New MIPI Standards, Part 2: UniPro

In an earlier post, we discussed M-PHY, which is poised to become the flagship PHY interconnect between components inside mobile devices. One of the key protocols that will run over M-PHY is UniPro. UniPro has a lot of potential in its own right, and is already being referenced by JEDEC for use in its new Universal Flash Storage (UFS) specification. Below, we’ve outlined some interesting test features built-in to UniPro that will allow full testing of the M-PHY interface.

Testing the M-PHY Interface
UniPro implements a test packet that will force a device into a special test mode, thus the test mode can be enabled in band. You only need access to the UniPro interface to enable the test mode. That functionality, in itself, is not new; the SATA specification has done something similar with its Built-In Self Test (BIST) packet.

The UniPro test mode, however, is unique - it was designed to be easily enabled using PHY test gear that is typically not protocol aware.

If you think of the common tools used for sending signaling to a device during PHY testing (signal generators, pattern generators and waveform generators), they are not protocol aware, and they are not ‘dynamic’ in that they can’t respond to incoming stimulus from the device under test. This means that using these tools to enable test modes in band can be difficult because you are trying to get them to mimic complicated protocol behavior that they simply weren’t designed for.

In the UniPro case, the test mode can be enabled during the initialization period. This mechanism is crucial because if that test mode packet is received while the device is initializing, the device will skip the handshaking required in the normal initialization, and go directly into test mode. This feature is important because it allows PHY test equipment (that is not protocol aware) to be used to put a UniPro product into test mode easily, meaning you can test this interface faster using less equipment.

David Woolf, Research and Development