In addition to the above, it is necessary to select whether, in `svstep`
mode, the Vector CR Field is to be overwritten or not: in some cases
it is useful to know but in others all that is needed is the branch itself.
-In the case of `sv.bc` there is no additional bitspace so the ``AA`
+In the case of `sv.bc` there is no additional bitspace, so on the
+basis that it is rarely used, the `AA`
field is re-interpreted instead to be `Rc`. For `sv.bclr`, there is free
bitspace and so bit 16 has been chosen as `Rc`.