Re: Serial EEPROM or Serial Flash?

From	Reinhardt Behm <rbehm@hushmail.com>
Newsgroups	comp.arch.embedded
Subject	Re: Serial EEPROM or Serial Flash?
Followup-To	comp.arch.embedded
Date	2018-06-15 17:03 +0800
Organization	A noiseless patient Spider
Message-ID	<pfvvcd$5ao$1@dont-email.me> (permalink)
References	(1 earlier) <pfth8a$vpp$1@dont-email.me> <pfvqei$9t7$1@dont-email.me> <8bdfea77-13fc-462a-a01a-d7cd97e9d6c6@googlegroups.com> <pfvt7v$l9u$1@dont-email.me> <pfvuke$uha$2@dont-email.me>

Followups directed to: comp.arch.embedded

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AT Friday 15 June 2018 16:50, pozz wrote:

> Il 15/06/2018 10:26, Reinhardt Behm ha scritto:
>> AT Friday 15 June 2018 15:54, Jack wrote:
>> 
>>> Il giorno venerdì 15 giugno 2018 09:39:03 UTC+2, pozz ha scritto:
>>>
>>>> Why do I need checksum?  The only thing that comes in mind is to
>>>> prevent writing errors: for example, I want to write 0x00 but the value
>>>> really written is 0x01, maybe for a noise on the serial bus.
>>>>
>>>> To solve this situation, I need checksum... but also I need to re-read
>>>> and re-calculate the checksum at *every* area writing... and start a
>>>> new writing if something was wrong.
>>>
>>> At power up, when you read Area1 (for example) how do you know that the
>>> data are not corrupted (even if magic/counter are correct)?
>>>
>>> Bye Jack
>> 
>> How can he know if the write was successful and not aborted midway
>> because of a power interruption.
> 
> Because of the counter that is written as the last byte.  If the write
> has interrupted, the counter of the new area contains an old value, so
> at startup is loaded old area.
> 
>> With those flash devices who have their "own life" you don’t even have a
>> guaranty that things get written in the same sequence as the software
>> thinks. So writing the "magic" after the data to make sure it signals
>> updated data does not guaranty that physically it gets written before the
>> data.
> 
> I can't follow your arguments... if I send write commands in a sequence,
> how the data could be written with a different sequence?

If this is a flash device with an internal controller that does the 
blocking/unblocking for you - meaning to change a single byte it reads a 
block, changes the byte, erases the block and writes the block - it has its 
own life. You must know that it does not cache things and "optimizes" writes 
by reordering them. Some flash drives are just doing this.
If it is a dump device then you are on the save side. But you must make 
sure.
With the usual EEPROMs (like the small 8-pin I2C devices) you are on the 
save side. They are dump. But I would never trust these flash chips without 
having a clear specification from the manufacturer about how they work. Some 
manufacturers do strange things to get nice "performance" numbers for 
marketing.

-- 
Reinhardt

Thread

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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