What is System Verilog DPI (Direct Programming Interface)

Direct programming interface or DPI is a interface between the System Verilog and the C language. It allows you to call the sytem verilog functions in C language and Vice Versa

why :

1. you can reuse your existing c code with system verilog

Sytem Verilog :

module hello();
    import "DPI-C" function void print_hello();

    initial
    begin
        print_hello();
    end

endmodule

C :

===

void print_hello() {
    printf("Hello World From C \n");
}

How to run :

    Step 1. Compile your C code
        gcc -shared -o hello.so hello.c
    Step 2. Compile your SV code
        vlog -sv hello.sv
    Step 3. link and load
        vsim -c hello -sv_lib hello
    Step 4. Run
        VSIM> run -all

    output :
        VSIM 1> run -all
        # Hello World From C
        # ** Note: $finish    : hello.sv(7)
        #    Time: 0 ns  Iteration: 0  Instance: /hello

GCC option :

-shared

Produce a shared object which can then be linked with other objects to form an executable.

Explanation :

In the above example we are calling a C funtion print_hello() in system

verilog code. Following are the points to note :

• we need to import the C function in system verilog with statement 'import "DPI-C"'
• we should have actual funtion implementiaon in C file
• Call the C funtion in your system verilog code
• remember to link library at loading time
• import declaration can occur anywhere where a SystemVerilog task or function definition is allowed

NOTE : C function should not comsume time like the system verilog functions

Imported Functions :

• Functions implemented in foreign language can be called in system verilog, such functions are called Imported functions

Exported Functions :

• System verilog functions that are called from foeign language should appear in exported function declerations