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 ;----------------------------------------------------;
 ; Load entire a program.                             ;
 ;----------------------------------------------------;
LoadImage:
        mov   ax,[cluster]   ; In here is the cluster we saved
        mov   [FloppyTest],0 ; this is the nunmber of retrys
ReadNextClusterUP:
        call  ClusterLBA     ; convert
        call  ReadSectors    ; your read floppy function
        jc    ErrorFloppy    ; error
 ;----------------------------------------------------;
 ; compute next cluster.                              ;
 ;----------------------------------------------------;
        mov   ax,word[cluster] ; here is the cluster number (2)
        mov   cx,ax
        mov   dx,ax
        shr   dx,0x0001 ; div it by 2 = (1)
        add   cx,dx ; = (3)
        mov   esi,BpbFat12 move the address of the the FAT into esi
        add   esi,ecx ; add (3) to the address
        mov   dx,word [ds:esi] ;load whats at that address, in to DX
        test  ax,0x0001 ; test if its odd or even ?
        jnz   OddCluster
EvenCluster:
        and   dx,0000111111111111b ; if even 0 out right most nibble
        jmp   Done
OddCluster:
        shr   dx,0x0004  ; if odd shift 4 right
Done:
        mov   word [cluster],dx ; Now test if its FF0H eg end of file
        cmp   dx,0x0FF0
        jb    LoadImage ; if not load some more as its not end of file.
 ;----------------------------------------------------;
 ; ExitSucsess.                                       ;
 ;----------------------------------------------------;
ExitSucsess:
        call  Fdd_motor_off
        mov   [ErrorCode],0
        pop   ds
        pop   es
        popad
        mov   ebx,dword[FddSectorsLoadedCount] ; Put number of sectors load, in ebx.
        mov   ah,0
        clc
        ret
 ;----------------------------------------------------;
 ; ErrorFloppy.                                       ;
 ;----------------------------------------------------;
ErrorFloppy:
        call  Fdd_motor_off
        pop   ds
        pop   es
        popad
        mov   ah,byte[ErrorCode]
        stc
        ret

 ;----------------------------------------------------;
 ; ReadSectors.                                       ;
 ;----------------------------------------------------;

ReadSectors:
        pushad
        push  es
        push  ds
        call  LBAcHs
TryReadFloppyAgain:
        mov   ch,byte [absoluteTrack]
        mov   cl,byte [absoluteSector]
        mov   dh,byte [absoluteHead]
        mov   dl,byte [bsDriveNumber]
        call  FddRead ; you call your floppy function here
        jnc   FloppyReadOK

 ;----------------------------------------------------;
 ; Try Reading floppy 3 time.                         ;
 ;----------------------------------------------------;
        inc   [FloppyTest]
        cmp   [FloppyTest],4
        jae    @f
        call  FddRecalibrate
        jmp   TryReadFloppyAgain
 ;----------------------------------------------------;
 ; Move data from DMA buffer, to image address.       ;
 ;----------------------------------------------------;
FloppyReadOK:
        mov   cx,512
        mov   ax,sys_data
        mov   ds,ax
        mov   es,ax
        mov   esi,OffsetDma2Buffer ; this points to the DMAbuffer
        mov   edi,[LoadFileToAddress] ; this points to the file load address
        add   edi,[FileLoadCount]; each time we loop, we need to add 512 more bytes
        rep   movsb
        add   [FileLoadCount],512
        add   [FddSectorsLoadedCount],1  ; add 1 to number of sectors load count.
 ;----------------------------------------------------;
 ; ExitSucsess.                                       ;
 ;----------------------------------------------------;
        pop   ds
        pop   es
        popad
        clc
        ret
 ;----------------------------------------------------;
 ; Error.                                             ;
 ;----------------------------------------------------;
@@:
        pop   ds
        pop   es
        popad
        stc
        ret

 ;----------------------------------------------------;
 ; LBAcHs.                                            ;
 ;----------------------------------------------------;

LBAcHs:
        div   word [bpbSectorsPerTrack]
        inc   dl
        mov   byte [absoluteSector],dl
        xor   dx,dx
        div   word [bpbHeadsPerCylinder]
        mov   byte [absoluteHead],dl
        mov   byte [absoluteTrack],al
        ret

 ;----------------------------------------------------;
 ; ClusterLBA.                                        ;
 ;----------------------------------------------------;

ClusterLBA:
	sub   ax,2 ;we sub the first 2 entrys
	xor   cx,cx
	mov   cl,byte[bpbSectorsPerCluster] ; in this case 1
	mul   cx
	add   ax, word [DataStart] ; here is the start of the data on the floppy
	ret
; NOTE: You can get the DATA start address by Reserved_Sectors + FAT_Sectors + Root_Sectors

Code: Select all

KERNEL.BIN cluster = 00CE = 206 (EC = 236)
Correct? No, starts at 233
236 - 233 = 3...

RootDirSectors = ((BPB_RootEntCnt * 32) + (BPB_BytsPerSec – 1)) / BPB_BytsPerSec;
= ( ( 224 * 32 ) + ( 512 - 1 ) ) / 512;
= ( 7168 + 511 ) / 512
= 7679 / 512 = 14.998046875 = 15 ??? decimals???

FirstDataSector = BPB_ResvdSecCnt + (BPB_NumFATs * FATSz) + RootDirSectors;
= 1 + ( 2 * 9 ) + 14.998046875 = 33

FirstSectorofCluster = ((N – 2) * BPB_SecPerClus) + FirstDataSector;
= ( ( 236 - 2 ) * 1 ) + 33 = 267

Code: Select all

KERNEL.BIN cluster = 00CE = 206 (EC = 236)

RootDirSectors = ((BPB_RootEntCnt * 32) + (BPB_BytsPerSec – 1)) / BPB_BytsPerSec;
= ( ( 224 * 32 ) + ( 512 - 1 ) ) / 512;
= ( 7168 + 511 ) / 512
= 7679 / 512 = 14.998046875 => 14 (cutoff)

FirstDataSector = BPB_ResvdSecCnt + (BPB_NumFATs * FATSz) + RootDirSectors;
= 1 + ( 2 * 9 ) + 14 = 33

FirstSectorofCluster = ((N – 2) * BPB_SecPerClus) + FirstDataSector;
= ( ( 206 - 2 ) * 1 ) + 33 = 235

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short Sector = ( buff[j+26] << 8 ) | buff[j+27];

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short Sector = ( ( buff[j+27] << 8 ) | buff[j+26] ) + 31;