CODEWITHSUNDEEP
system-veriloguvm
RayaneCTX
RayaneCTX

Reputation: 593

Virtual interface element uses an interface with interface ports [warning from QuestaSIM vlog/vsim]

What is the meaning of the following warning issued by QuestaSIM's vsim? What is the simulator worried about here? I haven't been able to produce an actual simulation error from this yet.

My guess: it has something to do with interface instances vs. virtual interface instances, but my understanding is minimal.

** Warning: (vsim-8887) tests/base_test.svh(28): Virtual interface element 'this.apb_driver_bfm_vi.clk' uses an interface with interface ports.

apb_driver_bfm_vi is a virtual interface handle to the following interface:

interface apb_driver_bfm(
    input logic clk,
    input logic nrst,
    apb_if.apb_s apb_if_i // apb_if is itself an interface, apb_s is a modport.
);

endinterface : apb_driver_bfm

The virtual interface is used as follows: @(posegde apb_driver_bfm_vi.clk); in the run_phase of my testbench. This seems to work fine, despite the warning.

Upvotes: 0

Views: 869

Answers (1)

dave_59
dave_59

Reputation: 42616

From section 25.9 Virtual interfaces in the IEEE 1800-2017 SystemVerilog LRM

Although an interface may contain hierarchical references to objects outside its body or ports that reference other interfaces, it shall be illegal to use an interface containing those references in the declaration of a virtual interface.

this a problem when the interface port gets connected to a parameterized interface and different instances of the virtual interface have different parameterizations. This is not a problem when the interfaces have the same parameters, but the LRM is overly pessimistic.

Upvotes: 1

Related Questions