sd_flash_page_erase on nrf52840 takes a long time

[Youssif]

Hi

We are seeing a significant delay in a flash-related operation on the nrf52840, specifically using the function sd_flash_page_erase() When we use that function to erase flash it takes up to 3 times longer on the nrf52840 than it does on the nrf52832 running the exact same code. Is this an expected behaviour/known issue?

We are using softdevice S140 v5.0.0-3.alpha, SDK v14.0.0 and the nr52840 preview development kit.

Thanks

[Sigurd]

Hi,

The behavior you are seeing is expected. We use a different type of flash on the nRF52840 than on the nRF52832. It takes a longer time to erase a page on the nRF52840, but it should be faster to write a page on the nRF52840 compared to the nRF52832.

[Youssif]

Thank you. Can you please direct me to where this is stated so that we can reference it in our code?

[Sigurd]

You have the Non-volatile memory controller(NVMC) Electrical specification here:

nRF52840: Link

nRF52832: Link

[Youssif]

From the links, nRF52840's tWRITE, tERASEPAGE, and tERASEALL (41us, 85ms, 169ms) are all shorter than nrf52832's tWRITE, tERASEPAGE, and tERASEALL (338us, 89.7ms, 295.3ms)?

[Sigurd]

The values you list here is the max values. The typically values for the nRF52832 will vary more, but will be closer to the min values listed. But for the nRF52840 the typically values will vary much less, and will be closer to the max values listed.