Synchronous Circuit Analysis
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Synchronous Circuit Analysis

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Questions and Answers

What is the purpose of the set_false_path command in timing exceptions?

  • To specify the design's power requirements
  • To ignore certain paths during analysis (correct)
  • To increase the clock frequency
  • To analyze all paths in the design

    • Which command is used to indicate that a path may take more than one cycle?

  • set_case_analysis
  • set_multicycle_path (correct)
  • set_false_path
  • set_timing_analysis

    • What would be the effect of executing the command set_case_analysis 1 [get_ports SLEEP_MODE]?

  • Disable the SLEEP_MODE functionality
  • Assign a constant value to the SLEEP_MODE pin (correct)
  • Enable all pins for dynamic analysis
  • Delay the timing analysis

    • In the context of timing exceptions, what does the option -hold signify when using set_multicycle_path?

    <p>Specifies timing constraints for hold</p> Signup and view all the answers

    Which of the following is NOT a purpose of the commands discussed in the content?

    <p>To optimize design for power consumption</p> Signup and view all the answers

    What is the setup slack for the timing end-point FF1/D?

    <p>755 ps</p> Signup and view all the answers

    What is the calculated hold slack at the timing end-point FF1/D?

    <p>190 ps</p> Signup and view all the answers

    What clock period was used in the calculations in this content?

    <p>1000 ps</p> Signup and view all the answers

    What is the required time at the timing end-point port Z?

    <p>875 ps</p> Signup and view all the answers

    What is the arrival time at the timing end-point port Z?

    <p>70 ps</p> Signup and view all the answers

    What does the command 'set_clock_latency' specify?

    <p>The delay of clock edges from the ideal value</p> Signup and view all the answers

    Which command is used to create a clock signal?

    <p>create_clock</p> Signup and view all the answers

    What is modeled by clock uncertainty in a circuit design?

    <p>Jitter and skew in signal edges</p> Signup and view all the answers

    What does the command 'set_clock_uncertainty 15 -hold' specify about a clock signal?

    <p>An uncertainty of 15 units during hold time</p> Signup and view all the answers

    What is the purpose of 'set_clock_transition' in clock signal attributes?

    <p>To define the time taken for the clock signal to transition</p> Signup and view all the answers

    Which aspect does the environment of design add constraints to?

    <p>Signal timing at input and output ports</p> Signup and view all the answers

    What must be checked at the output port concerning setup/hold requirements?

    <p>Setup and hold time violations</p> Signup and view all the answers

    What does the term 'jitter' refer to in the context of clock uncertainty?

    <p>The temporal variation of clock edges</p> Signup and view all the answers

    What is the primary purpose of Shannon expansion in digital circuit design?

    <p>To restructure for improved circuit delay.</p> Signup and view all the answers

    In the context of timing-driven optimization, what does 'retiming' involve?

    <p>Balancing the amount of logic between registers.</p> Signup and view all the answers

    Which of the following best describes fanout optimization?

    <p>Inserting buffers in high-fanout nets.</p> Signup and view all the answers

    Given the setup time of 45 ps and the setup slack must be computed, which timing factor contributes to setup time analysis?

    <p>CLK-to-Q delay of the flip-flop.</p> Signup and view all the answers

    What should be the approach to improve the worst-case delay in a timing-driven optimization process?

    <p>Identify and restructure the critical paths.</p> Signup and view all the answers

    What is represented by the terms 'setup time' and 'hold time' in synchronous circuits?

    <p>Minimum time requirements for flip-flops for data capture.</p> Signup and view all the answers

    In designing a circuit with the constraints set in the SDC file, what does 'set_output_delay' define?

    <p>Delay for the output signals after the clock edge.</p> Signup and view all the answers

    If the arrival time for signal Z is 145 ps and for signal C is 130 ps, what can be inferred about the circuits' performance?

    <p>Signal Z has a higher propagation delay than signal C.</p> Signup and view all the answers

    What are the two approaches to technology mapping described?

    <p>Structural Mapping</p> Signup and view all the answers

    What happens to the delay when a smaller cell is replaced with a larger cell in timing-driven optimization?

    <p>Delay decreases</p> Signup and view all the answers

    What is the effect of replacing a cell C1 with a larger equivalent cell C2 during resizing?

    <p>Output slew of the driver increases</p> Signup and view all the answers

    What is the primary goal of timing-driven optimization when it comes to rewiring?

    <p>To reduce the overall path delay</p> Signup and view all the answers

    In the context of resizing, what assertion is true regarding cell functionalities?

    <p>Cells can be functionally equivalent yet of different sizes</p> Signup and view all the answers

    What is a consequence of moving a timing-critical signal closer to the sink?

    <p>Reduced overall path delay</p> Signup and view all the answers

    Which of the following can be a result of increasing the size of a cell during timing-driven optimization?

    <p>May increase the delay of the cells in its fanout</p> Signup and view all the answers

    What are the libraries structured to contain in the context of resizing?

    <p>Cells of the same functionality but different sizes</p> Signup and view all the answers

    Study Notes

    Synchronous Circuit Analysis - Setup & Hold Slack

    • Synchronous Circuit: The circuit uses flip-flops (FF1 and FF2) synchronized by a clock signal.
    • Timing Parameters:
      • Setup time: 45ps for both FF1 and FF2
      • Hold time: 10ps for both FF1 and FF2
      • CLK-to-Q delay: 20ps for both FF1 and FF2
      • Inverter delay: 50ps for each inverter (G1, G2, G3)
    • SDC Constraints:
      • Clock Period: 1000ps (defined by create_clock -name CLK -period 1000)
      • Input Delay: 150ps at input port A (defined by set_input_delay -clock [get_clocks CLK] 150 [get_ports A])
      • Output Delay: 125ps at output port Z (defined by set_output_delay -clock [get_clocks CLK] 125 [get_ports Z])

    Setup Slack at FF1/D

    • Arrival time at FF1/D: 150ps (input delay) + 50ps (inverter G1 delay) = 200ps
    • Required time at FF1/D: 1000ps (clock period) - 45ps (setup time) = 955ps
    • Setup slack at FF1/D: 955ps (required time) - 200ps (arrival time) = 755ps

    Hold Slack at FF1/D

    • Arrival time at FF1/D: 200ps (as calculated previously)
    • Required time at FF1/D: 10ps (hold time)
    • Hold slack at FF1/D: 200ps (arrival time) - 10ps (required time) = 190ps

    Setup Slack at Output Port Z

    • Arrival time at Z: 20ps (CLK-to-Q delay) + 50ps (inverter G3 delay) = 70ps
    • Required time at Z: 1000ps (clock period) - 125ps (output delay) = 875ps
    • Setup slack at Z: 875ps (required time) - 70ps (arrival time) = 805ps

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    Description

    This quiz covers the analysis of synchronous circuits, focusing on setup and hold slack calculations. It includes critical timing parameters such as setup time, hold time, and inverter delays while applying SDC constraints. Test your understanding of these concepts through practical calculation examples.

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