interface IAsync {
  in void e();
  in void c();
  out void cb1();
  out void cb2();

  behaviour {
    bool idle = true;
    [idle] {
      on e: { cb1; idle = false; }
      on c: {}
    }
    [!idle] {
      on e: illegal;
      on c: idle = true;
      on inevitable: { cb2; idle = true; }
    }
  }
}

component async_synccb {
  provides IAsync p;
  behaviour {
    requires dzn.async i;
    bool idle = true;
    [idle] {
      on p.e(): { i.req(); p.cb1(); idle = false; }
      on p.c(): i.clr();
    }
    [!idle] {
      on p.e: illegal;
      on p.c(): { i.clr(); idle = true; }
      on i.ack(): { p.cb2(); idle = true; }
    }
  }
}