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PAR Process

PAR Process

This section provides information on how placing and routing are performed by PAR, as well as information on timing-driven PAR and automatic timespecing.

Placing

The PAR placer executes multiple phases of the placer. PAR writes the NCD after all the placer phases are complete.

During placement, PAR places components into sites based on factors such as constraints specified in the PCF file, the length of connections, and the available routing resources.

Routing

After placing the design, PAR executes multiple phases of the router. The router performs a converging procedure for a solution that routes the design to completion and meets timing constraints. Once the design is fully routed, PAR writes an NCD file, which can be analyzed against timing.

PAR writes a new NCD as the routing improves throughout the router phases.

Note: Timing-driven place and timing-driven routing are automatically invoked if PAR finds timing constraints in the physical constraints file. See the following section for details.

Timing-driven PAR

Timing-driven PAR is based on the Xilinx timing analysis software, an integrated static timing analysis tool that does not depend on input stimulus to the circuit. Placement and routing are executed according to timing constraints that you specify in the beginning of the design process. The timing analysis software interacts with PAR to ensure that the timing constraints imposed on your design are met.

To use timing-driven PAR, you can specify timing constraints using any of the following ways:

•Enter the timing constraints as properties in a schematic capture or HDL design entry program. In most cases, an NCF will be automatically generated by the synthesis tool.

•Write your timing constraints into a User Constraints File (UCF). This file is processed by NGDBuild when the logical design database is generated.

To avoid manually entering timing constraints in a UCF, use the Xilinx Constraints Editor, a tool that greatly simplifies creating constraints. For a detailed description of how to use the Constraints Editor, see the Constraints Editor online help included with the software.

•Enter the timing constraints in the physical constraints file (PCF), a file that is generated by MAP. The PCF file contains any timing constraints specified using the two previously described methods and any additional constraints you enter in the file.

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Xilinx 8.2i manual PAR Process, Placing, Routing, Timing-driven PAR
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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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