:ROMVARS.wDisplayMode] ; AH 00h = Set Video Mode
61 cmp al, DEFAULT_TEXT_MODE
62 je SHORT .InitializeDisplayLibrary
63 int BIOS_VIDEO_INTERRUPT_10h
64.InitializeDisplayLibrary:
65 call BootMenuPrint_InitializeDisplayContext
66 ; Fall to .SelectDriveToBootFrom
67
68;--------------------------------------------------------------------
69; .SelectDriveToBootFrom
70; Parameters:
71; Nothing
72; Returns:
73; Never returns (loads operating system)
74;--------------------------------------------------------------------
75.SelectDriveToBootFrom:
76 call RamVars_GetSegmentToDS
77 cmp WORD [cs:ROMVARS.wfDisplayBootMenu], BYTE 0
78 jne SHORT ProcessBootMenuSelectionsUntilBootableDriveSelected ; Display boot menu
79 ; Fall to BootFromDriveAthenTryDriveC
80
81;--------------------------------------------------------------------
82; BootFromDriveAthenTryDriveC
83; Parameters:
84; DS: RAMVARS segment
85; Returns:
86; Never returns (loads operating system)
87;--------------------------------------------------------------------
88BootFromDriveAthenTryDriveC:
89 xor dx, dx ; DL = 00h = Floppy Drive A
90 call BootSector_TryToLoadFromDriveDL
91 jc SHORT Int19hMenu_JumpToBootSector_or_RomBoot
92 mov dl, 80h ; DL = 80h = First Hard Drive (usually C)
93 call BootSector_TryToLoadFromDriveDL
94 jmp SHORT Int19hMenu_JumpToBootSector_or_RomBoot ; ROM Boot if error
95
96
97;--------------------------------------------------------------------
98; ProcessBootMenuSelectionsUntilBootableDriveSelected
99; Parameters:
100; DS: RAMVARS segment
101; Returns:
102; Never returns
103;--------------------------------------------------------------------
104ProcessBootMenuSelectionsUntilBootableDriveSelected:
105 call BootMenu_DisplayAndReturnSelectionInDX
106 call DriveXlate_ToOrBack ; Translate drive number
107 call BootSector_TryToLoadFromDriveDL
108 jnc SHORT ProcessBootMenuSelectionsUntilBootableDriveSelected ; Boot failure, show menu again
109 ; Fall to Int19hMenu_JumpToBootSector_or_RomBoot
110 ; (CF is set or we wouldn't be here, see "jnc" immediately above)
111
112;--------------------------------------------------------------------
113; Int19hMenu_JumpToBootSector_or_RomBoot
114;
115; Switches back to the POST stack, clears the DS and ES registers,
116; and either jumps to the MBR (Master Boot Record) that was just read,
117; or calls the ROM's boot routine on interrupt 18.
118;
119; Parameters:
120; DL: Drive to boot from (translated, 00h or 80h)
121; CF: Set for Boot Sector Boot
122; Clear for Rom Boot
123; ES:BX: (if CF set) Ptr to boot sector
124;
125; Returns:
126; Never returns
127;--------------------------------------------------------------------
128ALIGN JUMP_ALIGN
129Int19hMenu_JumpToBootSector_or_RomBoot:
130 mov cx, es ; Preserve MBR segment (can't push because of stack change)
131 mov ax, 0 ; NOTE: can't use XOR (LOAD_BDA_SEGMENT_TO) as it impacts CF
132 SWITCH_BACK_TO_POST_STACK
133
134; clear segment registers before boot sector or rom call
135 mov ds, ax
136 mov es, ax
137%ifdef USE_386
138 mov fs, ax
139 mov gs, ax
140%endif
141 jnc SHORT .romboot
142
143; jump to boot sector
144 push cx ; sgment address for MBR
145 push bx ; offset address for MBR
146 retf ; NOTE: DL is set to the drive number
147
148; Boot by calling INT 18h (ROM Basic of ROM DOS)
149.romboot:
150 int BIOS_BOOT_FAILURE_INTERRUPT_18h ; Never returns
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