Data Store

[gaetanoi]

Hi,

I store application data in arbitrary data objects (type 3 0xF1D0-0xF1DB), I'm not clear if I can modify only few bytes inside a slot without erase the slot (140 bytes).
What happens if power loss occur while write command is executing? are the old data retained?

regards
Gaetano

[ayushev]

Hi @gaetanoi

you can define how would you like to write data into the object, either overwrite completely or only partially.
optiga_util_write_data() fnction has a parameter write_type which can be either OPTIGA_UTIL_WRITE_ONLY or OPTIGA_UTIL_ERASE_AND_WRITE, the latter one will erase the object and then write your newly provided data, the first one will simply write over existing data.

[gaetanoi]

Hi @ayushev

Thank you for your reply,

What happens if power loss occur while write command is executing? are the old data retained?

regards
Gaetano

[ayushev]

In general data is updated atomically, but there is a nuance:
If it is using SetDataObject (optiga_util_write_data()) -> up to maximum size of the data object, it is atomic
If it is using SetObjectProtected (optiga_util_protected_update_start/continue/final)-> it is not atomic. but Version flag reflect unusable state until the completion of protected update