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10.2 MODELS FOR SEQUENTIAL MACHINES 423

Next State (NS)
Functions

Present
State
Inputs—^ Memory —^Outputs
Outputs

(a)

(b)
Next State (NS)
Functions
( _
External
Inputs ^l Next State T Present
~ ' " State
(PS)
Outputs

(c)
FIGURE 10.3
Development of the basic model for sequential machines, (a) The memory section only, (b) Model
for an FSM capable of performing the sequence in Fig. 10.2a, showing the memory section and
NS-forming logic, (c) The basic model for an FSM capable of performing the sequence in Fig. 10.2b
when the external input is X.

External
Inputs • Next State Output
(IP) — * Forming Memory PS Forming
-* Logic Logic

PS Feedback

FIGURE 10.4
Moore's model for a sequential machine capable of performing the bidirectional binary sequence in
Fig. 10.2c, showing the basic model in Fig. 10.3c with the added output-forming logic that depends
only on the PS.