Intel® Quartus® Prime Pro Edition User Guide: Design Optimization
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5.5.8. I/O Timing Optimization Techniques
This stage of design optimization focuses on I/O timing, including setup delay (tSU), hold time (tH), and clock-to-output (tCO) parameters.
- The design's assignments follow the suggestions in the Initial Compilation: Required Settings section of the Design Optimization Overview chapter.
- Resource utilization is satisfactory.
Summary of Techniques for Improving Setup and Clock-to-Output Times
The table lists the recommended order of techniques to reduce tSU and tCO times. Reducing tSU times increases hold (tH) times.
Order | Technique | Affects tSU | Affects tCO |
---|---|---|---|
1 | Verify of that the appropriate constraints are set for the failing I/Os (refer to Initial Compilation: Required Settings) | Yes | Yes |
2 | Use timing-driven compilation for I/O (refer to Fast Input, Output, and Output Enable Registers) | Yes | Yes |
3 | Use fast input register (refer to Programmable Delays) | Yes | N/A |
4 | Use fast output register, fast output enable register, and fast OCT register (refer to Programmable Delays) | N/A | Yes |
5 | Decrease the value of Input Delay from Pin to Input Register or set Decrease Input Delay to Input Register = ON | Yes | N/A |
6 | Decrease the value of Input Delay from Pin to Internal Cells or set Decrease Input Delay to Internal Cells = ON | Yes | N/A |
7 | Decrease the value of Delay from Output Register to Output Pin or set Increase Delay to Output Pin = OFF (refer to Fast Input, Output, and Output Enable Registers) | N/A | Yes |
8 | Increase the value of Input Delay from Dual-Purpose Clock Pin to Fan-Out Destinations (refer to Fast Input, Output, and Output Enable Registers) | Yes | N/A |
9 | Use PLLs to shift clock edges | Yes | Yes |
10 | Increase the value of Delay to output enable pin or set Increase delay to output enable pin (refer to Use PLLs to Shift Clock Edges) | N/A | Yes |