Re: firmware for the PseudoDisk

[bieling@terra.es]

Michael J. Mahon ha escrito:

> Alex Freed wrote:
>
> > What I want is some code loaded into Apple at boot time that will
> > parse the SD card's directory and allow the user to select a
> > file - ProDOS volume or a NIB image. Reading raw sectors from
> > the SD card is trivial via the ProDOS interface. Somebody needs to
> > write an Apple application to do it.
> >
> > I'm sure there are many people on this list more qualified than me.
> > So I'll probably write a very simple one and let somebody else
> > improve on it.
>
> So you are suggesting a read-only FAT16 file system implemented
> as a boot-code selector to "boot" the chosen file (Apple volume)
> for actual use?
>
> The booted OS would then use read/write drivers for to then carry
> out the two-level mapping as the OS runs from the pseudo-volume--
> in ROM, I expect.  The mapping to physical sectors is done
> transparently by code running on the card that understands FAT16, yes?
>
> -michael

That's a good question.
Who is going to translate prodos blocks to sd blocks ?
The 6502+prodos driver or the AVR+code inside it ?

Alex, when you say "The hardware works great. The firmware is very
simple but seems to do the job. There is a huge room to improve on it:
the code takes a small fraction of memory even though it is written in
"C"." you're talking about the avr code, I think, yes ?

If so, do you think that there's enough space left (in the AVR) to add
code to parse a *fat16* filesystem and (pre) build (at boot time) and
keep in AVR's ram a prodos-block to sd-physical-block *table* given an
image file as the parameter, so that the translation is done
"transparently" for the 6502/apple2 prodos driver ?

What about doing it for more than one (online) disk images ?

Regards,
Jorge Chamorro B.