SPI Serial EEPROM design

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Hello:

I'm starting up a new desing using 4 Atmel AT25HP512 devices connected
to a 4 wire SPI interface.

My question is does anyone have an over view (pseudo code) of hew to
        Initialize
        Read
        Write Enable
        Write

These devices.  I've got all the C code writen but I'm missing
something

Thanks In Advance.
George


Re: SPI Serial EEPROM design
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Doesn't the data sheet explain it?  

I'm using Atmel IIC EEPROMs at the moment, so I don't have the
SPI version data sheets handy, but the last time I used Atmel
SPI EEPROMs, the data sheet explained exactly what you needed
to do.

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Grant Edwards                   grante             Yow!  "THE LITTLE PINK
                                  at               FLESH SISTERS," I saw them
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Re: SPI Serial EEPROM design

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It helps to have a logic analyzer hooked up
so that you can check your signals against
the datasheet.


Re: SPI Serial EEPROM design

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A 4-channel digital scope will works just as well.  A 2-channel
scope is a bit more cumbersome, but will do in a pinch.

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Grant Edwards                   grante             Yow!  I wonder if I ought
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Re: SPI Serial EEPROM design
Well I'm more stuck in how to unlock the device.
It powers up with writes disabled.
I've read the data sheets and it metions that I need to set the control
register and issue a write enable command.
But the details are vague.  And the order of these in not at all clear.

These are relative new devices so perhaps I should look at the previous
versions data sheet for clues.

george


Re: SPI Serial EEPROM design
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1) make sure you have the /WP pin pulled or strapped to VCC.
2) send WRSR,0 to enable writing to all blocks (BP0,1).
3) send the WREN instruction. that sets the WEN bit in the status reg.

you can read the status reg to see if is setup correctly. BP0,1 should
all be low to write-enable all blocks. WEN should be high to enable writing.

Hope that helps.

  - Richard



Re: SPI Serial EEPROM design
I think I'm doing this but...

To write enable the devices, should I do a WREN (write enable 8 bit
command)  then WRSR (write Status Reg 16 bit command) or in the
opposite order?

I don't always see the WEN bit set in the statyus registers?????????
Some days yes today no.

I can see the status going busy after the above sequence.

I read all ones.

THanks
george


Re: SPI Serial EEPROM design
SST have similar SPI parts.

SST25xxxx

There is example C code commands available from
http://www.sst.com/products.xhtml/serial_flash /

Here's the driver
http://www.sst.com/downloads/software_driver/SST25VFxxx.txt

JG

www.sst.com
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Re: SPI Serial EEPROM design
Also check out

http://www.sst.com/downloads/app_note/S72051.pdf


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Re: SPI Serial EEPROM design
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Forgive me for being slightly off topic but have you not thought about
replacing the eeprom with serial flash ?

Regtards
Spen



Re: SPI Serial EEPROM design
These EEPROMs store system information and are constantly changing.  So
I need the 100K writes of EEPROM.

What is Serail FLASH???

george


Re: SPI Serial EEPROM design
snipped-for-privacy@att.net says...
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If you need lots of frequent updates, you might investigate the
SPI Ferro-Electric RAM  (FRAM) from RAMTRON.

Mark Borgerson



Re: SPI Serial EEPROM design
I found my problem.
THis device only supports 128 byte writes.  One needs to get to a 128
byte boundary and then send 128 bytes of data.  Unsent bytes will be
undefined.

Actually Atmel support guided me through all this.  Good Job Atmel.

And thanks to all who replied.

gm


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