Re: EEPROM Parts (Was: Re: Flashboard questions...)

I'll see what I can find. I used to have a pair of BASIC Stamp boards
that had an on-board programmable 16kb EEPROM that ran entirely upon a
9v battery -- quite impressive at the time (early experiments with
electronics and PICs -- my, what fun that was =o).

On 11/9/06, Mark Gollahon <[email protected]> wrote:
> June:
>
> If I remember correctly (its been awhile since I looked at an EEPROM
> data sheet), EEPROM needs some pretty hefty voltages for the erase
> and write cycles -- voltages that don't exist in the Jornada
> currently.  If that is the case, flash is easier to use because it
> doesn't need those voltages.  If you can find some EEPROM that is a
> 128Mbit or 256Mbit part organized in a x16 array that is cheaper
> than flash and doesn't need programming voltages, I'd be quite
> willing to look at using the part.  I would really like it to be a
> BGA instead of TSOP (BGA has a much smaller physical footprint).
>
> I've looked at the BGA flash and RAM parts and they take up less
> than half the space as the original TSOP parts!  Leaves me some
> room for one of those "surprises" I want to add....
>
> Regards,
> -MarkG
>
>
> June Tate-Gans wrote ..
> > That being said, has anyone stopped to consider using EEPROMs instead
> > of Flash? Last I checked those were a bit easier to program on-board.
> > =o)
> >
> > On 11/8/06, June Tate-Gans <[email protected]> wrote:
> > > The WRT54G is addressing the card in a serial manner through some
> > > other native interface on the boards (in their case, they're using the
> > > GPIO pins on the CPU -- something we don't have direct access to
> > > through the ROM board).
> > >
> > > The trick here is that the ROMs act as main system memory -- they are
> > > directly addressable by the CPU as a memory space (which,
> > > incidentally, is why Linux can't boot after a shutdown or reboot --
> > > memory address 0x00000000 is literally the beginning of the ROM), and
> > > we do not have the niceties of GPIO pins to prepare and use the SD
> > > card before the CPU turns on/while it's running.
> > >
> > > To integrate SD/MMC cards into the Jornada's architecture would
> > > require all kinds of weird workarounds because SD/MMC memory is
> > > accessed serially instead of directly like traditional RAM. The SD/MMC
> > > design requires you to send several things all in serial:
> > >
> > >   1. Send the SD/MMC card address
> > >   2. Send the address offset in the SD/MMC
> > >   3. Send/recieve your data
> > >
> > > Note that before you can even approach this, you have to have
> > > /assigned/ the address to the SD/MMC card before you can really talk
> > > to it. Keep in mind that this is the only /feasable/ way you can talk
> > > to an SD/MMC card -- there is no other cost effective method (native
> > > SD mode costs mucho $$$ and still isn't a solution that is viable
> > > since it's also not directly addressable). CF cards, on the other
> > > hand, have similar issues as they are literally designed to emulate
> > > the ATA interface provided by PCMCIA in a smaller package -- which is
> > > why you can stick a CF into a PCMCIA card reader and read it just like
> > > a typical ATA disk.
> > >
> > > Traditional addressable memory is addressed in a much simpler fashion:
> > >
> > >   - Write the address to the address portion of the memory bus
> > >   - Read/write your data
> > >
> > > Note that both of these operations typically happen in the same CPU
> > > cycle, whereas the SD/MMC method would require several cycles to
> > > complete. Because of this fundamental difference, you would likely end
> > > up with timing issues as well. Keep in mind, I'm not saying it's
> > > impossible, but it would be considerably more complex than using a set
> > > of flash chips built onto a new board, and would be much less stable.
> > >
> > > On 11/8/06, Chris Davis <[email protected]> wrote:
> > > > Ok, but you are missing my point, then..  There are different modes
> > of connecting memory cards to devices than ide.  Just look at the Linksys
> > wrt54g SD card mod.  That router DOES NOT have anything resembling a IDE/ATA
> > interface.
> > > >
> > > > While Compact flash is based on a IDE type interface, SD cards are
> > not.
> > > >
> > > > -------------
> > > > Subject: RE: [jornada] Flashboard questions...
> > > >    From: "Tim Underwood" <[email protected]>
> > > >    Date: Wed, 8 Nov 2006 12:24:48 -0600
> > > >      To: <[email protected]>
> > > >
> > > > To use a SD/CF/etc card requires an ATA interface.
> > > >
> > > > Simply not available on the ROM board or flash board.  That's a whole
> > > > different animal.  The ROM/mem board is just that - memory.  The OS
> > does
> > > > some magic to make the ROM magically appear in RAM (kinda similar to
> > a
> > > > RAM disk - but it isn't).
> > > >
> > > > To read/write mem cards is completely different, and a completely
> > > > different circuit and interface methodology.  You can't just unsolder
> > > > the ROM, and solder on a connector to put in an SD/CF/whatever card.
> > > >
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > jornada mailing list
> > > > [email protected]
> > > > https://handhelds.org/mailman/listinfo/jornada
> > > >
> > >
> > >
> > > --
> > > June Tate-Gans    | Don't try to outweird me, three-eyes. I get stranger
> > things
> > > www.theonelab.com | than you free with my breakfast cereal. -- Zaphod
> > Beeblebrox
> > >
> >
> >
> > --
> > June Tate-Gans    | Don't try to outweird me, three-eyes. I get stranger
> > things
> > www.theonelab.com | than you free with my breakfast cereal. -- Zaphod Beeblebrox
> > _______________________________________________
> > jornada mailing list
> > [email protected]
> > https://handhelds.org/mailman/listinfo/jornada
>
>


-- 
June Tate-Gans    | Don't try to outweird me, three-eyes. I get stranger things
www.theonelab.com | than you free with my breakfast cereal. -- Zaphod Beeblebrox