The block diagram shown at right consists of

three blocks of logic:

$$ a $8-$to$-3$ priority encoder, where x$7$ has the

highest priority and x $0$ the lowest priority

$$ a $3-$bit unsigned subtractor, A $$ B$,$ with the

A operand tied off to $1112.$

$$ a barrel shifter that can shift any number of

positions to the left specified by S $2$S$1$ S$0$