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15 March 2021

The Important Difference Between ProtoSync™ and CrossSync™ PHY

Figure 1: CrossSync PHY captures everything from
physical through protocol layers at once.
With the recent release of our new CrossSync™ PHY for PCI Express® product, some of you may be wondering how it’s any different than ProtoSync™ for PCIe®, which has been around for quite a few years.

ProtoSync is an option for Teledyne LeCroy oscilloscopes with bandwidths that support high-speed serial data analysis. We’ve released ProtoSync options for PCIe, USB, SAS/SATA and Fibre Channel. ProtoSync links the same Protocol Analysis Suite software that is used with our protocol analyzers to the oscilloscope application, so that you can see physical layer decodings in the familiar PETracer and BITracer views right next to the decoded analog waveform. 

CrossSync PHY differs from ProtoSync in the three, significant ways:

1. Trigger. ProtoSync does not provide any triggers. What you see is an oscilloscope acquisition that was triggered from the oscilloscope in the traditional way. CrossSync PHY actually triggers both an oscilloscope and a protocol analyzer simultaneously. In fact, it is the protocol analyzer that initiates the trigger, as done with our other CrossSync products designed to cross-trigger different protocol analyzers. That means that the trigger can be a higher-level protocol event, instead of a lower-level physical layer or link layer event, as is generally the best case with our oscilloscope serial triggers.

2. Acquisition. ProtoSync only gives you another way of looking at an oscilloscope acquisition. You would have to make a separate acquisition with a protocol analyzer to see what is happening at the protocol layer. Through the use of an interposer, CrossSync PHY triggers two instruments at once, and two full acquisitions are made. The interposer enables observation of both electrical and protocol behavior without disturbing the link. Sideband signals, reference clock and power rails are all easily accessible to oscilloscope probes. Because they were triggered together, the acquisitions are fully synchronous—a time-correlated picture of everything that happens from the electrical through the protocol layers. You can easily measure timing relationships between protocol and electrical domains, observe electrical-level results of protocol-level commands, and get cross-layer insight into link training behavior simply not available by any other means.

3. Navigation. The CrossSync PHY Control Panel actually integrates the two applications into one, and you can navigate both acquisitions in sync using the new Navigation Bar or Packet Zoom features. Therefore, you need never lose the time-correlation between the physical and protocol layer data. While ProtoSync shows you the protocol analyzer view next to the physical layer decoding, there is less coordination between the two windows.

CrossSync PHY is supported on all WaveMasters, LabMasters and the Summit T54 Protocol Analyzer, with the addition of the PCI Express 4.0 x4 M.2 M-Key Interposer and DH Series High-bandwidth Differential Probes (if you wish to acquire high-speed data lanes). 

For a more in-depth look at CrossSync PHY, watch the on-demand webinar, “Debug PCIe Faster with Cross-layer Analysis Tools.”

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