Hardware Reference
In-Depth Information
the notation is changed from Moore to Mealy style, as shown in i gure 1.10b, and
then the merging is done in i gure 1.10c.
Another example is presented in
i gures 1.10d-f following the same procedure. The
analysis of this example is left to the reader. The reader is also invited to apply this
procedure to the Moore machine of i gure 1.3b and see if the Mealy machine of i gure
1.3c results.
As expected, because of the highly restricting requirements for state merging
(described above), in practical engineering problems the number of additional states
in a Moore machine compared to its Mealy counterpart is generally very small.
1.8 Mealy-to-Moore Conversion
Mealy machines, too, can be converted into corresponding Moore machines. As seen
above, the former can be smaller than the latter, although the difference (in number
of states) in useful engineering applications is generally negligible.
The conversion principle consists again of two steps, illustrated in
i gures 1.11a-c.
A Mealy FSM with three states is presented in i gure 1.11a. The i rst step, shown in
i gure 1.11b, consists of changing the notation from Mealy to Moore style. Because in
a Mealy machine the same state can exhibit more than one output value, the resulting
Moore diagram might have states with
conditional
outputs, such as state A in the i gure.
The next step is to split each state into as many states as the possible output values.
Figure 1.11
Mealy-to-Moore conversion principle. (a) Original Mealy machine. (b) Mealy-to-Moore notation
change. (c) Splitting of state A into A
′
and A
″
. (d-f) Another example, following the same procedure.
