"Small" external sram for AVR

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MORA99
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#1
Posted by MORA99: Thu. Oct 8, 2009 - 02:55 PM
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Since I have now used the good part of a week getting a 23K256/640 running (with no success), I need to find an alternative.

I need 3kByte or more external ram.
SPI seems to be the interface for speed (up to 8MHz with the Atmega128 running at 16MHz).
I know about the external ram option and has used it before, there is just not room on the board for a latch and ram, and I only need 3-6kBytes.

I2C eeprom will be much too slow, taking several ms to write the data, and eventually failing, I dont need to retain the data without power.

The smallest mega with 4kb is 64pins, so thats not really an option either.

Price max 10$ in QTY 10.
I would prefer a 8-16pins chip, is there anything outthere thats fits the bill ? :)

Tags:

Learning and Information, General Electronics, ATmega128
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jayjay1974
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Posted by jayjay1974: Thu. Oct 8, 2009 - 04:41 PM
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Only MicroChip seems to make them, like the 23K640, but you already tried them but failed (miserably?).

Glancing at the datasheet they seem very easy to use. Send one byte instruction, send two byte address, receive one byte of data or send one byte of data.

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MORA99
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Posted by MORA99: Thu. Oct 8, 2009 - 04:45 PM
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Yes I posted at the bottom of this thread with my 23Kxxx progress, or lack thereof.
https://www.avrfreaks.net/index.p...

It does seem easy, and I have been over the datasheet again and again, looking at their drawings of the signal to guess the modes for the SPI.
I have interfaced at least 10 different I2C chips, all with a breeze, but SPI is giving me troubles, atleast with this chip.

Maybe the problems is in the levels used, or the pullups, or the SPI mode.

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