Dear Michael Karas
You wrote:-
"if there was any particular advantage in terms of run time performance of ending the code sequence with the XCH instruction over the MOV instruction"
That's interesting! Can I have example when code sequence for arith/logic can affect performance?.When you posed the puzzler#1 you wanted "best way".Although "best" is value judgement,in µC domain we want shortest code doing the job.And your puzzler was good in the sense that the answer were known - task was to do it in shortest possible steps.Now when I achieve that as proved by my explanation what is point checking for better code sequence?Please help me learn.
A.S.Rudra