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Questions and Answers
What distinguishes microprogrammed control from hardwired control?
What distinguishes microprogrammed control from hardwired control?
Which type of control is more flexible in terms of making changes or modifications?
Which type of control is more flexible in terms of making changes or modifications?
What is a drawback of microprogrammed control in terms of operational speed?
What is a drawback of microprogrammed control in terms of operational speed?
Which aspect makes microprogrammed control advantageous for making modifications?
Which aspect makes microprogrammed control advantageous for making modifications?
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What is a key characteristic of hardwired control in its implementation?
What is a key characteristic of hardwired control in its implementation?
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Why does microprogrammed control offer more flexibility compared to hardwired control?
Why does microprogrammed control offer more flexibility compared to hardwired control?
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What is the purpose of the control unit in a digital system?
What is the purpose of the control unit in a digital system?
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How are the control variables represented at any given time in a digital system?
How are the control variables represented at any given time in a digital system?
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What is a microprogrammed control unit?
What is a microprogrammed control unit?
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What is each word in the control memory called in microprogrammed control?
What is each word in the control memory called in microprogrammed control?
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What does the Control Address Register (CAR) specify in a microprogrammed control system?
What does the Control Address Register (CAR) specify in a microprogrammed control system?
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How is the location of the next microinstruction generated in microprogrammed control?
How is the location of the next microinstruction generated in microprogrammed control?
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What is one of the typical functions of a microprogrammed sequencer?
What is one of the typical functions of a microprogrammed sequencer?
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What does the microinstruction do to initiate control operations?
What does the microinstruction do to initiate control operations?
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In microprogrammed control, what does the microprogram counter (µPC) typically do?
In microprogrammed control, what does the microprogram counter (µPC) typically do?
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What controls the sequence and branching in a microprogrammed control unit?
What controls the sequence and branching in a microprogrammed control unit?
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What is the purpose of the microinstruction register (µIR) in microprogramming?
What is the purpose of the microinstruction register (µIR) in microprogramming?
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Which component receives a new address at any given clock pulse transition in microprogrammed control?
Which component receives a new address at any given clock pulse transition in microprogrammed control?
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Study Notes
Control Unit Design
- The logic design of a digital system can be divided into two parts: Data path design (Data Processor) and Control Unit design.
Data Path Design
- Deals with the design of digital circuits that perform data processing operations (Arithmetic, logic, shift operations)
Control Unit Design
- Deals with the design of the control circuit that supervises the operations and determines the sequence in which they are executed.
Hardwired Control
- Uses fixed logic circuits to generate control signals
- Advantage: Fast mode of operation
- Disadvantage: Requires changes in wiring among various components if the design has to be modified
Microprogrammed Control
- The control information is stored as 1's and 0's in a special memory
- Advantage: More flexible, changes can be made by changing the contents of the memory
- Disadvantage: Slow mode of operation, extra hardware cost
Microprogrammed Control Unit
- A control unit whose binary control variables are stored in a memory
- Each word in control memory is called a microinstruction
- A sequence of microinstructions constitutes the microprogram
- The control memory can be either a ROM or RAM
Generation of Microprogrammed Control
- Control address register (CAR) or Microprogram Counter (µPC): specifies the address of the microinstruction
- Control data register (CDR) or Microinstruction Register (µIR): holds the microinstruction read from memory
- The location of the next microinstruction is generated by the sequencer
Microprogrammed Sequencer
- Typical functions: increment the control address register (CAR) by one, transfer an external address into CAR, load an initial address into CAR to start the control operations
Microprogrammed Control Unit Components
- Microprogram Counter (µPC)
- Control Memory (CM)
- Microinstruction Register (µIR)
- Decoder
- Data processing unit
- External Conditions
- External Address
- MUX
Microprogram Example
- Example of a microprogrammed control unit with external conditions and addresses
- Microprogram consists of microinstructions with control signals to the decoder and data processing unit
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Description
This quiz covers the concept of microprogrammed control in digital systems, focusing on the purpose of the control unit, generating control words, and programming control words to initiate various components in a data processor.
