anchor.diff:  
   interface FibIndication;
       method Action fibresult(Bit#(32) v);
  -    method Action fibnote(Bit#(32) v);
   endinterface
   
   interface FibRequest;
  
positive.code:    rule fibcomplete (frame.pc == FIBSTATECOMPLETE);
        //$display("FIBSTATECOMPLETE %d %d", frame.args, fibretval);
        indication.fibresult(zeroExtend(fibretval));
        frame.nextpc(FIBSTATEIDLE);
     endrule
     
     method Action fib(Bit#(32) v);
        //$display("request fib %d", v);
        frame.docall(FIBSTATE1, FIBSTATECOMPLETE, truncate(v), 0);
     endmethod
        
  
negative.code: 	   frame.doreturn();
  	end
       else
  	// call FIBSTATE1 and return to FIBSTATE2
  	// call with argument frame.args -1 and tmp2 = 0
  	frame.docall(FIBSTATE1, FIBSTATE2, frame.args - 1, 0);
       endrule
  
  