ppt by mudit n vibhu
TRANSCRIPT
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Computer Operations1. Control Unit
2. Arithmetic and Logic Unit
3. Instruction Cycle
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Simple Computer
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Arithmetic
and
logic
unit
Control
unit
Memory
unit
Input/
output
unit
CPU
control bus
data bus
address bus
Simple Model Computer block diagramSimple Model Computer block diagram
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Arithmetic and logic unit
SR ACC
ALU
Arithmetic and Logical
operations are performed in
the ALU
1
ALU consists of an
accumulator (ACC), a set of
logic circuits, and a
status register (SR).
2
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Instruction
decoder PC
IR
Control unit
Control Unit
controls the overall
operations of the
computer.
1
Control Unit Consists
of the program
Counter (PC), the
instruction register (IR)
and the instructiondecoder.
2
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main memoryaddress decoder
MDR
MAR
Memory unit consists ofthe main store, the
memory data register
(MDR), the memory
address register (MAR),
and the address decoder.
1
Memory Unit 1
2Main store is composed of
a large number of memory
locations.
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Address decoder isresponsible for
selecting the
appropriate memory
location.
3
The memory data register holds
the piece of information read
from or written to the specified
memory location
4
The memory address registerholds the address of the
memory location to be
accessed.
5
Memory Unit 1
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Instruction Cycle
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Instruction Cycle
The instruction is fetched from memory
addressed by PC.
PC is advanced to address the next instruction.2
1
3 Instruction Decoder decodes theinstruction held in IR.
4 Instruction is then executed.
The process is repeated until the complete set
of instructions is fetched.
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Fetch instruction
from memory to IR
Increment PCExecute the
instruction
Decode the
instruction
Instruction Cycle
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main memory
SR
Instructiondecoder
addressdecoder
MDR
I/O unit
ACC
ALU
MAR
PC
IR
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main memory
SR
Instruction
decoder
address decoder
MDR
I/O unit
ACC
ALU
MAR
PC
IR
Memory unit
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main memory
SR
Instruction
decoder
address decoder
MDR
I/O unit
ACC
ALU
MAR
PC
IR
Memory unitControl unit
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Arithmetic and
logic unit main memory
SR
Instruction
decoder
address decoder
MDR
I/O unit
ACC
ALU
MAR
PC
IR
Memory unitControl unit
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Instruction
numberInstruction Address
location
1
2
3
10000
10001
10010Store the result held in the ACC
in memory location 11101
Load the contents in memorylocation 11111 into the ACC
Add the contents in memory
location 11110 to the ACC
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Main memory
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Load the contents in memory
location 11111 into the ACC
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Fetch cycle
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Fetch cycleFetch cycle- step 1
10000
PC
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PC
10000
Fetch cycleFetch cycle- step 2
MAR
10000
MAR
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10000
MAR
PC
Fetch cycleFetch cycle- step 3
Main memoryAddressdecoder
Instruction 1 10000
10000
Addressdecoder Main memory
10000
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10000
Main memoryFetch cycleFetch cycle
- step 4Addressdecoder
Instruction 1
Instruction 2
Instruction 3
10001
10010
11111
MDR
Instruction 1
Instruction 1 MDR
Number 1
10000
10000
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MDR
10000
10000
Fetch cycleFetch cycle- step 5
IRInstruction 1 IR Instruction 1Instruction 1
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Executing cycle
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Executing cycleExecuting cycle- step 1
1000010000PC
Instruction 1
PC10001
Instruction 1
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PCPC
Instruction 1Instruction 1
Executing cycleExecuting cycle- step 2
10000
Instruction
decoder
IR
10001
Instruction 1
10001
IR
Instruction
decoder
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Instruction
decoder
Instruction
decoder
Executing cycleExecuting cycle- step 3
10000
MAR
10001
Instruction 1Instruction 1
11111
MAR
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Instruction 1
1111111111
MAR
Main memoryAddressdecoderAddressdecoder Main memory
Executing cycleExecuting cycle- step 4
Instruction 1
10001
11111
Number 1
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Instruction 1 MDR
Executing cycleExecuting cycle- step 5
Instruction 1
10001
11111
Number 1Number 1
MDRNumber 1
Number 1 11111
Main memory
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Instruction 1 MDRACC
Executing cycleExecuting cycle- step 6
10001
11111
Number 1
Number 1 Number 1ACC
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Fetch Executing
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Add the contents in memory
location 11110 to the ACC
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PC10001
MDRMDR
MAR
Number 1
PCPC
Main memoryAddressdecoder
Instruction 2
10000
10001
10010
IR
Fetch cycleFetch cycle
Instruction 1
11111
Number 1
10001
Instruction 2
Addressdecoder Main memory
10001
Instruction 2Instruction 2
10001
IR
10001
10001
Main memory
10001
MAR
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Executing cycleExecuting cycle
100011000111110
10001PCPC
10010
Number 1 Instruction 2Instruction 2Instruction 2
PC
Instruction
decoder
IR
10010
IR
Instruction
decoder
MAR
Instruction
decoder
MAR
11110
Addressdecoder Main memory
Number 2
Instruction 2
Number 2
MDRNumber 2
Number 2
ACCNumber 1Number 1Result
11110
MAR
11110
Main memory
ALU
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Store the result held in the ACC
in memory location 11101
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10010PC
MDRMDR
MAR
Main memoryAddressdecoder
10000
IR
Fetch cycleFetch cycle
Instruction 1
11111
Number 1
10010
MARMAR
Addressdecoder Main memory
10010
Instruction 3Instruction 3
10010
IR
10010
Main memory
10010
Instruction 3Instruction 310010
Result
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Main memoryMain memory
Result
100011000111101
10001PCPC
10011
Instruction 2Instruction 3Instruction 3
PC
Instruction
decoder
IR
10011
IR
Instruction
decoder
MAR
Instruction
decoder
MAR
11101
Addressdecoder
Number 2
Instruction 3
Result
MDRResultACCResult
11101
MAR
1110111101
Main memoryExecuting cycleExecuting cycle
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Summary
Register Abbreviation unction
Instruction
RegisterIR
Stores the current
instruction
Program
CounterPC
Stores the address of
the next instruction
to be executed.
InstructionDecoder
---
Decode the
instruction in IR
Control nit
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The End !!!
Thank You!!!