Additional Types of Shift Registers:
Parallel in/Parallel out
Parallel in/Serial out
Serial in/Parallel out
Serial in/Serial out
Additional Types of Counters:
Ring Counters; a 1 is shifted through each flip-flop while all the other flip-flop outputs are 0.
(one hot encoding is a recommended design)
Twisted Ring Counters (or switch tail ring counter, Johnson counter, mobius counter)
Linear Feedback Shift Register Counter (or maximum length shift counters)
Depending on design it will count all possible states, but skips all 0s and 1s states.
Recommendation: Reader is encouraged to explore full definition of these counters and others
through independent research.
Adding an Enable Input
It may be necessary to stop the count at times and then continue counting. In this section we will
design a “Full-Encoded Stoppable Counter”. This counter will count up as long as EN is asserted;
otherwise it will stop the counting.
GND
Vcc=+5V
Diode
Schmitt
Trigger
Vc CLR CLR’
C=10 uF
R=10 K Ω
On
Vcc
Off
5V
Vc
0V
H
CLR
L
H
CLR’
L
RC with C grounded
GND
Vcc=+5V
Vc CLR’ CLR
C=10 uF
On
Vcc
Off
5V
Vc
0V
H
CLR’
L
H
CLR
L
RC with R grounded
R=10 K Ω
Power is off Power is on
Time it takes the Vc = 5(1- e –^ t/RC )^
to trigger the Schmitt trigger
Time it takes the Vc = 5 (e –^ t/RC^ ) to
trigger the Schmitt trigger