Serial EEPROM or Serial Flash?

From	pozz <pozzugno@gmail.com>
Newsgroups	comp.arch.embedded
Subject	Serial EEPROM or Serial Flash?
Date	2018-06-14 12:20 +0200
Organization	A noiseless patient Spider
Message-ID	<pftfgp$l3j$1@dont-email.me> (permalink)

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I need to save some data on a non-volatile memory. They are some 
parameters that the user could change infrequently, for example 10 times 
per day at a maximum.  In the range 100-2kB.

As usually occurs, the parameters that changes more frequently (10 times 
per day) are fewer than parameters that changes very rarely (10-100 
times in the device lifetime).

How to save those data? After discarding the internal MCU Flash (because 
of interrupts block during programming), I'm deciding if it's better a 
serial EEPROM or serial Flash.

First of all, I think SPI is better than I2C.  SPI seems much faster: 
10-20MHz against 400kHz-1MHz.  At least for reading.  Erasing/writing 
time is identical between I2C and SPI.

EEPROM or Flash? I know EEPROM can be written one byte at a time without 
erasing an entire block, against Flash that needs a sector erase before 
writing even a single byte.

The firmware would be simpler with EEPROMs, because I don't need to save 
the entire sector before erasing and restoring it during programming, 
when writing a single byte.  With EEPROMs I can write a byte.  Stop.

However I don't think this simple approach can be used in a real 
production.  Suppose I have 10 bytes to write.  What happens if the 
writing process is stopped at the middle, maybe after 5 bytes?  How to 
protect the system against those events?  I think one solution is to 
have at least two copies of data in the memory and switch to the other 
bank after all data is completely written, with an "atomic" write operation.
This means I need to copy&paste an entire block everytime, even for a 
single byte change.  And this is similar to Flash approach, where I 
*need* a sector erase before changing a single byte.

What about the time?  EEPROM write cycle is about 5ms for a 32-bytes 
page. For 128 bytes/4 pages, 20 ms.
Flash sector erase time is 18 ms, plus 14us for each byte. The overall 
write cycle time is similar between EEPROM and Flash.

If the data are bigger, for example 1kB, the Flash technology wins.  The 
sector size in Flash memories are usually bigger than 1kB.  So I need to 
erase only one time (18m + 14u*1024=32ms).  In EEPROM I have 32 32-bytes 
pages, so 5m*32=160ms.  5 times more than Flash.

I'm not considering endurance.  EEPROMs are better (1000k write cycles) 
than Flash (100k write cycles), but I don't need so much write cycles in 
the entire device lifetime.


After those considerations, I think I will choose a serial SPI Flash, 
maybe 512kbit.  The price is similar to serial EEPROM of only 64kbit.
I see only one difficulty: how to write a good device driver to manage 
serial Flash: copy the content of a sector in another sector, making the 
changes on-the-fly, and switch from one sector to the other in one 
"atomic" operation.  Could you suggest some code to study?

I missed something other?  Please share your considerations.

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Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-14 12:20 +0200
  Re: Serial EEPROM or Serial Flash? David Brown <david.brown@hesbynett.no> - 2018-06-14 12:49 +0200
    Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 09:38 +0200
      Re: Serial EEPROM or Serial Flash? Jack <jack4747@gmail.com> - 2018-06-15 00:54 -0700
        Re: Serial EEPROM or Serial Flash? Reinhardt Behm <rbehm@hushmail.com> - 2018-06-15 16:26 +0800
          Re: Serial EEPROM or Serial Flash? Jack <jack4747@gmail.com> - 2018-06-15 01:31 -0700
          Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 10:50 +0200
            Re: Serial EEPROM or Serial Flash? Reinhardt Behm <rbehm@hushmail.com> - 2018-06-15 17:03 +0800
              Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 14:59 +0200
                Re: Serial EEPROM or Serial Flash? David Brown <david.brown@hesbynett.no> - 2018-06-15 15:51 +0200
        Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 10:47 +0200
          Re: Serial EEPROM or Serial Flash? Jack <jack4747@gmail.com> - 2018-06-15 02:20 -0700
            Re: Serial EEPROM or Serial Flash? Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2018-06-15 13:41 +0200
            Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 15:01 +0200
      Re: Serial EEPROM or Serial Flash? David Brown <david.brown@hesbynett.no> - 2018-06-15 11:25 +0200
        Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 15:10 +0200
          Re: Serial EEPROM or Serial Flash? Jack <jack4747@gmail.com> - 2018-06-15 06:51 -0700
          Re: Serial EEPROM or Serial Flash? David Brown <david.brown@hesbynett.no> - 2018-06-15 16:21 +0200
            Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 17:20 +0200
              Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-15 13:11 -0400
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-15 22:54 +0200
                Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-15 18:25 -0400
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-16 08:26 +0200
                Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-16 09:20 -0400
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-16 19:38 +0200
                Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-16 16:41 -0400
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-16 23:05 +0200
              Re: Serial EEPROM or Serial Flash? David Brown <david.brown@hesbynett.no> - 2018-06-17 18:41 +0200
            Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-16 20:12 +0200
              Re: Serial EEPROM or Serial Flash? David Brown <david.brown@hesbynett.no> - 2018-06-17 19:27 +0200
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-19 17:40 +0200
              Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-17 17:05 -0400
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-19 17:44 +0200
                Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-19 23:14 -0400
                Re: Serial EEPROM or Serial Flash? pozz <pozzugno@gmail.com> - 2018-06-20 11:03 +0200
                Re: Serial EEPROM or Serial Flash? Richard Damon <Richard@Damon-Family.org> - 2018-06-20 08:03 -0400
  Re: Serial EEPROM or Serial Flash? Michael Karas <mkaras@carousel-design.com> - 2018-06-23 09:43 -0700

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