// example 9

<'
type bus_state_t : [busy, idle, waiting, error];

struct bus {
   // These are the interface or 'public' methods and fields. They are not prefixed 
   // with anything since 'public' access level is the default

   reset()@clk_sys is { // "reset" can be called from other structs like the data driver or the CPU model.  

      'reset_bus' = '0'; // drive '0' to the reset pin 'reset bus'
      
      wait 3*cycle; // wait 3 'clk_sys' cycles for reset to finish
      
      state = idle; 
      // "state" is a private struct member (see below). Therefore other users can not access it directly.
   };
   
   bus_state_t get_state() is {     
      //To get the current state, users from other structs must call "get_state()" since state is private
      // and they can not access it directly.

      return state;

   };

   send_data (l: list of bit)@clk_sys is { 
      // send data calls some private TCMs that take care of actually  sending the data.

      if check_data(l) {
         signal_data_start();
         drive_data(l);
         signal_data_end();
      };
   };
   
   // Below are the private methods and fields. Nobody is supposed to use them except the owner of the struct.

   private state : bus_state_t;     
   // other structs can change "state" or see its value only through "reset()" or "get_bus_state()"
   keep state == idle;

   // All the methods below are hidden from other users. They can not use them or they will get a compilation error.

   private bool check_data (l: list of bit) is {
   //...
   };
   
   private signal_data_start () is {
   //...
   };

   private drive_data (l: list of bit) is {
      //...
   };

   private signal_data_end (l: list of bit) is {
      //...
   };
};
'>