How can a 51822 QFAB have more than 128kb?

[Flagada15]

Hi all!

I recently ordered BLE tag with nrf51822 QFAB chips.

When I read back the memory content (with mem8 jlink command) I manage to read up to the address 24A60 which means 150112 bytes.

So my question is how can it be possible to have more than 128kb in a QFAB chip? I am wrong somewhere?

Thanks in advance for your answer

[psharma]

I am not a Nordic employee, so I cannot say for sure, but I would thank that chips are all made the same, and stamped according the QA test. So If the flash of a sample from a particular batch of silicon tested between 128kb and 256kb, the entire batch was stamped as AB. Hence the chip you have at hand may be a part of such a batch, and may have more flash than specified. A similar case may also be true with AA and AC variants where the AA were found to be usable with less that 32kb of RAM stable, so they were marked as 16kb RAM variant.

That's my wild guess based on the fact t hat a similar thing was done with the Atmega microcontrollers, where those ICs that were not stable at the full 16MHz were stamped with L, marking them as low power variant, and specifying their rated max speed at 8MHz. Even though those chips may do well even at 5V 16MHz.

Please correct me, of course, if I am wrong.

[Flagada15]

Thank you for your answer this sound good to me :) But on the other side I also have QFAB chips that stops exactly at 1FFFF (128kb) So it seems that some chips are made to be "true" QFAB with exactly 128kb and others were intended to be QFAA but where "downgraded" to QFAB after the tests. Is that correct you think?