Built-In Real Nettypes

Cadence provides a pre-compiled SV Package (cds_rnm_pkg) of wreal-like nettypes, available for import. This allows you to reuse and migrate the Verilog-AMS code to SV. 

You can enable real number modeling in SystemVerilog by creating a set of built-in nettypes with real (scalar or typedef) data type and built-in resolution functions, equivalent to the wreal resolution functions. The SV built-in resolution functions and their equivalent wreal types are shown in the following table:

A built-in real SV nettype can be declared using the nettype command as follows:

nettype real wrealavg with CDS_res_wrealavg

Where:

wrealavg is the identifier that you use for nettype and CDS_res_wrealavg is a Cadence built-in resolution function.

You can also use another name for an existing built-in nettype, as shown below.

nettype real wrealavg with CDS_res_wrealavg; //declare a built-in nettype "wrealavg"

nettype wrealavg myWrealAvg; //rename wrealavg to myWrealAvg

Once a built-in nettype has been declared, a net of the built-in nettype can be used just like a net of any other user-defined nettype (UDN) as governed by the SV LRM.

nettype real wrealavg with CDS_res_wrealavg; //declare a built-in nettype "wrealavg"
wrealavg x;           //declare a singular net of nettype "wrealavg"
wrealavg x [0:3];    // declare a 4-element array of nets of nettype "wrealavg"

You can easily port existing wreal models to SV by using the cds_rnm_pkg package that defines a set of built-in nettypes that are equivalent to the typed wreal nets. For example, a simple Verilog-AMS wreal module

module real_model(x);

   input x [0:3];
   wrealavg x [0:3];
   child C(x);
endmodule

can be ported to use SV nettypes by simply importing the cds_rnm_pkg package, as shown below.

import cds_rnm_pkg::*;

module real_model(x);

   input x [0:3];
   wrealavg x [0:3];
   child C(x);
endmodule

The package is included in the Xcelium installation at $INSTALL_ROOT/tools/affirma_ams/etc/dms/cds_rnm_pkg.sv. When the software is installed, the package is compiled into a new INSTALL_ROOT/tools/affirma_ams/etc/dms/dmsLib directory. The package is automatically appended to the xrun command line and is available for import in all SV modules that xrun is compiling.

Related Topics

• Declaring Nettypes
• Examples of Using Built-In Nettypes