More OS problems!!

[thomasantony]

Hi,
    I tried out the scroll functions given in this forum before. I am also making a FAT driver. I am trying to read a 3k file into a 3k buffer. But read fails at sector 53(0 based). Here the problem is that my LBA to CHS routine gives out the sector num as 18 when it should never be greater than 17. I get it like this (LBA % SPT)+1 . As for the scroll function. The system is resetting after it scrolls up. It actually scrolls up about 10 lines before it resets when it should scroll only once. !! :dazzled: Plz tell me what I should do. And abt the sector num I give to the FDC, is it 0based or 1 based. In an example prog I saw, the author uses the above formula itself to get the sector num. ::)

Thomas Antony

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[MichaelW]

CHS sector numbers are 1 based. LBA numbers are 0 based.

Per the ATA/ATAPI 5 standard, for LBA numbers <= 16,514,064:

LBA=(((cyl_number * heads_per_cyl) + head_number) * sectors_per_track) + sector_number – 1

This can be transposed to convert from LBA to CHS, as I did for this QuickBASIC code:

Code Select Expand


SUB GetChs (cyl&, head&, sector&, logicalBlockAddress&, heads&, sectorsPerTrack&)
  ' Translates the LBA specified by <logicalBlockAddress&> to
  ' a CHS address and returns the CHS address in <cyl&>, <head&>,
  ' and <sector&>.
  '
  ' This procedure uses a transposed version of the relationship
  ' specified in the ATA standard for LBA numbers <= 16,514,064.

  cyl& = logicalBlockAddress& \ (heads& * sectorsPerTrack&)
  remainder& = logicalBlockAddress& MOD (heads& * sectorsPerTrack&)
  head& = remainder& \ sectorsPerTrack&
  sector& = remainder& MOD sectorsPerTrack& + 1
END SUB

Note that heads& is the same value as heads_per_cyl.

You can download the draft versions of the ATA/ATAPI and related standards from http://www.t13.org.
Note that the version 6 and later standards refer to the version 5 standard for the LBA/CHS translation.

[thomasantony]

Hi,
    The formula I used was correct. Thaxn for the info anyway. It will be useful when I code the hdd driver. I am now rebuilding my FDC driver THE 2nd TIME :dazzled: :dazzled: . Maybe this time, it will work ok. It was working ok when it read some sectors but there seems to be some problem

Thomas Antony

[BogdanOntanu]

Do not worry i have redesigned the Floppy driver many times and always in small steeps (i guess at least 4 times until now)
And I am still not satisfied ;) i will need a notification callback added to driver requests...

[thomasantony]

Hi,
    Take a look at this. When I call FAT12_LoadFile the code goes into bogus memory on the second call the ReadSector. I think the memory is becoming corrupted or something. I found this using the Bochs debugger.

Thomas Antony :U

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