Sequence item overriding is not working(set_type_override)

[dave_345]

I have a UVM agent which acts as a MASTER and generates transactions for a protocol. Command and data transactions are transferred on same data bus with command/ data select line. Command transaction have a HEADER format.I want to extend this agent for different type of HEADER FORMATS. agent does header packing in driver.

For that i created a new sequence item extended from base sequence item, and did set type override in test case. as existing sequence take base sequence item as argument. i have created new sequence for new HEADER. but although i did set_type_override sequencer dosen't accept new type of item and gives error for new field inside extended driver. how can i solve this??

[lisakb1963]

This should work, but it may be something odd in your base class. I would look at protocol layering. This is very useful for OSCI or other protocols that have a high data layer over a physical data layer:

TCP-IP

USB 3.0

PCIe

It involves using TLM 1.0, and reconstruction of data -- but it is useful. From what you describe, you aren't doing anything this complicated -- but this may be the way to solve your problem. This is described in the UVM User's Guide 6.5.2. It is also a usage model for UVM_REG (there are three) --- but unless you really have abstracted registers to the hardware -- you can't do anything like grab, lock, priority, ISR. But it is extremely useful for Layering of of data protocols.

[uwes]

this sounds like as if you are having a base class handle pointing to a derived class. so even if the handle references a derived class object you can only access base class properties. in order to access the properties of the derived class you have to $cast the object to the derived type.

btw it would be good if you show more of your code and the full error message if you want more help than guessing.

/uwe