Section 7.8
Review Questions

Hardware DFAs

  1. Referring to the following hardware DFA, write the next state number in the blank provided for each combination of current state and condition.
                 In state...     on condition...          go to state...
               
                      2               a                   _____________
               
                      2               c                   _____________
               
                      3               d                   _____________
               
                      0               a                   _____________
               
                      1               c                   _____________
               
                      1               b                   _____________
  1. If there were 20 different states, how many flip-flops would you need for the DFA state register?
  1. Show the AND gate that controls the S1 control wire. Which instructions set the S1 wire? (S1 is one of the inputs to the shifter.)
  1. Since the IR register is only changed at one point during the instruction cycle, what STATE wire would control IR-LD? (Refer to Fig. 7.7.2)
  1. Which instructions cause the DFA to move directly from state 2 to state 4, bypassing state 3 entirely? (Refer to Fig. 7.7.2)