Improve misa clarification

riscv · Feb 10, 2024 · 29ef7de · 29ef7de
1 parent 1233bcf
commit 29ef7de
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/src/machine.adoc b/src/machine.adoc
@@ -231,7 +231,9 @@ all state uniquely associated with that extension is UNSPECIFIED, unless otherwi
 NOTE: Although one of the bits 25--0 in `misa` being set to 1 implies that
 the corresponding feature is implemented, the inverse is not necessarily
 true: one of these bits being clear does not necessarily imply that the
-corresponding feature is absent.
+corresponding feature is not implemented.  This follows from the fact that,
+when a feature is not implemented, the corresponding opcodes and CSRs become
+reserved, not necessarily illegal.
 
 ==== Machine Vendor ID Register `mvendorid`