R8C/Tiny flash re-programming limits

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Hello Newsgroup,

In the data sheets of the Renesas R8C controllers some versions are
listed with lower re-programming cycles for the flash than others. Some
can be re-programmed 100 times, others 1000 times. Both numbers seem
kind of low. In your experience, is that just an extremely conservative
spec or do they really fail when these numbers are significantly exceeded?

Regards, Joerg

http://www.analogconsultants.com

Re: R8C/Tiny flash re-programming limits
On Saturday, in article

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This is something that used to be asked a lot on GNUH8 mailing list about
H8 series devices, and after announcement from Hitachi (at the time) was
down to being a WORST case guaranteed across all temperature ranges, voltage
ranges and maintaining a 10 year retention period. What was also
deterministic in this was the process used 0.35um etc..

Related H8 information

     FAQ  <http://www.gnuh8.org.uk/faq.htm

    copy of change notice

        <http://www.gnuh8.org.uk/tnmc002ae.pdf

There should be something similar around for R8 and R16, but may take
some finding.

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Re: R8C/Tiny flash re-programming limits
Hello Paul,

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Thanks, that clarifies it. I had searched for that too narrowly (in
connection with R8C) and came up dry.

I still find it a bit strange that one device is listed at 100 times
while the next in line is listed at 100 times. But that might just be
historical. And as you said in the above FAQ Renesas doesn't want to be
sued. Kind of like the printing on the side of our wheel barrow: "Not
for highway use".

Regards, Joerg

http://www.analogconsultants.com

Re: R8C/Tiny flash re-programming limits
On Saturday, in article

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I asume you mean next is listed at 1000 times.

Some of that will be down to newer processes and smaller geometry (0.35um to
0.18um etc.) also down to what testing had been done. Who wants to go back
to an old design and do the complicated testing of an old design at 60
degrees! Especially if you want to examine the die under a microscope or do
other tests to judge the data retention period.

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A bit like that and not wanting to spend time and money retesting devices
at different temperatures etc..

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Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: R8C/Tiny flash re-programming limits
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Yes, when I asked the Renesas FAE's they told me that they made
experiments and gave up after 100'000 cycles.

My developement board I used to program surely got more than 10'000
cycles - no problem encountered ever.

Markus


Re: R8C/Tiny flash re-programming limits
Hello Markus,

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That is good to know. Especially in experiments with large boards this
is important, the kind of boards you can't throw out because duplicating
them would be a lot of work. You can easily exceed 100 times on a
prototype board and the worst case would be to chase a perceived coding
error and not seeing that part of the flash has became corrupt. But it
seems that is unlikely.

Regards, Joerg

http://www.analogconsultants.com

Re: R8C/Tiny flash re-programming limits

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You do know about cheksums, right?

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Grant Edwards                   grante             Yow!  In Newark the
                                  at               laundromats are open 24
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Re: R8C/Tiny flash re-programming limits
Hello Grant,

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Yes. My concern was more about bits becoming flaky or where that
flakiness only happens upon ADC clock or when a heavily loaded output
turns on etc. That's hard to catch.

I have done lots of EMI susceptibility and ESD tests. Often a digital
system will become rather non-digital or die very gradually.

Regards, Joerg

http://www.analogconsultants.com

Re: R8C/Tiny flash re-programming limits
Quoted text here. Click to load it

I'm using the H8 series and I've never seen one fail, though I
think there's probably only one unit that's exceeded the 100
cycle limit.

Like all specs, it's probably a bit conservative, but I
wouldn't plan on being able to exceed the specs.

--
Grant Edwards                   grante             Yow!  I feel like a wet
                                  at               parking meter on Darvon!
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Re: R8C/Tiny flash re-programming limits
Hello Grant,

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In production we certainly won't. I never go above data sheet ratings.
The concern would be for the prototyping phase of large boards that have
a uC on there. 100 cycles would certainly be exceeded on those. It's a
pain when the 'golden unit' croaks an hour before a demo and all the
dignitaries are already beginning to gather in the board room.

Regards, Joerg

http://www.analogconsultants.com

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