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Default value in EEPROM 24XX series

Started by diptipanchal July 23, 2008
We are using 24XX series EEPROM of microchip make. I have read the data from
the EEPROM (without writing data to EEPROM), it always give as 0xFF. Atleast
i have checked in 5 EEPROM.

In the datasheet, it is not mentioned what should be the default value?

Could anyone let me know what should be the default value in EEPROM.

-
Dipti
--

Beginning Microcontrollers with the MSP430

Non-volatile memory like EEPROM always comes in the 'erased' state IOW 0xFF.
So, this is normal in your EEPROM.
AFAIK the only exception is large NAND flash, which can/will have bad sector
markers.

HTH
-- Kris

-----Original Message-----
From: m... [mailto:m...] On Behalf Of
diptipanchal
Sent: Wednesday, 23 July 2008 4:46 PM
To: m...
Subject: [msp430] Default value in EEPROM 24XX series
We are using 24XX series EEPROM of microchip make. I have read the data from
the EEPROM (without writing data to EEPROM), it always give as 0xFF. Atleast
i have checked in 5 EEPROM.

In the datasheet, it is not mentioned what should be the default value?

Could anyone let me know what should be the default value in EEPROM.

-
Dipti
--

In my application, based on this default value of the EEPROM, its gonna
perform some 'X' task. If in future this default value i.e. 0xFF would
change then my application won't perform 'X' task. That is why I want to
be 100% sure whether it has to be 0xFF or not.

Just a doubt, If it comes in erased state why datasheet does not mention
about it ??

--

Dipti

________________________________

From: m... [mailto:m...] On Behalf
Of Microbit_P43000
Sent: Wednesday, July 23, 2008 12:33 PM
To: m...
Subject: RE: [msp430] Default value in EEPROM 24XX series

Non-volatile memory like EEPROM always comes in the 'erased' state IOW
0xFF.
So, this is normal in your EEPROM.
AFAIK the only exception is large NAND flash, which can/will have bad
sector
markers.

HTH
-- Kris

-----Original Message-----
From: m...
[mailto:m... ] On
Behalf Of
diptipanchal
Sent: Wednesday, 23 July 2008 4:46 PM
To: m...
Subject: [msp430] Default value in EEPROM 24XX series

We are using 24XX series EEPROM of microchip make. I have read the data
from
the EEPROM (without writing data to EEPROM), it always give as 0xFF.
Atleast
i have checked in 5 EEPROM.

In the datasheet, it is not mentioned what should be the default value?

Could anyone let me know what should be the default value in EEPROM.

-
Dipti
--




2008/7/23 :

> In my application, based on this default value of the EEPROM, its gonna
> perform some 'X' task. If in future this default value i.e. 0xFF would
> change then my application won't perform 'X' task. That is why I want to
> be 100% sure whether it has to be 0xFF or not.
>
> Just a doubt, If it comes in erased state why datasheet does not mention
> about it ??
>
> --
>
> Dipti
>
> It does not mention it because, while it is normal for the device to be in
its erased state it is not normally guaranteed, so relying on this for your
device operation is a somewhat risky strategy. If you must have some magic
value in a given location then it is up to you to put it there.

Ian

----- Original Message -----
From:
To:
Sent: Wednesday, July 23, 2008 09-24
Subject: RE: [msp430] Default value in EEPROM 24XX series
>
> In my application, based on this default value of the EEPROM, its gonna
> perform some 'X' task. If in future this default value i.e. 0xFF would
> change then my application won't perform 'X' task. That is why I want to
> be 100% sure whether it has to be 0xFF or not.
>
> Just a doubt, If it comes in erased state why datasheet does not mention
> about it ??
> Dipti
> ________________________________
> From: m... [mailto:m...] On Behalf
> Of Microbit_P43000
>
> Non-volatile memory like EEPROM always comes in the 'erased' state IOW
> 0xFF.
> So, this is normal in your EEPROM.
> AFAIK the only exception is large NAND flash, which can/will have bad
> sector
> markers.
And also: the very nice pin-compatible FRAM chips from Ramtron (100 ns R/W
time, and almost infinite write operations allowed) just happen to come with
a somewhat random 0x00 - 0xFF pattern.

Don't ever trust an initial state - program it explictly in production,
maybe using some special 'init' command in the application.

Arie de Muynck
Thanks for all your inputs....

--

Dipti

________________________________

From: m... [mailto:m...] On Behalf
Of Arie de Muijnck
Sent: Thursday, July 24, 2008 1:45 AM
To: m...
Subject: Re: [msp430] Default value in EEPROM 24XX series

----- Original Message -----
From: >
To: >
Sent: Wednesday, July 23, 2008 09-24
Subject: RE: [msp430] Default value in EEPROM 24XX series

>
> In my application, based on this default value of the EEPROM, its
gonna
> perform some 'X' task. If in future this default value i.e. 0xFF would
> change then my application won't perform 'X' task. That is why I want
to
> be 100% sure whether it has to be 0xFF or not.
>
> Just a doubt, If it comes in erased state why datasheet does not
mention
> about it ??
> Dipti
> ________________________________
> From: m...
[mailto:m... ] On
Behalf
> Of Microbit_P43000
>
> Non-volatile memory like EEPROM always comes in the 'erased' state IOW
> 0xFF.
> So, this is normal in your EEPROM.
> AFAIK the only exception is large NAND flash, which can/will have bad
> sector
> markers.

And also: the very nice pin-compatible FRAM chips from Ramtron (100 ns
R/W
time, and almost infinite write operations allowed) just happen to come
with
a somewhat random 0x00 - 0xFF pattern.

Don't ever trust an initial state - program it explictly in production,
maybe using some special 'init' command in the application.

Arie de Muynck


Good point. I would rely on a unique signature, like 4-6 bytes long.
At reset, check for that signature in EEPROM - if not there, it's a default
device. I always use this principle in RAM to work out whether an MCU is in
cold or warm start.

B rgds
Kris

-----Original Message-----
From: m... [mailto:m...] On Behalf Of
Arie de Muijnck
Sent: Thursday, 24 July 2008 6:15 AM
To: m...
Subject: Re: [msp430] Default value in EEPROM 24XX series
----- Original Message -----
From:
To:
Sent: Wednesday, July 23, 2008 09-24
Subject: RE: [msp430] Default value in EEPROM 24XX series
>
> In my application, based on this default value of the EEPROM, its gonna
> perform some 'X' task. If in future this default value i.e. 0xFF would
> change then my application won't perform 'X' task. That is why I want to
> be 100% sure whether it has to be 0xFF or not.
>
> Just a doubt, If it comes in erased state why datasheet does not mention
> about it ??
> Dipti
> ________________________________
> From: m... [mailto:m...] On Behalf
> Of Microbit_P43000
>
> Non-volatile memory like EEPROM always comes in the 'erased' state IOW
> 0xFF.
> So, this is normal in your EEPROM.
> AFAIK the only exception is large NAND flash, which can/will have bad
> sector
> markers.
And also: the very nice pin-compatible FRAM chips from Ramtron (100 ns R/W
time, and almost infinite write operations allowed) just happen to come with

a somewhat random 0x00 - 0xFF pattern.

Don't ever trust an initial state - program it explictly in production,
maybe using some special 'init' command in the application.

Arie de Muynck