Timing Verification with Trace, Net Delay Constraints

Chapter 12: TRACE

Timing Verification with TRACE

TRACE checks the delays in the input NCD file against your timing constraints. If delays are exceeded, TRACE issues the appropriate timing error.

Note: Xilinx recommends limiting timing constraint values to 2 ms (milliseconds). Timing Constraint values more than 2 ms may result in bad values in the timing report.

Net Delay Constraints

When a MAXDELAY constraint is used, the delay for a constrained net is checked to ensure that the routedelay is less than or equal to the NETDELAY constraint.

routedelay ≤ netdelayconstraint

ROUTEDELAY is the signal delay between the driver pin and the load pins on a net. This is an estimated delay if the design is placed but not routed.

Any nets with delays that do not meet this condition generate timing errors in the timing report.

Net Skew Constraints

When using USELOWSKEWLINES or MAXSKEW constraints or “–skew (Analyze Clock Skew for All Clocks)”, signal skew on a net with multiple load pins is the difference between minimum and maximum load delays.

signalskew = (maxdelay - mindelay)

MAXDELAY is the maximum delay between the driver pin and a load pin.

MINDELAY is the minimum delay between the driver pin and a load pin.

Note: Register-to-register paths included in a MAXDELAY constraint report undergo a hold violation (race condition) check only for paths whose start and endpoints are registered on the same clock edge.

For constrained nets in the PCF, skew is checked to ensure that the SIGNALSKEW is less than or equal to the MAXSKEW constraint.

signalskew ≤ maxskewconstraint

If the skew exceeds the maximum skew constraint, the timing report shows a skew error.

Path Delay Constraints

When a PERIOD constraint is used, the pathdelay equals the sum of logic (component) delay, route (wire) delay, and setup time (if any), minus clock skew (if any).

pathdelay = logicdelay + routedelay + setuptime - clockskew

The delay for constrained paths is checked to ensure that the pathdelay is less than or equal to the MAXPATHDELAY constraint.

pathdelay ≤ maxpathdelayconstraint

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Development System Reference Guide

8.2i specifications

Xilinx 8.2i is a significant version of the Xilinx ISE (Integrated Software Environment) that emerged in the early 2000s, marking an important milestone in the world of FPGA (Field-Programmable Gate Array) development. This version introduced a slew of advanced features, technologies, and characteristics that made it an indispensable tool for engineers and developers in designing, simulating, and implementing digital circuits.

One of the standout features of Xilinx 8.2i is its enhanced design entry capabilities. This version supports multiple design entry methods, including schematic entry, VHDL, and Verilog HDL, giving engineers the flexibility to choose their preferred approach. The integrated environment provides user-friendly graphical interfaces, making it accessible for both novice and experienced users.

Xilinx 8.2i's synthesis tools have been improved to enable more efficient design compilation and optimization. The new algorithms used in this version facilitate faster synthesis times while reducing power consumption and improving performance. Furthermore, it features support for advanced FPGA architectures, which allows for the implementation of more complex designs with greater efficiency.

The implementation tools in Xilinx 8.2i include advanced place and route capabilities, utilizing state-of-the-art algorithms for optimized resource usage. These tools enable designers to make better use of FPGA resources, ensuring that designs fit within the constraints of the target device while maximizing performance.

Another key characteristic of Xilinx 8.2i is its extensive support for various Xilinx devices such as the Spartan, Virtex, and CoolRunner series. This compatibility ensures that developers can leverage the powerful features of these FPGA families, including high-speed transceivers and DSP slices.

Xilinx 8.2i also places a strong emphasis on simulation and verification. The version integrates with various simulation tools, allowing for thorough testing of the designs before implementation. This reduces the risk of errors and ensures that the final product meets specifications.

In addition, this version includes support for design constraints, enabling engineers to specify timing, area, and other critical design parameters. By accommodating constraints, Xilinx 8.2i helps in achieving reliable and efficient designs tailored to project needs.

In summary, Xilinx 8.2i is a robust software development tool that enhances the design process for FPGAs. Its comprehensive features, including multiple design entry options, advanced synthesis and implementation tools, extensive device support, and strong simulation capabilities, make it a valuable resource for engineers and developers striving for innovation in digital design.

Xilinx 8.2i manual Timing Verification with Trace, Net Delay Constraints, Net Skew Constraints

Models: 8.2i