what's the typical flash erase and write time on nRF52840?

[weifeng li]

Hi there,

I found the FW swap time in Mcuboot is too long. debugging into the code, the function, boot_move_sector_up, take ~20s, my FW is ~600k. It means the flash erase and write time is about the max time in the datasheet. But the datasheet doesn't provide a typical time, is there anyone can provide the typical time?

Thank you.

[Benjamin]

Hi,
We only specify maximum flash erase/write times in the nRF52840 datasheet, not typical values. Only the worst-case is guaranteed. In practice, most devices perform faster than the max spec, but there is no official "typical" number published. If you need more precise estimates, you’ll need to some benchmarking.

I did a very simple (and bad) benchmark with nrfutil program. It includes some overhead but you can see that we get write speeds under 28 us per word.

[weifeng li]

HI Benjamin,

Thank you very much on the benchmark.

Can you provide the same benchmark on flash erase?

[Benjamin]

Doing a benchmark like that doesn’t make much sense as the overhead is large, and I’d recommend you stick to the official documentation instead as it provides the guaranteed and tested timing values.

[weifeng li]

My test of the flash erase time is just around the max time. Is there any configuration to make it more effecient?

[Benjamin]

I don't think so, to faster way to erase is to erase everything at once and not page by page. The erase time is the "max" time, that is why there is no min or typical value.