Introduction.While I couldn't find any vendor that had still the NM29A080 serial flash EEPROM chip used in the Expander SF by Mel Tsai, I looked for a way to use another chip. Note however that what is presented here It hasn't been made nor tested yet; I'm waiting to recieve the chip.
I found a full range of flash
EEPROMS at Samsung. I'm thinking to use the 32MBit and 64MBit versions(while
all others can also work with the same hardware). A PIC16C57 will be used
as an interface between the calc an the memory. I haven't yet written a
single code of the PIC program, but if it was relativily small (I doubt..)
it could fit in a PIC16C55.
Shematics.Here is the basic schematic: I think that the hardware will not be changed until the final version, but if someone want to build it now and wait for the final release, I can't promise him... (Note: I forgot to draw the Crystal resonator of the PIC16C57)
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Author : Sami Khawam