Re: Disabling and re-enabling extensions
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(Compliance hat on):
I'd like to dig into that a bit further. This has come up in the context of WARL registers, where changing the value of some CSR field1 causes some other CSR field2 value to become illegal, and therefore reading/applying that CSR field2 will then reflect a different, now legal value.
The question becomes: if CSR field1 is restored to its previous value (or some other value where the original CSR field2 was legal): does CSR field2 revert to that original value, or does it keep the newer (presumably legal) value?
Another way to look at this is: is it required that the illegal->legal mapping occur only when reading/using the CSR (by HW or SW), or that the result of an mapping force the field to be written (either explicitly on a write, or when changed while writing some other field)?
(Compliance hat going back into its closet)
On Wed, Sep 9, 2020 at 12:14 PM Paul Donahue <pdonahue@...> wrote: