22C: 060 Computer Organization
Assignment 3
Sample Solution
Chapter 3, Problem 37
Here is the trace. Call the four Q’s (from left to right) Q4 Q3 Q2 Q1:
Q4 Q3 Q2 Q1
1
2
3
4
5
6
7
8
9
0 0 0 0
1 0 0 0
1 1 0 0
1 1 1 0
1 1 1 1
0 1 1 1
0 0 1 1
0 0 0 1
0 0 0 0
It is called a twisted ring counter or a Johnson counter. This circuit can count up and down (up to 4).
Chapter 3, Problem 40
The question is awkward, since it forces an value into the Z-input, making the connection from Q to Z a
meaningless one. Also, the –O—on the carry output C confuses readers about whether an inversion in
implied there (apparently not). I have given points regardless of how you interpreted it.
X Y Z
S Q
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
0 0
1 0
1 0
0 1
1 0
0 1
0 1
1 1
Chapter 4, Problem 13
Label
Hex address
Instruction
Binary
Hex
100
Load A
0001 0001 0000 1000
1108
101
Add One
0011 0001 0000 1001
3109
102
Jump S1
1001 0001 0000 0110
9106
S2
103
Add One
0011 0001 0000 1001
3109
104
Store A
0010 0001 0000 1000
2108
105
Halt
0111 0000 0000 0000
7000
S1
106
Add A
0011 0001 0000 1000
3108
107
Jump S2
1001 0001 0000 0011
9103
A
108
HEX 0023
0000 0000 0010 0011
0023
One
109
HEX 0001
0000 0000 0000 0001
0001
