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Re: Using 28F256 in a 747 instead of 2732A??????????



Kevin Reynolds wrote:
> 
> Shawn wrote,
> If you remove the chip from the MEMCAL carrier, it might be easier to
> swap in a 28F256 in its place to allow you to erase and write to it
> without requiring UV.
> 
> How does this work?
> Do I then just plug this chip into the ECM without a "Holder"?
> This would be great since I was just about to buy an eraser and now could
> put that money into chips.
> Is there any draw backs/downside to doing this?
> How is the 28F256 different? Size, storage amount, speed?

Squash pretty much answered your questions, but I'll add that you
probably need to solder the new chip into the MEMCAL carrier.  The
original PROM is currently soldered in the MEMCAL carrier, but it is
easily removed without much desoldering, in fact, a small flathead
screwdriver can break the soldered connection in my experience and let
you take out the old chip.  Then you can solder a 28F256 in its place.
No drawbacks that I know of to doing it.
The 28F256 is a Flash version of the 27C256.  It has the same number of
pins and same pinout except it is usually made of plastic and has no
window (EPROMs are usually made of gray ceramic and have a window). 
Same storage amount, I think speed is similar or very close.  Then all
you need to do is make an adapter so you can connect the entire MEMCAL
to your programmer and erase/write to it as much as you want.
No downsides to doing this that I'm aware of, but I personally haven't
done it (yet).

My programmer is PC based and has Erase as a menu option.  That blanks
out the whole chip and makes it ready for programming.  It's pretty easy
to do.  I used to make a few dollars several years ago programming Flash
ROM chips for people that accidentally screwed them up when trying to
upgrade the BIOS on their PCs.

Shawn
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