5. BASIC DEFINITIONS OF
SEQUENTIAL CIRCUITS
Sequential circuit
Any digital circuit with memory due to
feedback, particularly a circuit with latches or
flip-flops is a sequential circuit
5
6. Moore Circuits
In a Moore circuit, the outputs are function of the
present state only, i.e.; function of flip-flops
outputs
6
7. Mealy Circuits
In a Mealy circuit, the output is a function of both
the present state and the external inputs
7
8.
Counters
A counter is a sequential circuit that goes
through a prespecified sequence of states upon
the application of input pulses
8
9. State Diagram
The sequence of states of a sequential circuit,
along with the external input and the output of
the circuit, can be represented graphically using a
state diagram
9
10. B
ANALYSIS OF A SEQUENTIAL
CIRCUIT
get the flip-flops input functions:
RA =B’ x , SA = BX’ , RB = AX’ , SB = A’ x
, also get the output function(s) :
Y = A’ x
10
12. ANALYSIS OF A SEQUENTIAL
CIRCUIT
RA =B’ x , SA = BX’ , RB = AX’ , SB = A’ x ,
Y=A’x
Make the state table of the circuit as follows
:
12
13. ANALYSIS OF A SEQUENTIAL
CIRCUIT
Draw the state diagram for the circuit
13
14. Analysis of synchronous counters
Starting at QC QB QA = 000, what sequence does
the synchronous circuit of three D flip-flops
shown in figure(53) step through ?
14
24. Design with unused states
Design a sequential circuit to satisfy the state
diagram shown in figure(57). Use SR flip-flops.
Treat the unused states as do not care
conditions.
24
29. Effect Of The Unused States
Analyze the sequential circuit obtained and
determine the effect of the unused states
The unused states are : 000 , 110 , 111. We can
solve this problem like any analysis problem
Flip-flops input functions
29