1. COMPUTER ORGANIZATION AND ARCHITECTURE
15EM2001
COMPUTER ORGANIZATION AND ARCHITECTURE
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2. Introduction to computer System and its sub modules
There are two basic types of electrical signals, namely, analog and digital. The analog signals are continuous in nature and digital signals are discrete in nature.
The electronic device that works with continuous signals is known as analog device and the electronic device that works with discrete signals is known as digital device.
We use ‘0’ to represent LOW and ‘1’ to represent HIGH.
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3. Computer Architecture
Computer architecture refers to those parameters of a computer system that are visible to a programmer or those parameters that have a direct impact on the logical execution of a program.
Examples of architectural attributes include the instruction set, the number of bits used to represent different data types, I/O mechanisms, and techniques for addressing memory.
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4. Computer Organization
Computer organization refers to the operational units and their interconnections that realize the architectural specifications.
Examples of organizational attributes include those hardware details transparent to the programmer, such as control signals, interfaces between the computer and peripherals, and the memory technology used.
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5. Basic Computer Model and different units of Computer
Central Processor Unit,
Input Unit,
Output Unit,
Memory Unit
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6. Number System & Representation
Decimal Number System (0-9)
Octal Number System (0-7)
Hexa-Decimal Number System (0-F)
Binary Number System (0, 1)
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7. Representation of Real Number
Binary representation of is
Therefore any real number can be converted to binary number system
There are two schemes to represent real number :
Fixed-point representation
2) Floating-point representation
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8. Fixed-point representation
Binary representation of is
To store this number, we have to store two information,
-- the part before decimal point and
-- the part after decimal point.
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9. Floating-point representation
In this representation, numbers are represented by a mantissa comprising the significant digits and an exponent part of Radix R. The format is:
Numbers are often normalized, such that the decimal point is placed to the right of the first non zero digit.
For example, the decimal number,
To store this number in floating point representation, we store 5236 in mantissa part and 3 in exponent part.
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10. Signed Integer Range of natural numbers is 0 to 2n-1
By including negative numbers -2n-1-1 to 2n-1-1
If we consider 8-bit number, then range of natural number is from
For signed integer range is from -127 to 127
Signed Magnitude Form
If MSB = 0 then it is +ve and if MSB = 1 then it is –ve
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11. Representation of Signed Integer in 1’s complement form
By adding ‘1’ to the result, it is ‘0’
Representation of Signed Integer in 2’s complement form
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12. Arithmetic & Logical Unit
Consider an ALU which can perform four arithmetic operations and four logical operations To distinguish between arithmetic and logical operation, we may use a signal line,
0 - in that signal, represents an arithmetic operation and
1 - in that signal, represents a logical operation.
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14. 4- bit Full Adder
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15. Binary Subtractor:
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16. Design of ALU
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18. Memory Unit RAM ROM Block Diagram of ROM Block Diagram of RAM
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19. Control Unit
To execute an instruction, the control unit of the CPU must generate the required control signal in the proper sequence.
To generate the control signal in proper sequence, a wide variety of techniques exist. Most of these techniques, however, fall into one of the two categories,
Hardwired Control
Microprogrammed Control
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20. Hardwired Control : In this hardwired control techniques, the control signals are generated by means of hardwired circuit. The main objective of control unit is to generate the control signal in proper sequence.
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21. Eg: Programmable Logic Array
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22. Microprogrammed Control
In microprogrammed control unit, the logic of the control unit is specified by a microprogram.
sequencing through microinstructions
generating control signals to execute each microinstruction.
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23. Control Word (CW) :
Control word is defined as a word whose individual bits represent the various control signal.
The individual control words in this microprogram are referred to as microinstructions.
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24. Machine Language
A processor can understand and execute machine instructions. Such instructions are simply binary numbers stored in the computer.
If a programmer wished to program directly in machine language, then it would be necessary to enter the program as binary data.
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25. Assembly Language
Assembly language is a programming language that is one step away from machine language.
Typically, each assembly language instruction is translated into one machine instruction by the assembler.
Assembly language is hardware dependent, with a different assembly language for each type of processor
I1: Move R3, R7 /R3 ← (R7)
I2: Load R8, (R3) /R8 ← Memory (R3)
I3: Add R3, R3, 4 /R3 ← (R3) + 4
I4: Load R9, (R3) /R9 ← Memory (R3)
I5: BLE R8, R9, L3 /Branch if (R9) > (R8)
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26. Load the contents of location 201 into the AC.
N = I + J + K
Load the contents of location 201 into the AC.
2. Add the contents of location 202 to the AC.
3. Add the contents of location 203 to the AC.
4. Store the contents of the AC in location 204.
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27. Assembly Language Compiler Interpreter Linker Loader
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28. Addressing Modes The most common addressing techniques are: Immediate
Direct
Indirect
Register
Register Indirect
Displacement
Stack
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29. To explain the addressing modes, the following notationis used:
A = contents of an address field in the instruction that refers to a memory
R = contents of an address field in the instruction that refers to a register
EA = actual (effective) address of the location containing the referenced operand
(X) = contents of location X
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30. Immediate Addressing Instruction Operand
The simplest form of addressing is immediate addressing
OPERAND = A
Immediate Addressing
Instruction
Opcode
Operand
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31. Direct Addressing Address field contains address of operand
Effective address (EA) = address field (A)
e.g. ADD A
Add contents of cell A to accumulator
Look in memory at address A for operand
Single memory reference to access data
No additional calculations to work out effective address
Limited address space
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32. Direct Addressing Diagram
Instruction
Address A
Memory
Operand
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33. Indirect Addressing
Memory cell pointed to by address field contains the address of (pointer to) the operand
EA = (A)
Look in A, find address (A) and look there for operand
e.g. ADD (A)
Add contents of cell pointed to by contents of A to accumulator
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34. Indirect Addressing Diagram
Instruction
Address A
Memory
Pointer to operand
Operand
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35. Register Addressing Operand is held in register named in address filed
EA = R
Limited number of registers
Very small address field needed
Shorter instructions
Faster instruction fetch
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36. Register Addressing No memory access Very fast execution
Very limited address space
Multiple registers helps performance
Requires good assembly programming or compiler writing
Direct addressing
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37. Register Addressing Diagram
Instruction
Register Address R
Registers
Operand
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38. Register Indirect Addressing
EA = (R)
Operand is in memory cell pointed to by contents of register R
Large address space (2n)
One fewer memory access than indirect addressing
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39. Register Indirect Addressing
Instruction
Opcode
Register Address R
Memory
Registers
Pointer to Operand
Operand
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40. Displacement Addressing
EA = A + (R)
Address field hold two values
A = base value
R = register that holds displacement
or vice versa
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41. Displacement Addressing Diagram
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42. Displacement Addressing
Relative Addressing
Base-Register Addressing
Indexing
auto-indexing
auto-incrementing
EA = A + (R)
R = (R) + 1
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43. Displacement Addressing
auto-decrementing
EA = A + (R)
R = (R) – 1
If indexing is performed after the indirection, it is termed postindexing
EA = (A) + (R)
With preindexing, the indexing is performed before the indirection:
EA = ( A + (R) )
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44. Stack Addressing Operand is (implicitly) on top of stack e.g.
ADD Pop top two items from stack and add
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45. Instruction Set
The operation of a CPU is determine by the instruction it executes, referred to as machine instructions or computer instructions. The collection of different instructions is referred as the instruction set of the CPU.
Each instruction must contain the information required by the CPU for execution.
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46. Opcodes are represented by abbreviations, called mnemonics, that indicate the operations
4-bits
6-bits
6-bits
Opcode
Operand1
Operand2
A simple instruction format
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47. The instruction set of a CPU can be categorized as follows:
1. Data Processing
2. Data Storage
3. Data Movement
4. Control
Types of Operands
Addresses
Numbers
Characters
Logical Data
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48. Types of Operations Data Transfer Arithmetic Logical Conversion
Input Output [ I/O ]
System Control
Transfer Control
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49. Data Transfer
Move (Transfer) Transfer word or block from source to destination
Store Transfer word from processor to memory
Load (fetch) Transfer word from memory to processor
Exchange Swap contents of source and destination
Clear (reset) Transfer word of 0s to destination
Set Transfer word of 1s to destination
Push Transfer word from source to top of stack
Pop Transfer word from top of stack to destination
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50. B. Arithmetic Add --------------Compute sum of two operands
Subtract Compute difference of two operands
Multiply Compute product of two operands
Divide Compute quotient of two operands
Absolute Replace operand by its absolute value
Negate Change sign of operand
Increment Add 1 to operand
Decrement -----Subtract 1 from operand
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51. C. Logical
AND Performs the logical operation AND bitwise
OR Performs the logical operation OR bitwise
NOT Performs the logical operation NOT bitwise
Exclusive OR Performs the specified logical operation Exclusive-OR bitwise
Test Test specified condition; set flag(s) based on outcome
Compare Make logical or arithmetic comparison Set flag(s) based on outcome
Set Control Variables------Class of instructions to set controls for protection purposes, interrupt handling, timer control etc.
Shift Left (right) shift operand, introducing constant at end
Rotate Left (right) shift operation, with wraparound end
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52. D. Input/output
Input (Read)----- Transfer data from specified I/O port or device to destination (e.g., main memory or processor register)
Output (Write)----Transfer data from specified source to I/O port or device.
Start I/O Transfer instructions to I/O processor to initiate I/O operation.
Test I/O Transfer status information from I/O system to specified destination
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53. E. System Control
System control instructions are those which are used for system setting and it can be used only in privileged state.
Typically, these instructions are reserved for the use of operating systems.
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54. F. Transfer of Control
The most common transfer-of-control operations found in instruction set are:
Branch
Skip
Procedure call.
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55. BRP X ----Branch to location X if result is positive
BRN X ---- Branch to location X if result is negative
BRZ X----- Branch to location X is result is zero
BRO X----- Branch to location X if overflow occurs
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56. Instruction Format Opcode Opcode Address Opcode Address1 Address2
Zero Address Instruction
Opcode
Address
One Address Instruction
Opcode
Address1
Address2
Two Address Instruction
Opcode
Address1
Address2
Address3
Three Address Instruction
Example:
X = (A + B) * (C + D)
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57. Three address instructions
ADD R1 , A , B R 1 <--M [ A ] + M [ B ]
ADD R2 , C , D R 2 <--M [ C ] + M [ D ]
MUL X , R1 , R2 M [ X ] <--R 1 * R 2
MOV R1 , A R 1 <--M [ A ]
ADD R1 , B R 1 <--R 1 + M [ B ]
MOV R2 , C R 2 <--M [ C ]
ADD R2 , D R 2 <--R 2 + M [ D ]
MUL R1 , R2 R 1 <--R 1 * R 2
MOV X , R1 M [ X ] <--R 1
Two address instructions
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58. One address instructions
LOAD A A C <- M [ A J
ADD B A C <- A C + M [ B ]
STORE T M [ T ] <- A C
LOAD C A C <- M [ C ]
ADD D A C <- A C + M [ D ]
MUL T A C <- A C • M [ T ]
STORE X M [ X ] <- A C
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59. Zero address instructions
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60. Stack Organization Block diagram of 64- word stack
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61. Subroutine Calls Requirements Set PC to arbitrary address
Return PC to instruction after call sequence
Handle nested subroutine calls
Save and restore caller’s registers
Pass an arbitrary number of arguments
Pass and return structures
Allocate and de-allocate space for local variables
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