Shorthand macros with user defined implementation
Posted by Vidyashankar Ramaswamy on February 3rd, 2010
The transaction class objects are created by extending the base class vmm_data. Vmm_data class has many virtual methods which need to be implemented by the extended class. This can become a laborious process as this is done for each extended class object. However, a set of shorthand macros available to help minimize the amount of code required to create these data class extensions. These shorthand macros can be used on per data member basis which provides a default implementation of all the require methods. Following is an example.
| . . . 1 class apb_trans extends vmm_data; 2 `vmm_typename(apb_trans) 3 rand enum {READ, WRITE} kind; 6 `vmm_data_member_begin(apb_trans) |
The class properties are declared as shown in Line number 3 to 5. Line number 6 and 10 marks the start and end of the shorthand macro section. Based on the variable type , the appropriate macros are called (line number 7 to 9). As the name says “DO_ALL” means use this variable in all the virtual method implementations. Say if you want to exclude the “kind” property from printing, then you can use “DO_ALL – DO_PRINT”. Please refer to the VMM user guide for more details on this.
User defined implementation
Shorthand macros provide the default implementation for all the vmm_data virtual methods. If you want to override the default implementation of a method, then you have to implement the do_* method. For example say you want to change the implementation for byte_size, You can still use shorthand macros but need to explicitly implement the apb_trans::do_byte_size() method and force VMM not to provide the default implementation. The example code is shown below.
| 1 virtual function int unsigned do_byte_size (int kind = –1) ; 2 . . . 3 . . . 4 endfunction |
Constructor replacement
In some cases a transaction class might need a custom constructor with different arguments. Please note that the explicit constructor implementation is done using the shorthand macro `vmm_data_new() as shown below (line 1). The new implementation should follow the macro definition (Line number 2 to 5). It is also important to provide default values for the arguments to make the transaction class factory-enabled (Line number 2).
| 1 `vmm_data_new(apb_trans) 2 function new (vmm_log log=null, vmm_object parent=null, string name=””); 3 super.new(. . ., . . .) ; 4 . . . 5 endfunction |
The shorthand macros are also available for messaging service (vmm_log), vmm_unit configuration, RTL configuration (vmm_rtl_config) and TLM ports. For the complete list, please refer to the VMM user guide.
