Control Unit Design

Sections

Navigate through the learning materials and practice exercises.

1. 5

   Control Unit Design

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   The Control Unit (CU) is the essential component of the CPU that manages...

2. 5.1

   Introduction To Control Design

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   This section introduces the Control Unit (CU) as the critical component of...

3. 5.1.1

   Role Of The Control Unit: Generating Control Signals To Coordinate The Data Path

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   The Control Unit (CU) is vital in a CPU, generating control signals that...

4. 5.1.1.1

   The Choreographer

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   The Control Unit (CU) orchestrates operations within the CPU, translating...

5. 5.1.1.2

   Coordination And Synchronization

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   This section delves into the critical role of the Control Unit in...

6. 5.1.2

   Micro-Operations: Elementary Operations Performed By The Cpu In One Clock Cycle

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   This section delves into micro-operations, the smallest actions executed by...

7. 5.1.2.1

   Atomicity

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   This section explains atomicity in micro-operations, emphasizing that...

8. 5.1.2.2

   Internal Micro-Operations

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   This section discusses the internal micro-operations performed by the...

9. 5.1.2.2.1

   Pc -> Mar: Transfer The Content Of The Program Counter To The Memory Address Register

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   This section explains the operation of transferring the value from the...

10. 5.1.2.2.2

    A_reg -> Alu_input1: Transfer Data From An Internal Buffer Register 'a' To The Alu's First Input

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    This section focuses on the transfer of data from an internal buffer...

11. 5.1.2.2.3

    Alu_add_enable: Activate The Alu To Perform An Addition

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    This section explains the control signals generated by the Control Unit (CU)...

12. 5.1.2.2.4

    Result_alu -> R1: Transfer The Alu's Result To General Purpose Register R1

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    This section emphasizes the importance of transferring the result of...

13. 5.1.2.2.5

    Pc_increment: Increment The Program Counter

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    This section details the process of incrementing the Program Counter (PC)...

14. 5.1.2.3

    External Micro-Operations

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    This section covers external micro-operations, which are fundamental actions...

15. 5.1.2.3.1

    Memory_read_signal: Send A Signal To The Memory Controller To Perform A Read Operation

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    The Memory_READ_Signal is a crucial control signal generated by the Control...

16. 5.1.2.3.2

    Memory_write_signal: Send A Signal To The Memory Controller To Perform A Write Operation

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    The section details how the Control Unit (CU) sends a Memory_WRITE_Signal to...

17. 5.1.2.3.3

    I/o_device_select: Select A Specific I/o Device For Communication

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    This section explores the process of selecting specific I/O devices for...

18. 5.1.3

    Control Signals: Signals That Open/close Gates, Initiate Alu Operations, Etc.

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    Control signals are crucial electrical impulses generated by the Control...

19. 5.1.3.1

    Functionality Of Control Signals

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    Control signals are crucial electrical impulses generated by the Control...

20. 5.1.3.1.1

    Enable/disable

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    This section introduces the role of the Control Unit (CU) within a CPU,...

21. 5.1.3.1.2

    Select/route (Multiplexer Control)

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    The section on Select/Route (Multiplexer Control) outlines how the Control...

22. 5.1.3.1.3

    Initiate Operation

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    This section discusses the operational mechanisms of the Control Unit (CU),...

23. 5.1.3.1.4

    Memory/i/o Commands

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    This section explains the various memory and I/O commands that the Control...

24. 5.1.3.2

    Physical Transmission

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    This section describes the physical transmission of control signals within a...

25. 5.1.4

    Instruction Execution Steps: Sequence Of Micro-Operations For A Given Instruction

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    This section outlines how the Control Unit coordinates the execution of...

26. 5.1.4.1

    Typical Phases Of The Fetch-Decode-Execute Cycle (From Cu's Perspective)

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    This section outlines the key phases of the Fetch-Decode-Execute cycle as...

27. 5.1.4.1.1

    Fetch Cycle

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    The Fetch Cycle is a critical step in the CPU's operation where the Control...

28. 5.1.4.1.2

    Decode Cycle

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    The Decode Cycle section explores the Control Unit's process of interpreting...

29. 5.1.4.1.3

    Operand Fetch Cycle (If Needed)

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    The Operand Fetch Cycle occurs if an instruction requires operands not...

30. 5.1.4.1.4

    Execute Cycle

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    The Execute Cycle involves executing machine-level instructions, managing...

31. 5.1.4.1.5

    Memory Access/write Back Cycle (If Needed)

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    The **Memory Access/Write Back Cycle** is the final phase for instructions...

32. 5.2

    Instruction Sequencing And Interpretation

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    This section outlines the fundamental processes of instruction sequencing...

33. 5.2.1

    Instruction Fetch: Control Signals For Pc To Mar, Memory Read, Mdr To Ir

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    This section outlines the essential control signals involved in the...

34. 5.2.1.1

    Initiating Address Transfer (Pc To Mar)

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    This section explains how the Control Unit (CU) initiates the transfer of...

35. 5.2.1.2

    Requesting Memory Read

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    This section discusses the process of instruction fetching in the Control...

36. 5.2.1.3

    Capturing Memory Data (Mdr From Memory)

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    This section discusses the process of capturing memory data into the Memory...

37. 5.2.1.4

    Transferring To Instruction Register (Mdr To Ir)

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    This section outlines the critical process of transferring data from the...

38. 5.2.2

    Instruction Decode: Interpreting The Opcode And Addressing Mode Fields

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    This section focuses on how the Control Unit (CU) decodes instructions and...

39. 5.2.2.1

    Opcode Extraction

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    This section explains opcode extraction within the instruction decode...

40. 5.2.2.2

    Addressing Mode Interpretation

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    This section delves into how the Control Unit interprets machine...

41. 5.2.2.3

    Mapping To Microprogram/logic

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    This section discusses how high-level machine instructions are decoded and...

42. 5.2.2.3.1

    Hardwired Cu

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    This section elaborates on the architecture of Hardwired Control Units (CUs)...

43. 5.2.2.3.2

    Microprogrammed Cu

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    Microprogrammed control units offer flexibility in CPU design by storing...

44. 5.2.3

    Operand Fetch: Control Signals For Mar, Mdr, And Register File Access

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    This section discusses how the Control Unit generates control signals to...

45. 5.2.3.1

    Register Operands (Fastest)

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    This section details the process and significance of using register operands...

46. 5.2.3.2

    Memory Operands (Slower)

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    This section discusses the processes involved in fetching operands from...

47. 5.2.4

    Execute: Control Signals For Alu Operation And Register Writes

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    The **Execute Cycle** is where the actual computation occurs. The Control...

48. 5.2.4.1

    Alu Operation Selection

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    This section details how the Control Unit (CU) selects specific operations...

49. 5.2.4.2

    Result Generation And Status Flags

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    This section discusses how the Control Unit (CU) manages the execution of...

50. 5.2.4.3

    Result Write Back

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    This section details the process of writing back results to registers in CPU...

51. 5.2.5

    Branching And Jump Control: Modifying The Pc Based On Conditions

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    This section discusses how the Control Unit modifies the Program Counter for...

52. 5.2.5.1

    Unconditional Jump/call (Jump Address, Call Address)

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    The section explores unconditional jumps and calls in CPU instruction...

53. 5.2.5.2

    Conditional Branch (Beq Label, Bne Label, Etc.)

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    This section explores the mechanics of conditional branching in the CPU's...

54. 5.2.6

    Timing Signals: Generating Sequence Of Control Signals In Specific Time Intervals

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    This section discusses how the Control Unit utilizes timing signals to...

55. 5.3

    Hardwired Control - Design Methods And Cpu Control Unit

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    This section explores hardwired control units in CPU design, detailing how...

56. 5.3.1

    Concept: Control Signals Are Generated By Combinational Logic Circuits

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    Combinational logic circuits generate control signals that dictate the...

57. 5.3.1.1

    Combinational Logic

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    This section introduces the concept of combinational logic in the context of...

58. 5.3.1.2

    Sequential Logic (State Registers/flip-Flops)

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    This section delves into the role of sequential logic in control units,...

59. 5.3.1.3

    Direct Mapping

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    This section highlights the concept of hardwired control in CPU design,...

60. 5.3.1.4

    Analogy

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    This section highlights the analogy between the Control Unit (CU) in a CPU...

61. 5.3.2

    Input To Hardwired Control

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    This section describes the hardwired control unit, emphasizing its role in...

62. 5.3.3

    Output Of Hardwired Control

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    The hardwired control approach utilizes combinational logic circuits to...

63. 5.3.4

    Design Methods: How A Complex Hardwired Cu Is Systematically Constructed

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    This section discusses the systematic design methods employed in...

64. 5.3.4.1

    State Table Method (Finite State Machine - Fsm)

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    This section introduces the State Table Method as a systematic approach for...

65. 5.3.4.2

    Delay Element Method

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    The Delay Element Method represents a simplistic and rarely used design...

66. 5.3.5

    Advantages Of Hardwired Control

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    Hardwired control units provide rapid execution through fixed logic circuits...

67. 5.3.6

    Disadvantages Of Hardwired Control

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    Hardwired control units present significant challenges in terms of design...

68. 5.3.7

    Typical Application

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    This section discusses the typical applications of hardwired control in...

69. 5.4

    Microprogrammed Control - Basic Concepts

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    Microprogrammed control provides a flexible method for designing Control...

70. 5.4.1

    Concept: Control Signals Are Generated By A Sequence Of Microinstructions Stored In A Special Control Memory (Control Store - Cs Or Control Memory - Cm)

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    This section describes how control signals in a microprogrammed control unit...

71. 5.4.2

    Microinstruction: A Word In The Control Memory That Specifies One Or More Micro-Operations And The Address Of The Next Microinstruction

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    Microinstructions are fundamental components of microprogrammed control...

72. 5.4.3

    Microprogram: A Sequence Of Microinstructions That Define The Execution Of A Machine Instruction

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    Microprograms are sequences of microinstructions that execute machine...

73. 5.4.4

    Control Address Register (Car) / Microprogram Counter (Μpc)

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    The Control Address Register (CAR) and the Microprogram Counter (µPC) are...

74. 5.4.5

    Microinstruction Register (Mir)

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    The Microinstruction Register (MIR) temporarily holds microinstructions...

75. 5.4.6

    Sequencing Capabilities: Branching, Conditional Branching Within The Microprogram

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    This section discusses the sequencing capabilities of microprogrammed...

76. 5.5

    Microprogrammed Control - Minimizing Microinstruction Size And Multiplier Control Unit

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    This section discusses techniques for minimizing the size of...

77. 5.5.1

    Minimizing Microinstruction Size

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    This section discusses strategies for reducing the size of microinstructions...

78. 5.5.2

    Horizontal Microprogramming

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    Horizontal microprogramming utilizes wide microinstruction words, with each...

79. 5.5.3

    Vertical Microprogramming

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    Vertical microprogramming reduces the size of microinstructions by encoding...

80. 5.5.4

    Hybrid Approaches

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    Hybrid approaches in control unit design combine the speed of hardwired...

81. 5.5.5

    Multiplier Control Unit (Detailed Example)

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    This section provides a detailed example of designing a Microprogrammed...

82. 5.6

    Microprogrammed Computers - Cpu Control Unit

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    This section describes the architecture and operations of a microprogrammed...

83. 5.6.1

    Overall Structure Of A Microprogrammed Cpu Control Unit

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    This section describes the architecture of a Microprogrammed CPU Control...

84. 5.6.2

    Flow Of Control

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    This section covers the mechanisms of how the Control Unit orchestrates...

85. 5.6.3

    Advantages Of Microprogrammed Control

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    Microprogrammed control offers significant flexibility and adaptability in...

86. 5.6.4

    Disadvantages

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    This section discusses the disadvantages of hardwired control units in CPU...

87. 5.6.5

    Typical Application

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    This section discusses the typical applications of hardwired control in RISC...