How to implement adding function using next_trigger in SC_METHOD?

[Minu]

I am beginner in SystemC. I have implemented add() function using SC_THREAD(while loop and wait()).I am printing output on log after 2ns.How can I achieve this using SC_METHOD and next_trigger?

Code link using SC_THREAD:https://www.edaplayground.com/x/JSU8

Code link using SC_METHOD: https://www.edaplayground.com/x/wsBv

Please help I am stuck over this.

[David Black]

void add() {

  next_trigger(2,SC_NS);

  y=a+b;

}

or

void add() {

  y=a+b;

  next_trigger(2,SC_NS);

}

because next_trigger is non-blocking 

[Minu]

Hi @David Black,

Thanks for answering my question.

This I have implemented earlier but in this way I am not getting correct out.

MY testbench input is 

@0ns a=0     b=0. Out=0

@5ns a=5.     b=0. Out=5

@8ns a=5.     b=10 out=15

@15ns a=7.     b=7 out=14

And I should get output after 2ns so the output will be appear at 

@0ns a=0     b=0. Out=0

 

@7ns a=5.     b=0. Out=5

 

@10ns a=5.     b=10 out=15

 

@17ns a=7.     b=7 out=14

Above code is not fulfilling this requirement.

It would be great if you provide some insights on this requirement.

[karthickg]

The code that uses SC_THREAD has two waits:

  while(1){
    wait();//wait for sensitive list to occur
   	wait(2,SC_NS);
      		cout<<"\nWriting on out,at time"<<sc_time_stamp();

  	out.write(a.read()+b.read());
  }

The first `wait` blocks until one of the entries in its static sensitivity fires:

    SC_THREAD(adding);
    sensitive<<a;
    sensitive<<b;

The SC_METHOD replacement has only a single `next_trigger` - so it is not equivalent to the earlier implementation:

  int c;
  c=a.read()+b.read();
  out.write(c);
  next_trigger(2,SC_NS);

You need to implement a state machine in the SC_METHOD using next_triggers if you want the same behavior. Check this post for example: