Hi, Andy, Peter,

At the HC08 core "SWI has the highest priority other than reset; once
the SWI opcode is fetched, no other interrupt can be honored until the
SWI vector has been fetched." This instruction is not maskable by
setting the I - interrupt mask bit.
Also, this instruction is loaded to instruction register automatically
when the Break Module is activated (when PC equal to predefined address,
or software activate it).

These features might be useful in some cases on that architecture.

Best regards,
Oleg