Verilog Procedural Interface

The Verilog Procedural Interface (VPI), originally known as PLI 2.0, is an interface primarily intended for the C programming language. It allows behavioral Verilog code to invoke C functions, and C functions to invoke standard Verilog system tasks. The Verilog Procedural Interface is part of the IEEE 1364 Programming Language Interface standard; the most recent edition of the standard is from 2005. VPI is sometimes also referred to as PLI 2, since it replaces the deprecated Program Language Interface (PLI).

While PLI 1 was depreciated in favor of VPI (aka. PLI 2). PLI 1 is still commonly used over VPI due to its much more widely documented tf_put, tf_get function interface that is described in many verilog reference books.