Flash Data Storage (FDS): What is the Page size?

[awneil]

FDS_VIRTUAL_PAGE_SIZE

The size of a virtual flash page.

Expressed in number of 4-byte words. By default, a virtual page is the same size as a physical page. The size of a virtual page must be a multiple of the size of a physical page.

Following options are available:

• 256 - 256 (nRF51 family only)
• 512 - 512 (nRF51 family only)
• 1024 - 1024
• 2048 - 2048

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.0.0/group__fds__config.html#ga94b7203878878277663b572bded3499d

So how do we know what the size of a physical page is?

I can't see any FDS API or symbolic definition that will give this - so do we just have to hard code it as a magic number?

[tesc]

Hi,

Page size for nRF51 series is 1024 bytes, and for nRF52 series is 4096 bytes. Hence the options start at 256 (words) for nRF51 family and at 1024 (words) for the nRF52 family.

You can read the page size from the CODEPAGESIZE register in FICR.

Regards,
Terje

[awneil]

Thanks. 

tesc said:

You can read the page size from the CODEPAGESIZE register in FICR.

It would be helpful if that were mentioned in the FDS documenation.

Even more helpful if it were accessible via the FDS API,  without having to faff about with low-level register access - what's the point of having a high-level API if you still need to faff about with low-level register access?!

And what is the meaning of "256 - 256", etc, in the list of options?

Why are two limits used when they're all just a single value?!

[tesc]

Hi,

I found a define FDS_PHY_PAGE_SIZE in fds_internal_defs.h, although it is not documented as part of FDS API. I have registered a feature request in our internal issue tracker.

To me the double listing of the values looks like an artifact from the format of sdk_config.h entries. It certainly does not look right and I have registered an isuse internally for that one as well.

Regards,
Terje

[awneil]

Great - thanks.

[awneil]

tesc said:

You can read the page size from the CODEPAGESIZE register in FICR.

and is that value in bytes or words?

The linked page doesn't say!