Hello Ronnie
1. Can I just read and write to the OCOTP shadow registers (0x401F4400 - 0x401F46F0) at will, and the efuses will NOT be changed?
All fuse words in efusebox are shadowed. Therefore, fuse information is available through memory-mapped shadow registers. If fuses are subsequently programmed, the shadow registers should be reloaded to keep them coherent with the fuse bank arrays. So, writing to the shadow registers will not change the fuses.
Shadow register bits can be overridden by software until the corresponding fuse lock bit for the region is set. When the lock shadow bit is set, the shadow registers for that lock region become write-locked.
2. Are the contents of these shadow registers lost at reset because they are reloaded with the actual efuse values?
Yes, this is correct.
3. If so, does that mean the SRK efuses have to be burned so that signed/encrypted boot works?
To do a High-Assurance Boot you need to burn the SRK fuses, this cannot be done only with the shadow registers.
Have a great day,
Victor
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