Chapter 12: TRACE

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PERIOD Path

The detail path section shows all of the details for each path in the analyzed timing constraint. The most important thing it does is identify if the path meets the timing requirement. This information appears on the first line and is defined as the Slack. If the slack number is positive, the path meets timing constraint by the slack amount. If the slack number is negative, the path fails the timing constraint by the slack amount. Next to the slack number is the equation used for calculating the slack. The requirement is the time constraint number. In this case, it is 12 ns Because that is the time for the original timespec TS_wclk. The data path delay is 3.811 ns and the clock skew is negative 0.014 ns. (12 - (3.811 - 0.014) = 8.203). The detail paths are sorted by slack. The path with the least amount of slack, is the first path shown in the Timing Constraints section.

The Source is the starting point of the path. Following the source name is the type of component. In this case the component is a flip-flop (FF). The FF group also contains the SRL16. Other components are RAM (Distributed RAM vs BlockRAM), PAD, LATCH, HSIO (High Speed I/O such as the Gigabit Transceivers) MULT (Multipliers), CPU (PowerPC), and others. In Timing Analyzer, for FPGA designs the Source is a hot-link for cross probing. For more information on Cross Probing please see Cross Probing with Floorplanner.

The Destination is the ending point of the path. See the above description of the Source for more information about Destination component types and cross probing.

The Requirement is a calculated number based on the time constraint and the time of the clock edges. The source and destination clock of this path are the same so the entire requirement is used. If the source or destination clock was a related clock, the new requirement would be the time difference between the clock edges. If the source and destination clocks are the same clock but different edges, the new requirement would be half the original period constraint.

The Data Path Delay is the delay of the data path from the source to the destination. The levels of logic are the number of LUTS that carry logic between the source and destination. It does not include the clock-to-out or the setup at the destination. If there was a LUT in the same slice of the destination, that counts as a level of logic. For this path, there is no logic between the source and destination therefore the level of logic is 0.

The Clock Skew is the difference between the time a clock signal arrives at the source flip- flop in a path and the time it arrives at the destination flip-flop. If Clock Skew is not checked it will not be reported.

The Source Clock or the Destination Clock report the clock name at the source or destination point. It also includes if the clock edge is the rising or falling edge and the time that the edge occurs. If clock phase is introduced by the DCM/DLL, it would show up in the arrival time of the clock. This includes coarse phase (CLK90, CLK180, or CLK270) and fine phase introduced by Fixed Phase Shift or the initial phase of Variable Phase Shift

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Xilinx 8.2i manual Period Path
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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.
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