fetch-execute cycle fetch the next instruction decode execute it
TRANSCRIPT
Machine Code and the Fetch-Execute Cycle
Fetch-Execute Cycle
• Fetch the next instruction• Decode• Execute It
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
PC
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
PC
2000
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
1 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2000
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
1 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2002
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
1 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2002
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
1 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2002
MBR
100A
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
FETCH1
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2002
MBR
100A
CIR
Op-Code Operand
0001 0000 0000 1010
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
1 DECODE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2002
MBR
100A
CIR
Op-Code Operand
0001 0000 0000 1010
ACCALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
DECODE
Instruction Decoded
1
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2002
MBR
100A
CIR
Op-Code Operand
0001 0000 0000 1010
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE1
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2002
PC
2002
MBR
CIR
Op-Code Operand
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
2 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2002
PC
2004
MBR
CIR
Op-Code Operand
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
2 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2002
PC
2004
MBR
CIR
Op-Code Operand
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
2 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2002
PC
2004
MBR
8019
CIR
Op-Code Operand
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
FETCH2
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2002
PC
2004
MBR
8019
CIR
Op-Code Operand
1000 0000 0001 1001
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
2 DECODE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
2000
PC
2004
MBR
8019
CIR
Op-Code Operand
1000 0000 0001 1001
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
DECODE
Instruction Decoded
2
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 00
001A 00
001B 00
001C 00
MAR
0019
PC
2004
MBR
0A
CIR
Op-Code Operand
1000 0000 0001 1001
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE2
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
0019
PC
2004
MBR
0A
CIR
Op-Code Operand
1000 0000 0001 1001
ACC
0AALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
2 EXECUTE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2004
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
3 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2006
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
3 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2006
MBR
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
3 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2006
MBR
1005
CIR
Op-Code Operand
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
FETCH3
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2006
MBR
1005
CIR
Op-Code Operand
0001 0000 0000 0101
ACC
ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
3 DECODE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2006
MBR
1005
CIR
Op-Code Operand
0001 0000 0000 0101
ACCALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
DECODE
Instruction Decoded
3
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2004
PC
2006
MBR
1005
CIR
Op-Code Operand
0001 0000 0000 0101
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE3
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2006
PC
2006
MBR
CIR
Op-Code Operand
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
4 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2006
PC
2008
MBR
CIR
Op-Code Operand
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
4 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2006
PC
2008
MBR
CIR
Op-Code Operand
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
4 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2006
PC
2008
MBR
4019
CIR
Op-Code Operand
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
FETCH4
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2006
PC
2008
MBR
4019
CIR
Op-Code Operand
0100 0000 0001 1001
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
4 DECODE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2006
PC
2008
MBR
4019
CIR
Op-Code Operand
0100 0000 0001 1001
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
DECODE
Instruction Decoded
4
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
019
PC
2008
MBRCIR
Op-Code Operand
0100 0000 0001 1001
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE4
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
019
PC
2008
MBRCIR
Op-Code Operand
0100 0000 0001 1001
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE4
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
019
PC
2008
MBR
0A
CIR
Op-Code Operand
0100 0000 0001 1001
ACC
05ALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE4
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
019
PC
2008
MBR
0A
CIR
Op-Code Operand
0100 0000 0001 1001
ACCALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE4
0A + 05 = 0F
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
019
PC
2008
MBR
0A
CIR
Op-Code Operand
0100 0000 0001 1001
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
EXECUTE4
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2008
PC
2008
MBR
CIR
Op-Code Operand
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
5 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2008
PC
2010
MBR
CIR
Op-Code Operand
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
5 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2008
PC
2010
MBR
CIR
Op-Code Operand
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
5 FETCH
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2008
PC
2010
MBR
801A
CIR
Op-Code Operand
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
FETCH5
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2008
PC
2010
MBR
801A
CIR
Op-Code Operand
1000 0000 0001 1100
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
5 DECODE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
2008
PC
2010
MBR
801A
CIR
Op-Code Operand
1000 0000 0001 1100
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
DECODE
Instruction Decoded
5
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 00
001B 00
001C 00
MAR
001A
PC
2010
MBR
0F
CIR
Op-Code Operand
1000 0000 0001 1100
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
5 EXECUTE
Instruction Memory
2000 100A (LOAD #10)
2002 8019 (STORE 25)
2004 1005 (LOAD #05)
2006 4019 (ADD 25)
2008 801A (STORE 26)
Data Memory
0018 00
0019 0A
001A 0F
001B 00
001C 00
MAR
001A
PC
2010
MBR
0F
CIR
Op-Code Operand
1000 0000 0001 1100
ACC
0FALU
PC Program Counter
MAR Memory Address Register
MBR Memory Buffer Register
CIR Current Instruction Register
ALU Arithmetic and Logic Unit
ACC Accumulator
5 EXECUTE