How to "Layer" Measurement Tools

Figure 1: Multi-grid display "layers" multiple
measurement tools to find hidden glitch.

Teledyne LeCroy oscilloscopes have four, distinct sets of measurement tools, including measurement graticules, cursors, parameters and graphs. These tools developed historically and are designed to be “layered” on multi-grid MAUI® oscilloscopes so that each addition brings a new level of understanding and insight. Even on oscilloscopes that do not have multi-grid displays, as shown here, several measurement tools can be applied at once for added insight. Read on to see how, properly combined, they can help you find waveform anomalies and assess their frequency of occurrence in a few, simple steps.

TDME Primer: Automated Timing Measurements of USB-C Protocols

Figure 1: Interleaved decoding of USB-PD and DP-AUX signals.

Increasingly, serial data analysis is analysis of the interoperability of the many protocols that must perform together within interconnects and embedded systems. Nowhere is this more true than for USB-C® devices, which we’ll focus on in this post, although these examples of cross-protocol timing measurements could apply to any two protocols supported by our TDME and DME options.

The USB-C connector packs many protocols onto one, small pin set, and maintaining signal and power integrity is a compliance challenge. Besides high-speed data delivery, USB-PD (power delivery) provides flexible power distribution, while auxiliary sideband signals, like DisplayPort™, transport video. Troubleshooting these capabilities requires the ability to measure timing between serial data packets, as well as between data packets and analog signals. 

For example, DisplayPort over USB-C (DPoC) in alternate mode (alt-mode) can manifest as an interoperability failure if there is a timing issue between alt-mode initiation and the start of DP-AUX.

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:

TDME Primer: Serial Trigger and Sequence Mode Sampling

Figure 1: Sequence mode sampling packs multiple acquisitions
into memory with very little “dead time” between them.

Sequence mode sampling, also referred to as segmented acquisition, is a sampling mode that divides the oscilloscope’s acquisition memory into a user-defined number of equal length segments. Each segment stores a single acquisition of the triggering event, with as much buffer zone as will fit into that segment, given the total number of segments requested. Only after all segments have been acquired is the data processed and displayed. 

The real power of sequence mode becomes evident when you combine it with intelligent triggers, such as the serial data triggers delivered with TDME options. 

TDME Primer: Selecting Sample Rate for Serial Bus Analysis

Figure 1. Sample rate of only four sample points per bit
decodes correctly and lengthens serial bus acquisition.

Teledyne LeCroy supports trigger, decode, measure/graph, and eye diagram (TDME) software options for over 20 serial data standards, and the list is growing. This series will address practical tips for using TDME software successfully, and showcase some examples of applying TDME capabilities to real-world problems.

Given the wide range of protocols supported, you might be curious about how to best choose the oscilloscope sampling rate for a given standard when acquiring serial data signals. The optimal sample rate is determined by three principal factors: 

1) the bandwidth of the signal being digitized by the oscilloscope’s analog-to-digital converter (ADC);

2) the desired duration of the acquisition;

3) what you are going to do with the acquisition.