Multi-Level Circuit Analyzer

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Description

This MicroSim provides an interactive visualization of signal propagation through multi-level logic circuits. Students can select different circuit configurations, adjust individual gate delays, and watch an animation showing how signals travel through successive gate levels. The critical path — the longest delay path from any input to the output — is highlighted in red, revealing the bottleneck that limits the maximum operating frequency.

Key Features

  • ● Multiple circuit configurations: Choose from different multi-level topologies
  • ● Adjustable gate delays: Set individual delays to explore technology effects
  • ● Signal propagation animation: Watch signals travel level by level
  • ● Critical path highlighting: Longest delay path shown in red
  • ● Total delay readout: Cumulative propagation delay from input to output

Learning Objectives

Bloom Level: Evaluate (L5)

After using this MicroSim, students will be able to:

  • ✓ Define propagation delay and explain how it accumulates through multiple gate levels
  • ✓ Identify the critical path as the longest input-to-output delay path
  • ✓ Calculate total propagation delay by summing gate delays along the critical path
  • ✓ Evaluate the tradeoff between circuit depth and propagation delay
  • ✓ Explain why two-level implementations have shorter delay but may require more gates

How to Use

  1. Select a circuit configuration to load a multi-level circuit
  2. Adjust gate delays using the controls
  3. Click "Animate" to start the signal propagation animation
  4. Watch signals travel from inputs through each gate level to the output
  5. Identify the critical path highlighted in red
  6. Read the total propagation delay displayed for the critical path
  7. Click "Reset" to try different delay configurations

Lesson Plan

Before the Simulation (5 minutes)

  • Define propagation delay for a single logic gate
  • Explain that total circuit delay depends on the path through the most gate levels
  • Introduce the concept of critical path as the timing bottleneck

During the Simulation (15 minutes)

  1. Load the default circuit configuration and observe its structure
  2. Run the animation with default gate delays and note the critical path
  3. Record the total propagation delay
  4. Change one gate's delay and re-run to see if the critical path shifts
  5. Try a different circuit configuration and identify its critical path
  6. Compare circuits with different depths (2-level vs. 3-level vs. 4-level)

After the Simulation (5 minutes)

  • Discuss the speed vs. area tradeoff: two-level circuits are faster but may use more gates
  • Introduce the concept of maximum clock frequency as 1 / (critical path delay)
  • Connect to the motivation for multi-level optimization in synthesis tools

References