Sizing Up eUSB2 Verification

USB is one of the most widely used interfaces in the PC market for more than 20 years. Though it remains the same form in laptops and servers, it never stops its evolution in terms of capacity and speed. Embedded USB2.0, known as eUSB2, was created to address the concerns of power efficiency and portability. Although eUSB2 largely reuses USB2.0 protocol layer, the verification of eUSB2 can be never thought of as a miniature of USB2. The challenges of eUSB2 verification are significant, due to its brand new PHY layer and compatibility requirement with USB2 devices.

eUSB2 has 2 working modes, namely native and repeater mode: Native mode is for inter-chip connection between standalone eUSB2 devices, and repeater mode is employed when eUSB2 device must exchange data with USB2 port or extend to a  longer transmission distance. eUSB2 also distinguishes itself with device and host like USB2. With these requirements, several topologies could be introduced into eUSB2 related SoC or IP verification, in which DV engineers need to build a set of solid environments to cover all eUSB2 function aspects. The complexity comes not only from these different topologies, but the stimuli generation, protocol and timing checking, error injection, and debugability as well.

Cadence eUSB2 VIP was created to overcome the verification challenge. eUSB2 VIP natively supports all types of transfers, enumeration, reset signaling, transaction, and packet checkers. Verification engineers can easily create numerous sophisticated scenarios without focusing on creating BFM (bus functional model) or caring too much about low-level PHY control logic. As an example to demonstrate eUSB2 VIP capacity, let's have quick look at how it helps in different topologies which eUSB2-related IP or SoC involves.

• Native mode: Host VIP + Device DUT and Host DUT + Device VIP. In this case, VIP is the link partner to the design, and it either generates the traffic or responds to the commands.

• Repeater mode: Host VIP + Repeater DUT + Device VIP. Noted in this case, eUSB2 host talks to USB2 device through DUT repeater, with which USB2 host can also communicate with eUSB2 device.

• VIP can work as a stacked model for host repeater mode and peripheral repeater mode. Here below it shows the host repeater mode.

There could be other different topologies in an SoC, while adopting eUSB2 VIP is the best way to keep verification efficient and productive. Once the topology environment is set up and basic tests are exercised, users may perform more advanced testing, like scoreboard, stimulated reset and wakeup, mimicking device disconnect, packet corruption, and even more towards full functional compliance to the specification. However, these details are beyond the scope of this blog, and we will introduce them in our future blogs.

If you are interested in eUSB2 VIP or wish to know about VIP, please reach out to your local Cadence representative, and you may send an Email to support@cadence.com, we will be glad to assist you.