A key advantage HAPS DTD offers by having visibility of many thousand signals is that more debugging is possible from a single prototyping system implementation. It means that fewer iterations might be required in order to complete the debug or validation cycles by reducing the need to switch otherwise limited signal visibility to other areas of the device under test (DUT). With iteration times of high-capacity prototyping platforms still taking many hours, it might mean that limited debugging is possible on a daily basis before needing to re-spin the implementation with revised debug signals sets. In any case, limited signal visibility is one of the reasons physical prototyping has mainly only been deployed when the RTL is in a near stable and where visibility is only required on key buses and signals.
Another interesting situation is when it might have taken many days for a specific complex trigger to “fire” only to discover that visibility wasn’t selected on necessary signals. This is where HAPS Global Signal Visibility (GSV) helps open up new frontiers for physical prototyping by enabling a “snap-shot” view of the full system state.
HAPS GSV is a recent enhancement to the debug capabilities of the HAPS physical prototyping solution that allows the state of registered instances (full system state) to be captured from the DUT without the need for pre-defined debug probe selection. As with HAPS DTD, there are a number of ways in which GSV can be set-up and deployed to help debug different scenarios but perhaps one of the most interesting is through the control the DUT clocks (Synchronous GSV) to hold parts, or even the complete DUT in a static state whilst capturing the registered instance values. In this case, the user can decide which of the DUT clocks they want to control and under what circumstances they want to control, which can be through a command issued from the Host PC or for finer control, by using the trigger from the HAPS DTD logic. Once the full system state has been captured, the controlled clocks can then be released to resume normal platform operation, or stepped by a user defined number of cycles before capturing the full state once again. This same process can then be repeated any number of times, even 10s of thousands of times, to collect the full system state of the DUT over a useful period of time. As with the HAPS DTD flow, the system state can then be downloaded and written into VCD file or FSDB database for further debugging in the chosen off-line debug environment.
Again, the use of FSDB files in the Verdi environment allows for extended debug opportunities and in the case of GSV, the use of the Siloti Data Expansion capability can expand the signal visibility to any combinatorial point between the registered instance values as collected from the HAPS physical prototyping system.