The document shows the step-by-step operations of an arithmetic logic unit (ALU) performing an addition of registers R1 and R2. It loads the operands into the registers from memory, selects the operands for the addition, performs the addition, and stores the result in the register Z.
1. Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R2
Z
1
2. Pcout, MARin, Read, Select4, Add, Zin
Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R1
2
Z
2
3. Pcout, MARin, Read, Select4, Add, Zin
Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R1
2
Z
3
4. Pcout, MARin, Read, Select4, Add, Zin
Control/Decode
PC Unite
Read
MAR IR
MDR
Constant 4 Y
R1
R1
2
Z
4
5. Pcout, MARin, Read, Select4, Add, Zin
Control/Decode
PC Unite
Read
MAR IR
MDR
Constant 4 Y
R1
Select4
R1
2
Z
5
6. Pcout, MARin, Read, Select4, Add, Zin
Control/Decode
PC Unite
Read
MAR IR
MDR
Constant 4 Y
R1
Select4
R1
ADD 2
PC+4
Z
6
7. Pcout, MARin, Read, Select4, Add, Zin
Control/Decode
PC Unite
Read
MAR IR
MDR
Constant 4 Y
R1
Select4
R1
2
ADD
PC+4
Z
7
8. Zout, Pcin, Yin, WMFC
Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R2
R1
2
Z
8
9. Zout, Pcin, Yin, WMFC
Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R1
2
Z
9
10. Zout, Pcin, Yin, WMFC
Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R2
1
Z
10
11. Zout, Pcin, Yin, WMFC
Control/Decode
PC Unite
MAR IR
WMFC
MDR
Constant 4 Y Waiting for the Data to
come from the memory.
R1 When the data or
Instruction is available, it
will be Latched into MDR
R1
2
Z
11
12. MDRout, IRin
Control/Decode
PC Unite
MAR IR
MDR
Constant 4 Y
R1
R2
1
Z
12
13. MDRout, IRin
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4 Y
R1
R2
Z
13
14. R1out, Yin, SELECTY
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4 Y
R1
R2
Z
14
15. R1out, Yin, SELECTY
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
R2
Z
15
16. R1out, Yin, SELECTY
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
Z
16
17. R2out, ADD, Zin
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
Z
17
18. R2out, ADD, Zin
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
ADD
Z
18
19. R2out, ADD, Zin
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
ADD
Z
19
20. Zout, R1in, END
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
ADD
Z
20
21. Zout, R1in, END
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
ADD
Z
21
22. Zout, R1in, END
Control/Decode
PC Unite
MAR IR
MDR ADD R1, R2
Constant 4
Y
R1
SelectY
R2
ADD
Z
22