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propagating data when generating VE

yongchen

Hi,

I was confused when progapating data to generate VE by using "connect_pointers()" and "keep upper.comp = read_only(comp)".

1) When should I use "connect_pointers" and when should I use "keep ... read_only"? For example, xserial example from Incisive gives an example as this:

extend ACTIVE has_tx_path xserial_agent_u {

   tx_bfm: xserial_bfm_u is instance;

      keep tx_bfm.driver == read_only(tx_driver);

      .....

      connect_pointers() is also {

          tx_bfm.agent = me;

      };

}

 

2) In document from Invisiv 11.1, "Specman IntelliGen User Guide", 3-9, there is an example to show connect_pointers() as:

extend agent {

   bfm: ex_atm_bfm is instance;

  driver: ex_atm_sequence_driver is instance;

  connect_pointers() is also {

    bfm.driver = driver;

    driver.bfm = bfm;

  }

};

My question is : why there is no "!" before driver/bfm? In what case should I add this "!" to unit?

 

thanks

 

  • Hello Yongchen.

    In general you would use constraints to connect unit pointers. The connect_pointers() method is provided so that you can avoid deep hierarchical constraints when hooking up TLM ports, monitors to scoreboards etc. For example your bus monitor might have a pointer to a scoreboard "!p_scbd : my_scoreboard". You can then hook that procedurally via connect_pointers() from the top-level: "tb_top.axi_env.monitor = tb_top.scbd". Sometimes it's just easier this way than using constriants. There's no hard rule, so it's up to you to judge what is best.

    You would use the "!" (do-not-generate) attribute on a unit if it's meant to serve as a pointer and will be connected procedurally via connect_pointers(). Without the "!" a unit declaration MUST be either declared "is instance" or constrained to point to a real instance via a keep constraint. The "is instance" tells the generator that this object is a real unit, not a pointer to a unit.

    Hope this helps.

    Steve. 

  • Thanks Steve. It is very helpful.

    Yong Chen 

     

     

     

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