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274 Views 5 Replies Last post: Feb 3, 2010 7:28 AM by ckgrier RSS
ajith2383 Newbie
ajith2383
14 posts since
Feb 3, 2010
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Feb 3, 2010 2:54 AM

Data Flash : Is overwrite possible without erasing?

I'm using the R8C35. Is it possible to overwrite any memory location in dataflash which is used without erasing.

FrankL Apprentice
FrankL
1,100 posts since
Mar 16, 2009
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Feb 3, 2010 4:40 AM in response to: ajith2383
Re: Data Flash : Is overwrite possible without erasing?

It is possible to change bits from "1" to "0". It is not possible to change bits from "0" to "1".

And it is not recommended to write bits to "1" more than once.

So, the answer is no.

ajith2383 Newbie
ajith2383
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Feb 3, 2010
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Feb 3, 2010 4:49 AM in response to: FrankL
Re: Data Flash : Is overwrite possible without erasing?

Thank you Frank for the reply.

Can you please comment on the endurance of dataflash. How the life of datflash decreases?. Its understood from manual that it has 10K endurance cycle.

Does it decrease by one for every erase or for every write?

FrankL Apprentice
FrankL
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Mar 16, 2009
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Feb 3, 2010 5:16 AM in response to: ajith2383
Re: Data Flash : Is overwrite possible without erasing?

The endurance counts erase-write cycles. It does not assume that a single cell is written more than once without erasing. Writing cells more than once without erase can decrease the number of possible erase-write cycles.

ajith2383 Newbie
ajith2383
14 posts since
Feb 3, 2010
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Feb 3, 2010 6:23 AM in response to: FrankL
Re: Data Flash : Is overwrite possible without erasing?

Frank,

 

Let me put my doubt bit detailed way. My basic idea is to replace the EEPROM with DataFlash, I wanna write 16bytes to Dataflash everytime a particular event occurs.

I'm planning to write it sequenctially, 0-15(run-1), 16-31(run-2)...so on..,and once i reach (4K) boundary, I Erase alll the blocks. So my doubt is, here, the erase-write cycle count is reduced by one only

we erase it. Is my understanding right?

 

Please help in this regard.

ckgrier Apprentice
ckgrier
840 posts since
Mar 16, 2009
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Feb 3, 2010 7:28 AM in response to: ajith2383
Re: Data Flash : Is overwrite possible without erasing?

There's actually a very good discussion of this topic in the application note we provide with the Renesas Flash API. Look in the "most downloaded" list at the bottom of this page. The Flash API is #1!

http://america.renesas.com/fmwk.jsp?cnt=software_landing.jsp&fp=/support/software/

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