Re: EEPROM Circuit?

["Glenn Jones" <rg.jones@rogers.com>]

"Michael J. Mahon" <mjmahon@aol.com> wrote in message
20040409204614.01174.00000110@mb-m14.aol.com">news:20040409204614.01174.00000110@mb-m14.aol.com...
> Glenn Jones replied:
>
> >> In general, byte-wide EEPROMs are much simpler to
> >> interface to a byte-wide bus--in fact the Apple bus has
> >> most of the decoding done for you.
> >>
> >> -michael
> >>
> >> Check out amazing quality sound for 8-bit Apples on my
> >> Home page:  http://members.aol.com/MJMahon/
> >
> >Thanks for the info  .. I was trying to keep the physical size
> >of the chip to a minimum and serial eeproms tend to be very
> >small compared to byte wde eeproms that require 8 data lines
> >plus address etc
> >
> >given what you just said .. the combined size of the additional glue
> >to access as serial eeprom might end up being equivilent or larger
> >than a byte wide eeprom
>
> That is true, unless you happen to have some unused I/O
> pins around, plus some firmware/software space to control them.
>
> Many microcontrollers include some EEPROM for program
> and parameter storage--maybe the one on the ethernet module
> is one of them.
>
> -michael
>
> Check out amazing quality sound for 8-bit Apples on my
> Home page:  http://members.aol.com/MJMahon/

No nonvolatile storage or extra ports on this module.

The module does have an i2c interface but that is for the module interface
if you choose that vs direct or indirect modes

Apparently one can also use some spare ram on the module $300- $3FFF but it
is volatile.  :O(

Their reference example shows using the 24c02
with a 8051 which has ports that can be used to bit bang ic2.
Most new microcontrollers are coming with i2c embedded masters as well

I just found this chip ..have to do more reading .. it might help

http://www.semiconductors.philips.com/acrobat/datasheets/PCF8584_4.pdf


An other option might be to emulate the annunciator and push button
circuitry in the apple.

I guess i should decide on one vs two wire interface first ....

Glenn

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