Open Core Protocol (OCP) flexibility, configurability and scalability are the key elements making OCP massively used and successful into major electronics markets. Upon these characteristics any IP can adopt the best interface for the connection to the OCP backbone with immediate benefit for bandwidth capability. This has made OCP broadly used in many applications like multimedia, telecom and gaming.

In these consumer market domains, time-to-market the key success factor for products; as a consequence a straightforward and silicon proven verification process aiming at first-time-working SoC becomes mandatory to win over competitors and to avoid silicon re-spins.

<>In contrast to other protocols, the OCP characteristics offer to system architects an unprecedented added value that must be coupled with powerful and silicon-proven verification techniques like the usage of mature VIP for the validation of functionality of the SoC with OCP on board. On the other hand, the substantial impossibility to define an OCP conformance test exposes SoC to functional risks, a serious worry for system designers.

However, any risk is drastically reduced when a solid and comprehensive VIP Qualification Process (QP) is available, because this will ensure best-in-class quality level, a measure of reliability, then robustness.

The ideal scenario
The ideal scenario of achieving an exhaustive OCP VIP Qualification Process is a dramatic challenge since the number of the allowed profiles, interface configurations and any combination of them make practically not viable to set up a QP according to such approach: the massive cost for the high multiplicity and the undetermined level of reliability, a consequence of the lack of a OCP ISO conformance test.

The Qualification Process (QP) for OCP VIP implemented by Yogitech Verification Team has been setup with a rigorous heuristic approach, and it is a distilled format of the long lasting experience of product support, with many OCP-based designs having ended on silicon.

It is based on a methodology capable to extend the OCP-IP consortium official checks, coverage items and standard configurations with a larger number of profiles, filtered with a systematic methodology and robust metrics.

The QP selective regression test suite is shaped in such a way to get unprecedented level of cross-coverage over both the whole set of profiles and features. This approach increases OCP VIP quality and robustness to the highest level, allowing the final users to trust the verification process, whatever profile or configuration they have chosen to use.

Stepping down into details of the qualification process, it is necessary to remind that OCP offers two degrees of freedom in profiling interfaces: one dimension is the signals list; the other one accommodates the features list. Following this conceptual schematization of the standard we can describe any profile master as a two-dimensional table where axes are the signals and the features, respectively.

Figure 1: A table master is a matrix able to accommodate signals and features for each ocp profile, highlighting forbidden combinations.

The table master in Figure 1 above includes blackened cells to represent the forbidden combinations of signals and features.

An actual profile is described by a table where it is possible to characterise different scenarios by simply checking the white cells of the enabled feature or the connected signal. By overlapping all the tables, filtering all the white cells with at least a check mark, all the features and all the corresponding signals have been applied at least once.

Even though this is not an exhaustive method, it is a straightforward way to create a comprehensive and distilled set of the many configurations of practical use. Then, this mapping process facilitates detecting if gaps are still present, either in the features list or in the signals list.

Figure 2: OCP space results from the overlap of individual profiles where tested combinations are checked out.

As shown in Figure 2 above, one can keep on accumulating scenarios for a complete coverage of all the cells. Process can be extended until each of the cell has been checked a pre-defined number of times, the higher the number, the most the qualification process can be rated in terms of robustness.