Using sc_trace inside SC_THREAD

[Nithin]

Hi,

I am trying to dump internal signals of an SC_MODULE's processes (SC_THREAD process) in a VCD. SC_MODULE has multiple processes and I need to dump signals from each of those processes in the same VCD. 

Currently, I am trying with one SC_THREAD process and I see this error when I add sc_trace inside the while loop:

Error: (E720) sc_trace_file already initialized: sc_trace() failed:
    No traces can be added to 'traces.vcd' once trace recording has started.
    To add tracing of 'A_val', create a new trace file.
In file: ../../../src/sysc/tracing/sc_trace_file_base.cpp:239
 

Here is my code:

SC_MODULE (SUM) {
  sc_in<sc_int<10>> A;
  sc_in<sc_int<10>> B;
  sc_out<sc_int<10>> S;
  sc_trace_file* Tf;

  void do_sum();
  SC_CTOR (SUM) {
      Tf = sc_create_vcd_trace_file("traces");
    SC_THREAD(do_sum);
        sensitive << A << B;
  }
  ~SUM() {
  sc_close_vcd_trace_file(Tf);
  }
};

void SUM::do_sum() {
    int A_val, B_val, S_val;
    while(true) {
    wait();
    A_val = A.read();
    B_val = B.read();
    S.write(A.read()+B.read());
    S_val = A_val + B_val;

    sc_trace(Tf, A_val, "A_val");
    sc_trace(Tf, B_val, "B_val");
    sc_trace(Tf, S_val, "S_val");
    }
  }

 

Can someone please help me with this?

Thanks in advance.

Regards,

Nithin

[David Black]

You’re only allowed to call sc_trace one time for each variable and after that tracing is automatic. So you need to move the sc_trace calls out into the constructor or into end_of_elaboration or somewhere else before simulation starts. You also need to move your local variables in to the class as members.

[Nithin]

Got it. Thank you David.