#avr Logs

Jul 04 2022

03:39 AM exp: the xmega NVR application notes state that to use the CRC module on flash, boot lock bits must be unset
03:48 AM exp: that's a pretty bizarre requirement isn't it? i would rather lock my bootloader so it may only be read
03:48 AM exp: has anyone some experience using this?
04:14 AM Cracki: no experience with xmegas but on the regular megas, iirc, there were lock bits to prohibit writing, but also to prohibit READING
04:14 AM Cracki: reading from user code, that is
04:14 AM Cracki: it would execute fine but you can't read it
04:15 AM Cracki: and it would make sense for CRC to not work if that type of locking is active
04:15 AM Cracki: if it requires writability, that would confuse me too
04:19 AM specing_ is now known as specing
04:23 AM exp: Cracki: yeah that's what confuses me, i can leave reading unlocked, but it's very explicit saying "must be unprogrammed (no locks)"
04:24 AM Cracki: maybe the technical writer had a brainfart... does it fail with write lock bit?
04:24 AM exp: that's the next stage of testing, something is failing currently
04:24 AM Cracki: does crc involve the operation writing its result to somewhere in flash?
04:24 AM exp: but i don't have a cause
04:25 AM exp: in this case i just need to check the final value, but i'm going to have to rewrite the code i guess
04:25 AM exp: my fault for jumping too far ahead
04:27 AM Cracki: random google result talks about NVM_CMD_BOOT_CRC_gc vs NVM_CMD_APP_CRC_gc
04:28 AM exp: in this case i'm trying to CRC a small section of app flash, boot flash gets verified by programmer
04:28 AM exp: wouldn't hurt to do both
04:29 AM Cracki: I'd peek in the errata sheet. maybe they confessed to the deed already.
04:29 AM Cracki: would be a strange silicon bug, if it actually required writable flash
04:20 PM specing_ is now known as specing