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I have a question regarding F-RAM I will be using the Cypress FM16W08 as an example. Here is a link to the datasheet: http://www.cypress.com/file/41731/download

I have recently used it as a drop in replacement for a Dallas DS1225 battery backed S-RAM that holds the calibration constants in a lab power supply. I was able to read the old S-RAM and dump the contents into the new F-RAM and it's working perfectly.

One thing confuses me though. It is my understanding that when a certain address in F-RAM is read the data at that address is lost. While in S-RAM the data remains after a read.

Since the equipment was not designed with F-RAM in mind and it's not writing the data back since it was designed to use S-RAM. Am I correct in assuming that F-RAM has internal circuitry to automatically write back to itself after a read?

On page 4 of the datasheet under the heading Endurance. I believe it vaguely refers to this operation as "a read and restore mechanism" but I'm not sure.

Thanks For Your Time.

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  • \$\begingroup\$ Have you checked to make sure your device is compatible with the requirements for CE as shown on page 5 figure 2? \$\endgroup\$ – Tom Carpenter Jul 25 '15 at 18:29
  • \$\begingroup\$ Yes the device is strobing CE properly and is compatible. \$\endgroup\$ – Krankshaft Jul 25 '15 at 19:16
  • \$\begingroup\$ Ah, sorry, misread the question as there being a problem with the data. Never mind. \$\endgroup\$ – Tom Carpenter Jul 25 '15 at 20:59
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It is my understanding that when a certain address in F-RAM is read the data at that address is lost. While in S-RAM the data remains after a read.

Correct. Reading from a ferroelectric cell involves forcing the ferroelectric material to a given polarity and seeing if any electrical excitation occurred from the change, as opposed to reading from a SRAM cell which involves redirecting a minute amount of current from the latch.

Since the equipment was not designed with F-RAM in mind and it's not writing the data back since it was designed to use S-RAM. Am I correct in assuming that F-RAM has internal circuitry to automatically write back to itself after a read?

Also correct. F-RAM ICs from Ramtron/Cypress are intended to be drop-in replacements for SRAM ICs, and this can only be done if the IC itself contains the circuitry to restore the value stored in the cell before reading.

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