NGDBuild

NGDBuild performs all the steps necessary to read a netlist file in XNF or EDIF format and create an NGD file describing the logical design (a logical design is in terms of logic elements such as AND gates, OR gates, decoders, flip-flops, and RAMs). The NGD file resulting from an NGDBuild run contains both a logical description of the design reduced to Xilinx NGD (Native Generic Database) primitives and a description in terms of the original hierarchy expressed in the input netlist. The output NGD file can be mapped to the desired device family.

The following figure is a simplified drawing of the design flow through NGDBuild. NGDBuild invokes other programs and generates intermediate (NGO) files that are not shown in the drawing. For a complete description of how NGDBuild works, see the “EDIF2NGD, XNF2NGD, and NGDBuild” appendix.

Figure 4.1 NGDBuild Design Flow

Converting a Netlist to an NGD File

NGDBuild performs the following steps to convert a netlist to an NGD file (see the preceding figure). The netlist readers incorporate NCF files associated with each netlist. NCF files contain timing and layout constraints for each module.

Note: This procedure, the Netlister Launcher, and the netlist reader programs are described in more detail in the “EDIF2NGD, XNF2NGD, and NGDBuild” appendix.

1. Reads the source netlist.
   
   NGDBuild invokes the Netlister Launcher which determines the type of the input netlist and starts the appropriate netlist reader program.
   
   
2. Reduces all components in the design to NGD primitives.
   
   NGDBuild merges components that reference other files. NGDBuild also finds the appropriate system library components, physical macros (NMC files) and behavioral models.
   
   
3. Checks the design by running a Logical DRC (Design Rule Check) on the converted design.
   
   The Logical DRC is a series of tests on the logical design. It is described in “The Logical Design Rule Check” chapter.
   
   
4. Writes an NGD file as output.