Netlist Modifying Commands - 2023.1 English

Vivado Design Suite User Guide: Implementation (UG904)

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2023.1 English

The following commands allow you to modify an existing netlist:

Note: For more information about these Tcl commands, see the Vivado Design Suite Tcl Command Reference Guide (UG835), or type <command> -help.

The netlist modifying commands work on a post-synthesis, post-place or post-route netlist. Before the netlist is modified, it must be loaded into memory. The netlist modifying commands allow you to make logical changes to the netlist when it is in memory. You can use the write_checkpoint command to save changes.

Tip: The Vivado tools allows you to make netlist changes unconditionally using the netlist modifying commands. However, logical changes can lead to invalid physical implementation. It is recommended to run DRCs after performing your netlist changes. In addition, DRCs are run as part of the process of adding the logical changes to the physical implementation. These DRCs flag any invalid netlist changes or new physical restrictions that need to be addressed before physical implementation can commence.

Logical changes are reflected in the schematic view as soon as the netlist modifying commands are executed. The following figure shows an example of a cell that was created using a LUT1 as a reference cell.

Figure 1. Cell Created Using LUT1 as a Reference Cell

When the output of the LUT1 is connected to an OBUF, the schematic reflects this change showing the ECO_INV/O pin no longer with a "no-connect." The following figure shows the resulting schematic view.

Figure 2. Schematic After Connection of LUT1 to an OBUF