NetGen, Schematic-Based Simulation

Chapter 2: Design Flow

NetGen

NetGen is a command line program that distributes information about delays, setup and hold times, clock to out, and pulse widths found in the physical NCD design file back to the logical NGD file and generates a Verilog or VHDL netlist for use with supported timing simulation, equivalence checking, and static timing analysis tools.

NetGen reads an NCD as input. The NCD file can be a mapped-only design, or a partially or fully placed and routed design. An NGM file, created by MAP, is an optional source of input. NetGen merges mapping information from the optional NGM file with placement, routing, and timing information from the NCD file.

Note: NetGen reads an NGA file as input to generate a timing simulation netlist for CPLD designs.

See Chapter 22, “NetGen” for detailed information.

Schematic-Based Simulation

Design simulation involves testing your design using software models. It is most effective when testing the functionality of your design and its performance under worst-case conditions. You can easily probe internal nodes to check the behavior of your circuit, and then use these results to make changes in your schematic.

Simulation is performed using third-party tools that are linked to the Xilinx Development System. Use the various CAE-specific interface user guides, which cover the commands and features of the Xilinx-supported simulators, as your primary reference.

The software models provided for your simulation tools are designed to perform detailed characterization of your design. You can perform functional or timing simulation, as described in the following sections.

Functional Simulation

Functional simulation determines if the logic in your design is correct before you implement it in a device. Functional simulation can take place at the earliest stages of the design flow. Because timing information for the implemented design is not available at this stage, the simulator tests the logic in the design using unit delays.

Note: It is usually faster and easier to correct design errors if you perform functional simulation early in the design flow.

You can use integrated and non-integrated simulation tools. Integrated tools, such as Mentor Graphics or Innoveda, often contain a built-in interface that links the simulator and a schematic editor, allowing the tools to use the same netlist. You can move directly from entry to simulation when using a set of integrated tools.

Functional simulation in schematic-based tools is performed immediately after design entry in the capture environment. The schematic capture tool requires a Xilinx Unified Library and the simulator requires a library if the tools are not integrated. Most of the schematic-based tools require translation from their native database to EDIF for implementation. The return path from implementation is usually EDIF with certain exceptions in which a schematic tool is tied to an HDL simulator.

www.xilinx.com

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 NetGen, Schematic-Based Simulation

Models: 8.2i