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A real question about EEPROM vs. Flash

R

Rich Grise

Jan 1, 1970
0
So, I'm bidding this ultra-sweet project, and I'm studying the
data sheet of the PIC18F6520/8520/6620/8620/6720/8720, and it
says, Flash: 100,000 cycles, EEPROM: 1,000,000 cycles. What
are the other differences? Is flash cheaper than EEPROM? I
have noticed that it tends to get used for program memory,
and EEPROM for data, but are there any other differences,
like, maybe program/cycle time, erase modes, that sort of
thing?

Thanks,
Rich
 
B

Bozzion

Jan 1, 1970
0
Rich Grise said:
So, I'm bidding this ultra-sweet project, and I'm studying the
data sheet of the PIC18F6520/8520/6620/8620/6720/8720, and it
says, Flash: 100,000 cycles, EEPROM: 1,000,000 cycles. What
are the other differences? Is flash cheaper than EEPROM? I
have noticed that it tends to get used for program memory,
and EEPROM for data, but are there any other differences,
like, maybe program/cycle time, erase modes, that sort of
thing?

Thanks,
Rich

yes, it is on the data sheets
 
A

Andy Peters

Jan 1, 1970
0
Rich said:
So, I'm bidding this ultra-sweet project, and I'm studying the
data sheet of the PIC18F6520/8520/6620/8620/6720/8720, and it
says, Flash: 100,000 cycles, EEPROM: 1,000,000 cycles. What
are the other differences? Is flash cheaper than EEPROM? I
have noticed that it tends to get used for program memory,
and EEPROM for data, but are there any other differences,
like, maybe program/cycle time, erase modes, that sort of
thing?

Betcha you can only do page or block erase for the Flash, but you
should be able to erase and write to single bytes in the EEPROM.

If I wasn't lazy, I'd look that up on the data sheet to be sure.

-a
 
S

Svilen

Jan 1, 1970
0
A lot of differencies, starting from the physical effect. Flash is based
on the effect of hot electrons (if I remember correctly) and by nature
it is a descructive effect, that is not the case with the EEPROM. Flash
basic cell is much smaller that the EEPROM one, however the periphery is
much much bigger, that's why the chips are cost effective for big amount
of memory. With EEPROM should be the opposite.
The other big difference is the erase/write time - much shorter(faster)
for the flash, but always on blocks - i.e. a single cell can't be
erased/programed. This is not a limitation for the EEPROM, but the
write/erase time is is much slower.

Hope this helps
Svilen
 
R

Rich Grise

Jan 1, 1970
0
A lot of differencies, starting from the physical effect. Flash is based
on the effect of hot electrons (if I remember correctly) and by nature
it is a descructive effect, that is not the case with the EEPROM. Flash
basic cell is much smaller that the EEPROM one, however the periphery is
much much bigger, that's why the chips are cost effective for big amount
of memory. With EEPROM should be the opposite. The other big difference is
the erase/write time - much shorter(faster) for the flash, but always on
blocks - i.e. a single cell can't be erased/programed. This is not a
limitation for the EEPROM, but the write/erase time is is much slower.

Hope this helps

Yes, considerably!

:)
Thanks!
Rich
 
B

Bob Monsen

Jan 1, 1970
0
Rich said:
So, I'm bidding this ultra-sweet project, and I'm studying the
data sheet of the PIC18F6520/8520/6620/8620/6720/8720, and it
says, Flash: 100,000 cycles, EEPROM: 1,000,000 cycles. What
are the other differences? Is flash cheaper than EEPROM? I
have noticed that it tends to get used for program memory,
and EEPROM for data, but are there any other differences,
like, maybe program/cycle time, erase modes, that sort of
thing?

Thanks,
Rich

Many of the low end PICs can't write their own flash. Thus, EEPROM is
the only non-volatile storage for them.

Flash usually starts out as 1s, and can be set to 0s. Erased flash thus
contains FF. Erasing can usually only be done on a page basis, and takes
a long time.

--
Regards,
Bob Monsen

If a little knowledge is dangerous, where is the man who has
so much as to be out of danger?
Thomas Henry Huxley, 1877
 
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