Clocking Blocks and Modports in UVM interfaces

[petermonsson]

Hi all,

What is the UVM opinion of using clocking blocks and modports in the interface of a UVC? The integrated examples are split with the UBUS and VIP components saying No while the APB component says yes.

Best Regards

Peter

[dave_59]

A big problem with modports and virtual interfaces is that some simulators have failed to implement all the required checks (only read modport input variables, etc.), removing much of their value to the user. It may be that the LRM failed to clearly explain their intent.

Clocking blocks also suffered from poor specification in the LRM and were only recently cleared up in the 1800-2009 LRM. I do find the useful for interacting with wires inside interface.

Although designed to remove race conditions, they can introduce other race conditions especially if you mix the clocking block event with other events in the same interface. I just wrote a paper mentioning this issue at last week's DVCon.

[petermonsson]

Hi Dave,

Thanks. I wasn't aware of all those issues.

Best Regards

Peter

[arno]

Hi Dave,

as of now, the virtual interface is the most adopted way of connecting the tb and dut, hard to avoid.

Putting the abstract class on the side, what would your advice be on using clocking-blocks/modports versus NOT using them ?

Some commercial VIPs use them, and I'd like to have your advice on this.

Thanks,

Arno