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'[EE]: Flash endurance'
2002\08\05@005111 by Jinx

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I need 512k x 8 storage space which can be done with a single
29C040A Flash. The quoted figure for Flash is > 10,000 write
cycles. I "might" have a look at battery backed-up SRAM, I've a
few 8M TSOPs, but truly NV is preferable

Does the endurance refer to the number of times a bit changes
state or the number of times that bit is written to, whether it
changes state or stays the same ? As the PIC's Flash memory
can be re-programmed ~1,000 times that makes me wonder.
Could that be Microchip's definition of > 10,000, ie 14 bits x 1,000 ?

If, (as I think because the 29C040A data doesn't say otherwise),
it means each sector can be over-written 10,000 times however
the contents change, then I'm OK, else I'll go with 8 x 24C512
EEPROM (> 10,000,000 writes but more board and 3x the price)

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2002\08\05@010927 by Brent Brown

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On 5 Aug 2002 at 16:49, Jinx wrote:
> Does the endurance refer to the number of times a bit changes
> state or the number of times that bit is written to, whether it
> changes state or stays the same ?

I think with Flash you can't re-write anything, you need to erase it
first. Some let you erase just a single byte, others a page, still
others the whole chip. Does that make it easier or harder?



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2002\08\05@014335 by Jinx

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> I think with Flash you can't re-write anything, you need to erase
> it first. Some let you erase just a single byte, others a page, still
> others the whole chip. Does that make it easier or harder?

The 29C040A does an automatic erase before write, so that's
covered. It also has a small sector size of 256 bytes (2048 of
them), which is about all you can load into an F877. As far as I
can see, the smallest sector size in a "large" Flash memory is
64 bytes. It's a read-modify-write operation - you have to load the
sector into the PIC, modify it and then write it back as a whole
sector (AFAIK). Other Flash chips have very large sectors that
need a separate SRAM to copy them into, and the erasure of
those large sectors when writing back can take some time (many
seconds), whereas small sectors can be modified in a few 10's
of ms

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2002\08\05@021113 by Brent Brown

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My guess then is that the endurance is the number of times a location
can undergo the read/write procedure, I would count 1 for each
read/modify/write even though there are 2 steps in the process. Worst
case you will be out by a factor of 2?

Have looked at some Samsung SmartMedia chips recently and they say
less than 0.1% failure in 1 million program/erase cycles. I think the
idea is it's anyones guess when they actually fail and you need to
take this into account with bad block mangement.

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2002\08\05@030222 by Wouter van Ooijen

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> The 29C040A does an automatic erase before write, so that's
> covered. It also has a small sector size of 256 bytes (2048 of
> them), which is about all you can load into an F877. As far as I
> can see, the smallest sector size in a "large" Flash memory is
> 64 bytes. It's a read-modify-write operation - you have to load the
> sector into the PIC, modify it and then write it back as a whole
> sector (AFAIK). Other Flash chips have very large sectors that
> need a separate SRAM to copy them into, and the erasure of
> those large sectors when writing back can take some time (many
> seconds), whereas small sectors can be modified in a few 10's
> of ms

I guess you have been reading too much of the ..A or 18F... Datasheets.
The 16f87* (without A!) can write a single instruction (14 bits) at a
time.

Wouter van Ooijen

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PICmicro chips, programmers, consulting

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2002\08\05@044813 by Jinx

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>16f87* can write a single instruction (14 bits) at a time.

Hi, yes it can. I was speculating on why PIC flash appears to
have 1/10th of the write cycle endurance of other flash (which
is called RAM, rather than "program memory")

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2002\08\05@084603 by Bob Ammerman

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I would consider FRAM (ferroelectric ram) devices in lieu of FLASH.

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Brent Brown" <brent.brownspamKILLspamCLEAR.NET.NZ>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Monday, August 05, 2002 2:08 AM
Subject: Re: [EE]: Flash endurance


{Quote hidden}

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2002\08\05@094229 by Jinx

face picon face
>FRAM (ferroelectric ram) devices in lieu of FLASH

http://www.ramtron.com/aboutfram/aboutfram.htm

Might do for a future product but for the present I can't see one
bigger than 256k, which is a long way short of the 4M I need.
I have no idea who the local supplier would be to ask - what's
the price like ?

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2002\08\05@113638 by Bob Ammerman

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Ah, I missed the capacity requirement.

Not sure where to get them (check distributors on Ramtrom stite?).

No idea of price.

I submitted a request for samples >2 weeks ago. So far, nothing.

Bob Ammerman
RAm Systems


{Original Message removed}

2002\08\05@181702 by Brent Brown

picon face
On 6 Aug 2002 at 1:41, Jinx wrote:
> >FRAM (ferroelectric ram) devices in lieu of FLASH
>
> http://www.ramtron.com/aboutfram/aboutfram.htm
>
> Might do for a future product but for the present I can't see one
> bigger than 256k, which is a long way short of the 4M I need. I have
> no idea who the local supplier would be to ask - what's the price like

I have some sample FM24CL64 and FM25CL64's from this place:

Non Volatile Technologies
http://www.nvtech.com.au
Ph: 0061 2 9540 9027
Fax: 0061 2 9540 9017
23 Avenel Road
Gymea Bay NSW
2227 Australia

Customer gave me the samples so I don't know the price, much less
than NZ$10ea anyway.
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Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  brent.brownspamspam_OUTclear.net.nz

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2002\08\05@182249 by Jinx

face picon face
> I have some sample FM24CL64 and FM25CL64's from this place:
>
> Non Volatile Technologies
> http://www.nvtech.com.au
> Ph: 0061 2 9540 9027
> Fax: 0061 2 9540 9017
> 23 Avenel Road
> Gymea Bay NSW
> 2227 Australia

Cheers, I'll look into it. From my Google search it appears many
of the large manufacturers have either got Ramtron licences or
are designing their own. I expect FRAM will be as common and
cheap as SRAM shortly

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2002\08\06@060656 by Alan B. Pearce

face picon face
>I need 512k x 8 storage space which can be done with a single
>29C040A Flash. The quoted figure for Flash is > 10,000 write
>cycles. I "might" have a look at battery backed-up SRAM, I've a
>few 8M TSOPs, but truly NV is preferable

You may like to look at the maxim/Dallas DS1251 which is a 512k byte battery
backed SRAM with phantom clock. Appreciate you don't need the clock, and it
does not take address space. Comes in 32 pin dip or 34 pin powercap formats.

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2002\08\06@175844 by Jinx

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> You may like to look at the maxim/Dallas DS1251 which
> is a 512k byte battery backed SRAM with phantom clock

Nice idea Alan but............

I'd priced the DS1245 (1M) previously at $51 inc tax so I had
an inkling of what to expect in the way of cost. As of this morning
the DS1251 at Arrow is $271 inc tax, MOQ 10 pieces, 5 month
lead time. With all due respect, I'll pass on that thank you

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2002\08\07@045359 by Alan B. Pearce

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>Nice idea Alan but............

Yeah, OK, I can see that those prices would make one gasp a bit.

Oh well it might be back the 64256 chips then :)

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