how to model timing with interface method?

[Qian]

Hi, everyone.

I'm new to systemc and have some code as below. Slave module inherit and implement the write method of MyInterface, I have add a wait() statement to modeling the timing of write while get an error message saying "Error: (E519) wait() is only allowed in SC_THREADs and SC_CTHREADS: in SC_METHODS use next_trigger() instead".

So my question is how should I modeling timing with custom interface method? 

class Slave : public MyInterface, public sc_module {
  public:
    virtual void write(unsigned addr, char &data) {
      // slave takes 2 ns to finish
      wait(2, SC_NS);
      buf[addr] = data;
    }
}

Thank you for your comments!

[David Black]

The code you wrote suits SC_THREAD processes but will not work with SC_METHOD processes. SC_THREADs allow yielding (i.e., calls to wait()) whereas SC_METHODs must execute in zero time and do not allow for waits. If you change the calling process to an SC_THREAD, then this would work; however, there are likely other things that need to change.

If you can use C++11, one solution would be to spawn a lambda to create a temporary SC_THREAD disconnected from the caller.

class Slave : public MyInterface, public sc_module {
  public:
    void write(unsigned addr, char &data) override {
      spawn( [&](){
        // slave takes 2 ns to finish
        wait(2, SC_NS);
        buf[addr] = data;
      } );
    }
}

A lot of this depends on the calling code, which you have not provided. The above solution may not work depending on how your SC_METHOD uses the results.

 

[Qian]

Thank you for your explanation! Indeed the caller was a common C++ function, problem has been solved by using a SC_THREAD.