question1 animation: johnson ring counter ...questions question1 animation: johnson ring counter...
TRANSCRIPT
Questions
Question 1
Animation: Johnson ring counter
This question consists of a series of images (one per page) that form an animation. Flip the pages withyour fingers to view this animation (or click on the ”next” button on your viewer) frame-by-frame.
The following animation shows a 4-bit Johnson ring counter circuit. Watch what happens as the clock
signal oscillates. Here are some things to look for:
• Note when the logic state at each flip-flop input gets sent to the Q output.
• Why do you think this is called a ”ring” counter circuit?
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D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0 0
1
1 0 0 0
2
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0 0
1
1 0 0 0
3
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0 0
1
1 0 0 0
4
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0 0
1
1 0 0 01 1
5
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0
1
1 0 01 1
6
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0
1
1 0 01 1
7
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0
1
1 0 01 1
8
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0
1
1 0 01 1
9
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0
1
1 0 01 1 1 1
10
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0
1
1 01 1 1 1
11
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0
1
1 01 1 1 1
12
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0
1
1 01 1 1 1
13
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0
1
1 01 1 1 1
14
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0
1
1 01 1 1 1 1 1
15
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0
1
1 1 1 1 1 1 1
16
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0
1
1 1 1 1 1 1 1
17
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0
1
1 1 1 1 1 1 1
18
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0
1
1 1 1 1 1 1 1
19
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0
1
1 1 1 1 1 1 1 1
0
0
20
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1 1 1
0
0
21
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1 1 1
0
0
22
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1 1 1
0
0
23
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1 1 1
0
0
24
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1 1 1
0
0 0 0
25
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1
0
0 0 0
26
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1
0
0 0 0
27
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1
0
0 0 0
28
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1
0
0 0 0
29
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1 1 1
0
0 0 0 0 0
30
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1
0
0 0 0 0 0
31
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1
0
0 0 0 0 0
32
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1
0
0 0 0 0 0
33
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1
0
0 0 0 0 0
34
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1 1 1
0
0 0 0 0 0 0 0
35
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1
0
0 0 0 0 0 0 0
36
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1
0
0 0 0 0 0 0 0
37
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1
0
0 0 0 0 0 0 0
38
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1
0
0 0 0 0 0 0 0
39
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
1
0
0 0 0 0 0 0 0 0
1
1
40
D
C
Q
Q D
C
Q
Q D
C
Q
Q D
C
Q
Q
Clk
2 310
ClockVDD
Gnd
Q0
Q1
VDD
Gnd
VDD
Gnd
VDD
Gnd
VDD
Gnd
Q2
Q3
0 0 0 0 0 0 0
1
1
file 03234
41
Answers
Answer 1
Note that each rising edge of the clock pulse has its own frame in the animation sequence, to better
show you what happens at those crucial times.
42
Notes
Notes 1
The purpose of this animation is to let students study the behavior of this counter circuit and reach
their own conclusions. Similar to experimentation in the lab, except that here all the data collection is done
visually rather than through the use of test equipment, and the students are able to ”see” things that are
invisible in real life.
In this animation, I show each rising edge of the clock signal in its own frame, whereas the falling edge
of the clock shares a frame with the first half of the ”low” state. I do this because these are positive edge-
triggered flip-flops, and so the rising edge of the clock pulse is most important. I could have slowed things
down on the falling edge of the clock as well, but since there is little ”action” happening then, I decided to
save a frame and make it a shorter animation.
43