At 05:53 PM 3/17/99 +0100, you wrote:
>>If so, a FAT16 driver should not in any way depend on a certain type
>>of hardware/ROM, only change things that are the same with any disk
>>interface. Or any DOS2-using interface, if you like.
>
>Yes, the standard way for accessing physical sectors is through routine
>#4010 of diskROM. But the standard input parameters specification for this
>routine allows only the use of 16 bit sector numbers. So, for accessing 24
>bits sector numbers a controller specific routine is needed.
So you are actually doing 2 upgrades at once?
Upgrades being:
1. 16bit sector numbers -> 24bit sector numbers
(allows partitions >32MB)
2. FAT12 -> FAT16
(keeps cluster size reasonable when partitions go beyond 32MB)
>Besides I need
>to set the "disk change" flag under certain circumstances, and (AFAIK)
>there is not standard diskROM routine for this.
SET the disk change flag? Why do you need to do that?
Reading the flag is perfectly possible using diskROM, but you probably
already knew that.
>I also don't know how sector buffers works,
Sector buffers are a kind of cache. They are located in the 32K of memory
that DOS2 claims.
If a sector is requested and it is located in a sector buffer, the content
of the buffer is returned instead of reading the sector from disk. This is
the mechanism that allows a turbo R to display "files" in BASIC a second
time without accessing the drive.
Disk buffers are invalidated whenever disk change status is "changed" or
"unsure". If your MSX has hardware disk change checking (like turbo R), the
hardware signal is used. Otherwise, the status will be "not changed" for a
certain number of interrupts.
Bye,
Maarten
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