Date post: | 30-Dec-2015 |
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1
1
REGISTERS
ACC
MBR
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
LDA 23
1
1
REGISTERS
ACC
MBR
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
MBR
LDA 23
LDA 23
1
1
REGISTERS
ACC
MBR
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
LDA 23
LDA 23
1
2
REGISTERS
ACC
MBR
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
LDA 23
LDA 23
23
2
REGISTERS
ACC
MBR
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
14
LDA 23
23
2
REGISTERS
ACC
MBR
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
MBR
14
14
LDA 23
23
2
REGISTERS
ACC
MBR
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 MBR are
copied into the ACC
14
14
LDA 23
23
2
REGISTERS
ACC
MBR
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
14
14
LDA 23
2
2
REGISTERS
ACC
MBR
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
14
ADD 72
LDA 23
2
2
REGISTERS
ACC
MBR
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
MBR
14
ADD 72
ADD 72
2
2
REGISTERS
ACC
MBR
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
14
ADD 72
ADD 72
2
3
REGISTERS
ACC
MBR
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
14
ADD 72
ADD 72
72
3
REGISTERS
ACC
MBR
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
14
35
ADD 72
72
3
REGISTERS
ACC
MBR
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
MBR
49
35
ADD 72
72
3
REGISTERS
ACC
MBR
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 MBR are added to the
ACC
49
35
ADD 72
72
3
REGISTERS
ACC
MBR
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
49
35
ADD 72
3
3
REGISTERS
ACC
MBR
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
49
STA 53
ADD 72
3
3
REGISTERS
ACC
MBR
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
MBR
49
STA 53
STA 53
3
3
REGISTERS
ACC
MBR
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
49
STA 53
STA 53
3
4
REGISTERS
ACC
MBR
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
49
STA 53
STA 53
53
4
REGISTERS
ACC
MBR
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
49
49
STA 53
53
4
REGISTERS
ACC
MBR
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 MBR
49
49
STA 53
53
4
REGISTERS
ACC
MBR
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 MBR are
copied into the memory location whose address is in the MAR