The feature to create a node-level persistent source file in Verilog Quartus Mapping (VQM) format was introduced in the Quartus® II software to support back-annotation of node placement assignments for placement and performance preservation in incremental design flows. Back-annotation of the previous Fitter results creates an assignment to each node name in the design, and a post-synthesis VQM file provides a persistent source file with fixed node names.
Beginning with the introduction of the full incremental compilation feature in the Quartus II software version 5.0, logic location back-annotation is no longer a recommended design flow. Use the incremental compilation feature to preserve Fitter results to reduce compilation time and enable performance preservation. Incremental compilation does not use assignments to preserve locations; it reuses the post-fitting netlist database.
If you wanted to use a VQM file so that you could send someone your design without sending your source HDL design files, refer to the Related Solutions section below for better alternatives.
VQM files generated by the Quartus II software do not correctly support settings or assignments that might be included in the HDL source code such as in MegaWizard®-generated megafunction variations. (Note that VQM files generated by third-party synthesis tools work correctly.)
For the above reasons, the VQM-generation capability is available only for backwards-compatibility for older device families, where designers may have used back-annotation and VQM files to preserve placement:
- For designs targetting Cyclone® III devices, Stratix® III devices, and all newer device families, the Start VQM Writer command and the Settings dialog box option Save a node-level netlist of the entire design into a persistent source file (This option specifies VQM File name for full compilation and Start VQM Writer command) are not available and appear grayed out.
- For Stratix II GX designs, the VQM writer issues an error if your design includes the alt2gxb megafunction for a transceiver block. VQM files do not function correctly for designs with transceiver blocks due to assignments in the MegaWizard-generated megafunction variation that are not included in the VQM file.
For more information on preserving your compilation results with incremental compilation, refer to the Quartus II Incremental Compilation for Hierarchical & Team-Based Design (PDF) chapter in volume 1 of the Quartus II Handbook.