read sectors from disk failed with timeout

09-02-2011

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read sectors from disk failed with timeout

i'm writing some code to simulate the boot progress after power on
but when i try to read the 2nd sector from a floppy disk, this operation always fail with ah=0x80h which means timeout, how can i get over this problem?
my code would be like this:

Code:

[jack@localhost 1]$ cat boot.S
.code16
#define SETUPLEN  4
#define BOOTSEG  0x7C0
#define INITSEG  0x900

.text
a:
mov $BOOTSEG, %ax
mov %ax, %ds
mov $INITSEG, %ax
mov %ax, %es
mov $256, %cx
sub %si, %si
sub %di, %di
rep
movsw

jmp 0x9000+go-a

go:
mov %cs, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %ss
mov $0xFF00, %sp

load_setup:
mov $0x0000, %dx
mov $0x0002, %cx
mov $0x0200, %bx
mov $0x0200+SETUPLEN, %ax
int $0x13                           //timeout happens here
jnc ok_load_setup
mov $0x0000,%dx
mov $0x0000,%ax
int $0x13
jmp load_setup

ok_load_setup:
mov $0x00, %dl
mov $0x0800, %ax
int $0x13
mov $0x00, %ch
mov %cx, %cs 
mov $INITSEG, %ax
mov %ax, %es

mov $0x03, %ah
xor %bh, %bh
int $0x10

mov $24, %cx
mov $0x0007, %bx
mov msg, %bp
mov $0x1301, %ax
int $0x10

msg:
.byte 13, 10


.org 510
.word 0xaa55

looking forward to replies.
really appreciate any suggestion.

wljackhero

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PREP(8) System Manager's Manual PREP(8) NAME
prep, format - prepare hard and floppy diskettes SYNOPSIS
disk/prep [ -ra ] special [ type ] disk/format [ -t type ] [ -f ] [ -d ] [ -b bfile ] [ -c csize ] [ -l label ] drive [ files ... ] DESCRIPTION
A partition table is stored on a hard disk to specify the division of the physical disk into a set of logical units. On Plan 9 the parti- tion table is a list of triples: name, starting sector, and ending sector. The kernel fabricates the first two partitions, disk and parti- tion; the disk partition records the starting and ending sectors for the whole disk, and the partition partition, typically the last sector on the disk, holds the partition table itself. Special is the maximal prefix of names of the logical units on the disk, for example #w/hd0. Prep reads and prints the associated parti- tion table and then enters a simple interactive mode to control editing the table. The options are: -r (read only) prohibits writing the table on disk. -a automatically create default partitions if no partition table already exists. These include partitions for DOS, a boot kernel, an NVRAM substitute, a kfs(4) file system, and, if room remains, a swap partition. Format prepares for use the floppy diskette in the disk file named drive, for example /dev/fd0disk. The options are: -f Do not physically format the disc. Used to install an MS-DOS filesystem on a previously formatted disc. With this option, drive can be a plain file. -t specify a density and type of disk to be prepared. The possible types are: 31/2DD 31/2" double density, 737280 bytes 31/2HD 31/2" high density, 1474560 bytes 51/4DD 51/4" double density, 368640 bytes 51/4HD 51/4" high density, 1146880 bytes The default is the highest possible on the device, unless -f is used, in which case the default is 31/2HD. -d add MS-DOS parameter block, file access table (FAT), and root directory to the start of the floppy. The remaining options have effect only when -d is specified: -b use the contents of bfile as the bootstrap block installed in sector 0. -c use a DOS cluster size of csize sectors when creating the DOS FAT. -l add a label when creating the DOS parameter block. Again under -d, any files listed are added, in order, to the root directory of the MS-DOS filesytem. The files are contiguously allocated and created with the READONLY attribute set. The file /sys/src/boot/pc/bb is an example of a suitable bfile to make the disk a boot disk. It gets loaded by the BIOS at 0x7C00, reads the root directory into address 0x7E00, and looks at the first root directory entry. If that file is called B.COM, it uses single sector reads to load the file into address 0x10000 and then jumps to the loaded file image. EXAMPLE
Create a Plan 9 boot floppy on a previously formatted diskette: disk/format -f -b bb -d /dev/fd0disk /386/b.com SOURCE
/sys/src/cmd/disk/prep.c /sys/src/cmd/disk/format.c /sys/src/boot/pc/bb.s SEE ALSO
floppy(3), wren(3), b.com(8) PREP(8)

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