nRF52: Write/erase flash cycles confusion

RE: nRF52: Write/erase flash cycles confusion

vit bernatik — Wed, 24 Aug 2016 14:18:33 GMT

According to devzone.nordicsemi.com/.../ your answer is not correct...

RE: nRF52: Write/erase flash cycles confusion

vit bernatik — Wed, 24 Aug 2016 13:57:20 GMT

I do not understand your answer. The write is by 4B. The smallest block that can be erased has 0x200 B. So in order to fill it after erase you would need erase + 128 times write. I'm quite sure that these 128 times of write won't count as 128 "endurance cycles". To my understanding erase + 128 times write is one endurance cycle. The question is how it is counted when you write to same word. In datasheet nRF52832_PS_v1.1 is written that Amount of writes allowed in a block between erase is up to 181. So I assume one endurance cycle is even more -> 1 erase + 181 writes. And of course you can not write more times without erase. As I understand if you write more you risk that some of "1" that you did not try to clear can be cleared unintentionally.

RE: nRF52: Write/erase flash cycles confusion

ThierryQ — Tue, 16 Aug 2016 08:06:35 GMT

Got it, thank you for your reply.

So regarding my scenario, I will consume 2 cycles in worst case (1/10000 for erase and 2/10000 for write).

BR, Thierry.

RE: nRF52: Write/erase flash cycles confusion

Hung Bui — Tue, 02 Aug 2016 12:47:48 GMT

@Thierry: Our confirmation is that one cycle includes one erase and one write. So 10000 erase/write cycle mean you can do 10000 erase and 10000 write.

RE: nRF52: Write/erase flash cycles confusion

ThierryQ — Thu, 28 Jul 2016 15:44:55 GMT

Thank you for your quick reply.

Someone else can confirm: write action will not impact the flash cycle (Only erase will do that) ?

I need to be very careful regarding this information, my product will fully dependends to it. I need to write during 3 years on this flash and the frequency of it will be directly determined by this information.

Thierry

RE: nRF52: Write/erase flash cycles confusion

sidekick — Thu, 28 Jul 2016 13:57:21 GMT

Okay, i checked the nrf52 product spec, and as you mentioned, it is indeed 10,000. I thought, the main flash ROM would have similar endurance, as some of the external serial flash memory.

RE: nRF52: Write/erase flash cycles confusion

sidekick — Thu, 28 Jul 2016 13:45:10 GMT

Without looking at the spec, my quick reply is that in general, you need to consider the erase limit. So in your case, it is 1. Note that, you might still get correct result (a read from an address returns the most recent write on that address) even after exhausting the erase limit, however the flash vendors do not guarantee that. Also, I don't think the limit would be 10000, that's quite low endurance, it should be around 100000 or more.