the fetch-execute cycle
DESCRIPTION
THE FETCH-EXECUTE CYCLE. REGISTERS. ACC. Check for interrupts. Fetch instruction from memory. MDR. MAR. 1. CIR. Execute instruction. Update Program counter. PC. 1. MEMORY Location Contents. THE PROGRAM. The address of the first instruction is copied from the PC to the MAR. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/1.jpg)
THE
FETCH-EXECUTE
CYCLE
![Page 2: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/2.jpg)
1
1
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The address of the first
instruction is copied from the PC to the MAR
![Page 3: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/3.jpg)
LDA 23
1
1
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The first instruction is read into the
MDR
![Page 4: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/4.jpg)
LDA 23
LDA 23
1
1
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The first instruction is
copied into the CIR
![Page 5: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/5.jpg)
LDA 23
LDA 23
1
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The program counter is
updated to point to the next instruction
![Page 6: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/6.jpg)
LDA 23
LDA 23
23
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The address part of the current instruction is placed in the
MAR
![Page 7: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/7.jpg)
14
LDA 23
23
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The contents of the location
whose address is in the MAR are loaded into the
MDR
![Page 8: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/8.jpg)
14
14
LDA 23
23
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The contents of the MDR are
copied into the ACC
![Page 9: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/9.jpg)
14
14
LDA 23
23
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The Status Register is checked for interrupts
![Page 10: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/10.jpg)
14
14
LDA 23
2
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The address of the second
instruction is copied from the PC to the MAR
![Page 11: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/11.jpg)
14
ADD 72
LDA 23
2
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The second instruction is read into the
MDR
![Page 12: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/12.jpg)
14
ADD 72
ADD 72
2
2
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The second instruction is
copied into the CIR
![Page 13: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/13.jpg)
14
ADD 72
ADD 72
2
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The program counter is
updated to point to the next instruction
![Page 14: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/14.jpg)
14
ADD 72
ADD 72
72
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The address part of the current instruction is placed in the
MAR
![Page 15: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/15.jpg)
14
35
ADD 72
72
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The contents of the location
whose address is in the MAR are loaded into the
MDR
![Page 16: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/16.jpg)
49
35
ADD 72
72
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The contents of the MDR are added to the
ACC
![Page 17: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/17.jpg)
49
35
ADD 72
72
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The Status Register is checked for interrupts
![Page 18: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/18.jpg)
49
35
ADD 72
3
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The address of the third
instruction is copied from the PC to the MAR
![Page 19: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/19.jpg)
49
STA 53
ADD 72
3
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The third instruction is read into the
MDR
![Page 20: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/20.jpg)
49
STA 53
STA 53
3
3
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The third instruction is
copied into the CIR
![Page 21: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/21.jpg)
49
STA 53
STA 53
3
4
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The program counter is
updated to point to the next instruction
![Page 22: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/22.jpg)
49
STA 53
STA 53
53
4
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The address part of the current instruction is placed in the
MAR
![Page 23: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/23.jpg)
49
49
STA 53
53
4
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 26
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The contents of the ACC are
copied into the MDR
![Page 24: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/24.jpg)
49
49
STA 53
53
4
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 49
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The contents of the MDR are
copied into the memory location whose address is in the MAR
![Page 25: THE FETCH-EXECUTE CYCLE](https://reader031.vdocument.in/reader031/viewer/2022012404/56812b26550346895d8f2982/html5/thumbnails/25.jpg)
49
49
STA 53
53
4
REGISTERS
ACC
MDR
MAR
CIR
PC
1 LDA 23
2 ADD 72
3 STA 53
THE PROGRAM
23 14
53 49
72 35
MEMORY
Location Contents
Fetch instruction from memory
Update Program counter
Execute instruction
Check for interrupts
The Status Register is checked for interrupts