D9110MCDP MIPI C-PHY and D-PHY Protocol Trigger and Decode

D9010MCDP

MIPI C-PHY and D-PHY protocol trigger and decode software for Infiniium oscilloscopes

Product Overview

C-PHY and D-PHY are MIPI Alliance’s physical layer (PHY) standards that provide high-throughput performance over bandwidth-limited channels to connect displays and cameras to an application processor. The standards provide a PHY for the MIPI Alliance’s various Camera Serial Interface (CSI) and Display Serial Interface (DSI) specifications. This enables engineers to scale their implementations to support a wide range of higher resolution image sensors and displays, while keeping power consumption low. However, because both DPHY and C-PHY support two application layers, engineers implementing a D-PHY or C-PHY interface must be able to see a device’s signal integrity and protocol data to ensure it conforms to the MIPI specification.

MIPI serial buses are the backbone for communication in mobile products. The serial bus interface provides contentrich points for debug and test. However, since these protocols transfer bits serially, using a traditional oscilloscope has limitations. Manually converting captured 1’s and 0’s to protocol requires significant effort, can’t be done in real-time, and includes potential for human error. As well, traditional scope triggers are not sufficient for specifying protocol-level conditions.

Key Features

Protocol searching

Included in Keysight’s D9010MCDP software is a suite of configurable, protocol-level conditions for CSI-2 or DSI-2 interface buses that give engineers access to a rich set of integrated protocol-level searching capabilities. This protocol searching feature enables engineers to find and isolate error packets or specific patterns of interest from acquired data.

Protocol decode

D9010MCDP supports CSI-2 and DSI-2 protocol decode based on MIPI D-PHY and C-PHY. Perform and view decode information on both live and saved waveforms. Decode up to any combination of 4 live or saved waveforms.

The protocol list window is correlated between the waveform and selected packet on the list. The selected packet (highlighted blue row), is time-correlated with the blue line in the waveform display so that engineers can easily see the signal shape of specific packet data.

Keysight provides a unique C-PHY triggered eye diagram function for simultaneously monitoring signal quality and protocol. With this feature, engineers gain greater insight into the C-PHY signal and can better determine whether issues are due to signal quality or protocol data.

Keysight MIPI D-PHY protocol decoder software provides multilane decode up to 4 data lanes. User can select number of data lane from 2 to 4 lanes. However, due to oscilloscope’s channel limitation, multilane decode will use recovered clock instead of existing clock in D-PHY. Also, same reason, multilane decode will support only HS data decoding, not LP data.

MIPI C-PHY

Overview

C-PHY requires few connectors than D-PHY, also does not require a separate clock lane, and provides flexibility to assign individual lanes in any combination to any port on the application processor via software control. Due to similarities in basic electrical specifications, C-PHY and D-PHY can be implemented on the same device pins. 3-phase symbol encoding technology delivers approximately 2.28 bits per symbol over a three-wire group of conductors per lane. This enables higher data rates at a lower frequency, further reducing power.

Recommended connection

To achieve a higher symbol rate from the DUT, Keysight recommends connecting 3 differential active probes for single-end probing. It is also possible to probe differentially so that data can be obtained without having to configure functions. However, due to the long length between positive and negative pins on the differential active probe, the probe bandwidth may not fully cover the signal’s bandwidth range as required to see the right signal shape.

The C-PHY decoder software requires 3 differential signals for decoding C-PHY data. A single-end probed signal must therefore be changed to a differential signal for decoding. To accomplish this, use the “Subtract” function to make 3 differential signals from a 3-wire signal before starting to decode the C-PHY protocol. The required signals will be VAB(VA-VB), VBC(VB-VC) and VCA(VC-VA).