Re: E(E)PROM pn and speeds

["Shawn R. Lin" <slin01@mail.orion.org>]

Bob Valentine wrote:
> 
> I've just gotten to the point of ordering a burner, now need to get some
> blank roms.    From the archives I got that a 28C256 can be used in place
> of a 27C256, eeprom part instead of eprom, no eraser and quicker writes.
> Questions before I order parts:

No, 28C256 cannot be used in place of 27C256.  If I remember correctly,
A14 and /WE need to be switched around before it can be used.  I was
also told 28C256 program VERY slowly.
28F256 won't work either, it's 32-pins.
The magic chip is the Atmel 29C256.  Its pinout matches, and it is Flash
so fast to program.  5V programming and supports sector
writing/erasing.  They are $3.96/each at JDR Microdevices.  Haven't
tried it personally, but I plan to in the near future.

> 1.  Is the above correct, and same for a 28c512 in place of 27c512?

I don't have pinouts for the 28C512, but the 28F512 and 29C512 both are
32-pin, and NOT pin compatible with the 27C512 which is 28-pin.  The
29C512 has the same pinouts on the lower 28 pins, except VCC is on pin
32 (it's on pin 28 on a 27C512).

> 2.  What speed chips can I use?    Faster than 250ns ok?

I don't know, I've never had any problems using faster chips for what
it's worth.

-- 
Shawn Lin
http://www2.cybercities.com/g/gmwbodycars/
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