Hardware Reference
In-Depth Information
Exercise 3.3: By-Hand Design of a Moore Machine #2
Consider the Moore machine of i gure 5.7c, which implements a short-pulse
generator.
a) Design it “by hand” using sequential encoding. Show that
y
=
q
0
.
b) Design it using Gray encoding. Show that
y
=
q
1
·
q
0
.
c) Design it using the following user-dei ned encoding: A = “
′
−
0”, B = “01”, C = “11”.
·
q
0
.
d) Draw all three circuits and show that the last one is the simplest.
e) Which of these circuits is/are guaranteed to have a glitch-free output, with better
time predictability? Explain.
Show that
d
0
=
x
,
d
1
=
q
0
, and
y
=
q
1
′
Exercise 3.4: By-Hand Design of a Mealy Machine
a) Draw a Mealy-type state transition diagram for the parity detector of i gure 5.5.
b) Design a circuit that implements this machine, with sequential encoding.
Exercise 3.5: Time Behavior of a Moore Machine
Say that the parity detector of i gure 5.4b operates with the clock signal of i gure 3.26,
receiving at the input the signal
x
also included in the i gure. Draw the other two
waveforms (machine's present state and output; the initial part of
pr_state
was already
i lled). Does the output change only when the state changes?
Exercise 3.6: Time Behavior of a Mealy Machine
This exercise is a continuation of the one above.
a) Draw a Mealy-type solution for the parity detector of i gure 5.4.
b) Say that this machine is operating with the clock of i gure 3.27, receiving the signal
x
also included in the i gure. Draw the other two waveforms (machine's present state
and output). Does the output change only when the state changes?
c) Compare the time behavior of this Mealy solution against that of the Moore coun-
terpart developed in the previous exercise. Which is different (
pr_state
or
y
or both)
from one solution to the other?
Figure 3.26
