Nrf52 flash programming : 'writes in a block between erase'

RE: Nrf52 flash programming : 'writes in a block between erase'

Mahendra Tailor — Fri, 03 Feb 2017 17:39:17 GMT

I asked and the definitive answer about how many times one can write to a dword is as per the following response I got ...

The real limitation is that you can write up to 8 times to the same address, as long as you don't touch other 32-bit words inside the same 128-bit block. For simplicity we have stated in the product specification that the maximum is 2 writes for a 32-bit word. The limitation should be considered hard as breaking it may result in bits being flipped.

So I asked a follow on question about the address boundary of that 128 bit block and the answer was ...

I can confirm that the start addresses of the 128 bit blocks are those addresses which are divisible by 16.

I think I can manage to develop I driver to atomically write a multidword object and still be able to detect an interruption on next power up.

RE: Nrf52 flash programming : 'writes in a block between erase'

Mason — Thu, 26 Jan 2017 16:08:25 GMT

Section 8.2 in the v1.2 spec sheet states, "Each Page is divided into 8 blocks." Taking that into account, It seems that you can safely write each word once in a page (128 words per block, 8 blocks per page), plus a bit more.

The datasheet is a bit vague with this, and it would be nice to get some clarification from Nordic on this question.

RE: Nrf52 flash programming : 'writes in a block between erase'

pytepaul — Mon, 23 Jan 2017 17:17:47 GMT

Hi RK,

Do you mean 181 writes at any address of the page or of the block ? Spec says "Amount of writes allowed in a block between erase", but I am confused about nordic's use of page and block. Usually in NAND datasheet a block is made of page, this is reversed in NRF52 chip. But on the block protection module a block is defined as a 4KB unit, which is the size of the page on the memory layout, while the block is 512B.

I have some understanding doubts about this 181 write spec as a block is said as 512B while writing 181 times one word is 724B. So limitation appply for bit to bit writing only...

So is it 181 write in the same block or in the whole page?

Thanks,

RE: Nrf52 flash programming : 'writes in a block between erase'

RK — Sun, 17 Jan 2016 12:11:30 GMT

yeah I have one of those too - I keep state in a 32 bit word and drop a bit each time I move from one state to another, it's very useful. That lets me mark blocks as allocated, then in-use, then dropped etc, kind of like a filesystem.

RE: Nrf52 flash programming : 'writes in a block between erase'

Mahendra Tailor — Sun, 17 Jan 2016 12:09:27 GMT

Phew!! That is a relief. Thank you very much for explanation. I have developed a flash file system and it can result in writes often, potentially up to 32 times as I drop a bit to 0 for a mechanism to write atomically to a block of words multiple times

RE: Nrf52 flash programming : 'writes in a block between erase'

RK — Sun, 17 Jan 2016 11:35:33 GMT

Section 10.1 "The same block address in the NVM can only be written nWRITE number of times before an erase must be performed using PAGEERASE , ERASEUICR, or ERASEALL."

nWrite is a minimum of 181. So you can write any address in the page 181 times at a minimum before you have to erase the page. Not that that would be very useful as you can only change it a maximum of 32 times before you have all bits set to zero.

I assume the 181 times includes times you write it but don't actually change anything, else it really would be meaningless.

Basically not much of a restriction.