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Answers to Top FAQs
1. Signal Integrity Analysis with Third-Party Tools
2. Reviewing Printed Circuit Board Schematics with the Quartus® Prime Software
3. Siemens EDA PCB Design Tools Support
4. Cadence Board Design Tools Support
5. Quartus® Prime Pro Edition User Guide: PCB Design Tools Document Archives
A. Quartus® Prime Pro Edition User Guides
1.4.1. IBIS Model Access and Customization Flows
1.4.2. Elements of an IBIS Model
1.4.3. Customizing IBIS Models
1.4.4. Design Simulation Using the Siemens EDA HyperLynx* Software
1.4.5. Configuring LineSim to Use Intel IBIS Models
1.4.6. Integrating Intel IBIS Models into LineSim Simulations
1.4.7. Running and Interpreting LineSim Simulations
1.5.1. Supported Devices and Signaling
1.5.2. Accessing HSPICE Simulation Kits
1.5.3. The Double Counting Problem in HSPICE Simulations
1.5.4. HSPICE Writer Tool Flow
1.5.5. Running an HSPICE Simulation
1.5.6. Interpreting the Results of an Output Simulation
1.5.7. Interpreting the Results of an Input Simulation
1.5.8. Viewing and Interpreting Tabular Simulation Results
1.5.9. Viewing Graphical Simulation Results
1.5.10. Making Design Adjustments Based on HSPICE Simulations
1.5.11. Sample Input for I/O HSPICE Simulation Deck
1.5.12. Sample Output for I/O HSPICE Simulation Deck
1.5.13. Advanced Topics
1.5.12.1. Header Comment
1.5.12.2. Simulation Conditions
1.5.12.3. Simulation Options
1.5.12.4. Constant Definition
1.5.12.5. I/O Buffer Netlist
1.5.12.6. Drive Strength
1.5.12.7. Slew Rate and Delay Chain
1.5.12.8. I/O Buffer Instantiation
1.5.12.9. Board and Trace Termination
1.5.12.10. Double-Counting Compensation Circuitry
1.5.12.11. Simulation Analysis
2.1. Reviewing Quartus® Prime Software Settings
2.2. Reviewing Device Pin-Out Information in the Fitter Report
2.3. Reviewing Compilation Error and Warning Messages
2.4. Using Additional Quartus® Prime Software Features
2.5. Using Additional Quartus® Prime Software Tools
2.6. Reviewing Printed Circuit Board Schematics with the Quartus® Prime Software Revision History
4.1. Cadence PCB Design Tools Support
4.2. Product Comparison
4.3. FPGA-to-PCB Design Flow
4.4. Setting Up the Quartus® Prime Software
4.5. FPGA-to-Board Integration with the Cadence Allegro Design Entry HDL Software
4.6. FPGA-to-Board Integration with Cadence Allegro Design Entry CIS Software
4.7. Cadence Board Design Tools Support Revision History
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1.5.3.1. Defining the Double Counting Problem
The double counting problem is inherent to the difference between the method to analyze output timing in the Quartus® Prime software versus the method HSPICE models use. The timing analyzer tools in the Quartus® Prime software measure delay timing for an output signal from the core logic of the FPGA design through the output buffer, ending at the FPGA pin with a default capacitive load or a specified value for the I/O standard you selected. This measurement is the tCO timing variable.
Figure 11. Double Counting Problem
HSPICE models for board simulation measure tPD (propagation delay) from an arbitrary reference point in the output buffer, through the device pin, out along the board routing, and ending at the signal destination.
If you add these two delays, the delay between the output buffer and the device pin appears twice in the calculation. A model or simulation that does not account for this double count creates overly pessimistic simulation results, because the double-counted delay can limit I/O performance artificially.
One approach to fix the problem is subtracting the overlap between tCO and tPD to account for the double count. However, this adjustment is not accurate, because each measurement considers a different load.
Note: Input signals do not exhibit this problem, because the HSPICE models for inputs stop at the FPGA pin instead of at the input buffer. In this case, adding the delays together produces an accurate measurement of delay timing.