Logic Circuit Modeling

From what we have learnt in digital design, we know that there could be only two types of digital circuits. One is combinational circuits and the second is sequential circuits. There are very few rules that need to be followed to get good synthesis output and avoid surprises.

Constructs Not Supported in Synthesis

What is logic synthesis ?

Logic synthesis is the process of converting a high-level description of design into an optimized gate-level representation. Logic synthesis uses a standard cell library which have simple cells, such as basic logic gates like and,

Introduction Verilog PLI (Programming Language Interface) is a mechanism to invoke C or C++ functions from Verilog code. The function invoked in Verilog code is called a system call. An example of a built-in system call is $display, $stop, $random. PLI allows the user to create custom system calls, something that Verilog syntax does not allow us to do. Some of these are:- 

Passing Structure Example

DPI allows to pass the structs and Unions . This can be done by passing pointers or by packing.

In the following example, a "struct" is passed from SystemVerilog to C and also from C to Systemverilog using import and export functions.

Open Arrays

The size of the packed dimension, the unpacked dimension, or both dimensions can remain unspecified,such cases are referred to as open arrays (or unsized arrays). Open arrays allow the use of generic code to handle different sizes.

The SystemVerilog DPI supports only SystemVerilog data types, which are the data types that can cross the boundary between SystemVerilog and a foreign language in both the direction. On the other hand, the data types used in C code shall be C types. A value that is passed through the DPI is specified in SystemVerilog code as a value of SystemVerilog data type,

Import Methods

Methods implemented in C and given import declarations in SystemVerilog can be called from SystemVerilog, such methods are referred to as imported methods.Imported tasks or functions are similar to SystemVerilog tasks or functions.

Two Layers Of Dpi-C

DPI-C consists of two separate layers: the SystemVerilog layer and a foreign language layer. The SystemVerilog layer does not depend on which programming language is actually used as the foreign language.