cos2000v1/boot.asm

220 lines
4.5 KiB
NASM
Executable File
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boots segment
.386
org 7C00h
;org 100h
assume cs:boots,ds:boots
start:
jmp boot
bootdb db 'COS2000A' ;Fabricant + n°série Formatage
sizec dw 512 ;octet/secteur
db 1 ;secteur/cluster
reserv dw 1 ;secteur reserv
nbfat db 1 ;nb de copie de la FAT
nbfit dw 25 ;taille rep racine
allclu dw 2880 ;nb secteur du volume si < 32 még
db 0F0h ;Descripteur de média
fatsize dw 12 ;secteur/FAT
nbtrack dw 18 ;secteur/piste
head dw 2 ;nb de tˆteb de lecture/écriture
hidden dd 0 ;nombre de secteur cachs
dd 0 ;si nbsecteur = 0 nbsect ; the number of sectors
bootdrv db 0 ;Lecteur de dmarrage
db 0 ;NA
bootsig db 29h ;boot signature 29h
dd 01020304h ;no de serie
pope db 'COS2000 ' ;nom de volume
db 'FAT16 ' ;FAT
specialboot:
errorloading db 'It''s not a COS disk!',0dh,0ah,0
okloading db 'COS search system',0Dh,0ah,0
syst db 'Ok',0dh,0ah,0
dot db '.',0
carry db 0dh,0ah,0
Sys db 'system',0,0,0,0,0,0
sys2 db 'sys',0
errorboot:
mov si,offset errorloading
call showstr
mov ah,0
int 16h
int 19h
boot:
mov Bootdrv,dl
cli
mov ax,09000h
mov ss,ax
mov sp,0FFFFh
sti
p:
push cs
pop ds
xor ax,ax
int 13h
jc errorboot
mov si,offset okloading
call showstr
mov cx,nbtrack
les si,ds:[1Eh*4]
mov byte ptr es:[si+4], cl
mov byte ptr es:[si+9], 0Fh
xor ax,ax
mov al,NbFat
mov bx,FatSize
mul bx
mov cx,ax
add cx,word ptr [offset Hidden]
adc cx,word ptr [offset Hidden+2]
add cx,Reserv
mov word ptr [offset BootSig],cx
xor dx,dx
mov ax,allclu
div nbtrack
xor dx,dx
div head
mov word ptr [offset pope],ax
push cs
pop es
mov bx,offset buffer
mov si,bx
xor dx,dx
CheckRoot:
call readsector
jc errorboot
xor di,di
findnext:
cmp byte ptr [bx+di],0
je errorboot
push si di cx
mov si,di
add si,bx
call showstr
mov ax,si
mov si,offset dot
call showstr
mov si,ax
add si,12
call showstr
mov si,offset carry
call showstr
mov si,ax
mov di,offset sys
mov cx,12+4
rep cmpsb
pop cx di si
je oksystem
add di,32
inc dx
cmp dx,nbfit
ja errorboot
cmp di,sizec
jb findnext
inc cx
jmp Checkroot
oksystem:
mov si,offset syst
call showstr
mov cx,[di+BX+26]
mov bx,200h
mov es,bx
push bx
mov bx,0100h
push bx
mov si,offset dot
fatagain:
cmp cx,0FFF0h
jae finishload
call readsector
jc errorboot
call showstr
add bx,sizec
call getfat
jnc fatagain
finishload:
push es
push es
push es
pop ds
pop fs
pop gs
push 7202h
popf
db 0CBh
;<-cx nøsecteur ->cx code FAT
getfat:
push es bx
mov ax,cx
xor dx,dx
div sizec
mov cx,ax
add cx,reserv
mov bx,offset buffer
push cs
pop es
call readsector
jc errorgetfat
shl dx,1
add bx,dx
mov cx,[bx]
errorgetfat:
pop bx es
ret
ReadSector:
push ax cx dx si
mov AX, CX
xor DX, DX
div nbtrack
mov CL, DL ;{ Set the sector }
and CL, 63 ;{ Top two bits are bits 8&9 of the cylinder }
xor DX, DX
div word ptr pope
mov CH, DL ;{ Set the track bits 0-7 }
mov AL, DH
ror AL, 1
ror AL, 1
and AL, 11000000b
or CL, AL ;{ Set bits 8&9 of track }
xor dX, DX
div head
mov DH, DL ;{ Set the head }
inc CL
mov SI, 4
TryAgain:
mov AX,0201h
mov DL, bootdrv
int 13h
jnc Done
dec SI
jnz TryAgain
Done:
pop si dx cx ax
ret
showstr:
push ax bx si
again:
lodsb
or al,al
jz fin
mov ah,0Eh
mov bx,07h
int 10h
jmp again
fin:
pop si bx ax
ret
Buffer equ $
boots ends
end start