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This is my weekend toy, a Spansion/Cypress fl256saif00 (S25FL256S), a 32MB SPI module. This chip is salvaged from a Cisco EPC3928 Docsis 3.0 Modem Router (2012).


S25FL256S on breakout board


The (first) challenge was to be able to remove it from the donor PCB without damage it and to solder it on a breakout board, just for practice. This seems to be successful so far, nice result. Pretty good for just a first-timer. Because of this result, I just thinking of reusing it with use of a MCU.


I have downloaded the datasheet (it is huge!) and also found a library to create a filesystem on it. However, there are some questions, because this chip is not new and there are several memory protection methods described in the datasheet. I cannot figure out whether it is temporary (active when used inside application) or permanent (forever). For example write protection on some memory areas. I will spend some time on it and want to know for sure, that is not unusable by protection (thus a waste of time), for example impossible to reformat and write data/files to it. It must be fun, no frustration ;-)


So my question/doubts (before I start this investigation/journey) are:

  • Is it possible when it is protected to unlock the protection by reformat/clear the whole flash memory? Can I reuse it anyway?
  • In the datasheet, there are several packages, except mine (see picture above). There is a 16-lead SOIC displayed that match the pins however not the size (width), is this actually the same?

Datasheet references:

The datasheets, there are two versions of the same, one branded Spansion and one branded Cypress. I have read that Cypress bought Spansion in 2015, that's the reason there are two brandnames involved. I think I must use the first one, since the IC is labeled with the brand "Spansion" and module is of a device of 2012.

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  • \$\begingroup\$ It looks like if the password protection is set, there is no way to erase it or disable it. This means that you wont be able to write any data. \$\endgroup\$ – BeB00 Apr 6 '18 at 23:10
  • \$\begingroup\$ See comment at your answer. \$\endgroup\$ – Codebeat Apr 7 '18 at 0:34
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From comment: If the Password Protection is set, there is no way to remove it or change the password, as detailed on page 63 of the cypress doc

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  • \$\begingroup\$ Thanks for pointing out, read it take some time, skip the whole idea. As far I can understand, the both versions explain later on (with use of many words and differently) that you can protect it, by: - boot code (optional) - permanent setting and cannot be changed. I think Cisco will go for the last one so they use a password (to be able to flip the ppb-flag to 1) to be able to update the firmware. I don't think it is worth to spend hours on this and hopefully suspect they did by boot code. Besides, it is kinda strange the chip only supports protection on writing. \$\endgroup\$ – Codebeat Apr 7 '18 at 0:29

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