The Tool Command Language (Tcl) is the scripting language integrated in the Vivado® tool environment. Tcl is a standard language in the semiconductor industry for application programming interfaces, and is used by Synopsys® Design Constraints (SDC).
SDC is the mechanism for communicating timing constraints for FPGA synthesis tools from Synopsys Synplify as well as other vendors, and is a timing constraint industry standard; consequently, the Tcl infrastructure is a “Best Practice” for scripting language.
Tcl lets you perform interactive queries to design tools in addition to executing automated scripts. Tcl offers the ability to “ask” questions interactively of design databases, particularly around tool and design settings and state. Examples are: querying specific timing analysis reporting commands live, applying incremental constraints, and performing queries immediately after to verify expected behavior without re-running any tool steps.
The following sections describe some of the basic capabilities of Tcl with Vivado.