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chipsalliance / caliptra-sw

Caliptra software (ROM, FMC, runtime firmware), and libraries/tools needed to build and test
Apache License 2.0
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Field Entropy potential inconsistency #1565

Open A-Rovelli opened 3 weeks ago

A-Rovelli commented 3 weeks ago

Hello,

We have noticed some differences, or potential inconsistencies, between the fuse map and the corresponding registers, we would need clarification on this. We refer respectively to the tables on the following pages.

Fuse map: https://github.com/chipsalliance/Caliptra/blob/main/doc/Caliptra.md#fuse-map Fuse and architectural registers https://github.com/chipsalliance/caliptra-sw/blob/main/rom/dev/README.md#fuse-and-architectural-registers

The first issue is about the size of the field entropy: map: FIELD ENTROPY (obfuscated) 256 bits reg: FUSE_FIELD_ENTROPY 384 bits

Thanks in advance.

jhand2 commented 2 weeks ago

I believe the main spec is correct (256 bits). That also aligns with https://chipsalliance.github.io/caliptra-rtl/main/external-regs/?p=caliptra_top_reg.generic_and_fuse_reg.fuse_field_entropy%5B0%5D. @mhatrevi to confirm.

jhand2 commented 2 weeks ago

Ah, I see Caleb already confirmed in https://github.com/chipsalliance/Caliptra/issues/192. Thanks, we'll make this update in the ROM spec.