Forum Discussion

TAnde27's avatar
TAnde27
Icon for New Contributor rankNew Contributor
6 years ago
Solved

Why won't Quartus give me an error or warning for this obvious Verilog error during compilation?

Hi, In my Verilog HDL projects, it seems Quartus provides no notification (errors, warnings, or messages in the compilation log) if I accidentally declare a port as an input but then assign it with...
  • ak6dn's avatar
    ak6dn
    6 years ago

    This is why such tools as 'VeriLint' were developed that try to check the semantics of what your code is doing vs pure syntax.

    Your example has correct language syntax, but the semantics of what you are doing is not (necessarily) meaningful. It could be, or not.

    You can't expect the QuartusII verilog parser to figure these things out. VHDL language is much more strict, Verilog is looser.

AnandRaj_S_Intel's avatar
AnandRaj_S_Intel
Icon for Regular Contributor rankRegular Contributor
6 years ago

Hi Tyler,

Quartus can't report logical error.

Modules can be instantiated from within other modules.And can interface with input / output depending on Logic.

One question How to create a 2-bit counter?

Please refer module instantiation basic.

Example :Output of one DFF can be input to another.

module dff (clk, d, q);
input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
 
module top;
reg data, clock;
wire q_out, net_1;
  dff inst_1 (.d(data), .q(net_1), .clk(clock));
  dff inst_2 (.clk(clock), .d(net_1), .q(q_out));
endmodule

Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

Regards

Anand

TAnde27's avatar
TAnde27
Icon for New Contributor rankNew Contributor
6 years ago

Yes, but your example is quite different from the one I provided.

In my case, bitwise_negation_wrapper declares an *input* port y which is being internally driven by the instantiated module bitwise_negation. My question is why the compiler isn't complaining about a module driving it's own input port.

I recently read about "port coercion" in Verilog, and that may be what's going on here. Does anyone know if there is a way to have the compiler throw a warning for coerced ports?