SDAIII and QualiPHY Software: Oscilloscope Eye Diagrams for Compliance and Debug

Figure 1. SDAIII enables eye diagrams and eye
measurements of four lanes of  streaming data.

Besides the serial TDME and TDMP options discussed earlier, there are other ways to generate eye diagrams on your Teledyne LeCroy oscilloscope for compliance testing and debug.

SDAIII Serial Data Analysis Software

SDAIII offers the most comprehensive eye diagram capabilities for Teledyne LeCroy oscilloscopes, with tools for optimizing the displayed eye that are especially useful to high-speed serial data analysis.

Serial Trigger, Decode, Measure/Graph & Eye Diagram (TDME) Software: Oscilloscope Eye Diagrams for Debug

Figure 1. Two eye diagrams generated from 
three active USB serial decoders.
Click any image to enlarge it.

The eye diagram is a general-purpose tool for analyzing the signal integrity of serial digital communications signals. It shows the effects of additive vertical noise, horizontal jitter, duty cycle distortion, inter-symbol interference, and crosstalk on a serial data stream. The vertical opening of the eye is affected by these elements, as well as gain differences between devices on the bus, so that the more problems with signal integrity, the more “sleepy” the eye appears. A wide open eye is indicative of good signal integrity.

It is commonplace to use an oscilloscope with decoder software to analyze the health of serial data streams, where the combination of the electrical waveform and the link layer decoding shows if and where the protocol breaks down at the physical layer, but an eye diagram can better show the degree of signal interference that may be impacting the serial logic—especially if it could be generated for particular devices or packets.

Debugging Ethernet, SATA, and PCIe for IoT Devices

Figure 1: A generic IoT block diagram
shows serial-data links in blue

In our ongoing review of debugging serial-data standards for Internet of Things (IoT) devices, let's now turn to three more popular protocols: Ethernet, SATA, and PCIe. Ethernet is found in computer networking applications, while the Serial Advanced Technology Attachment (SATA) connects host bus adapters to mass-storage devices. The Peripheral Component Interconnect Express (PCI Express or PCIe) handles communication between root complexes (motherboards) and expansion-card interfaces.

Getting The Most Out Of Your Oscilloscope: Physical-Layer Tools

Figure 1: Trigger dialog boxes will
match the protocol of interest

Debugging and validation of the physical layer of serial-data links is a preeminent oscilloscope application area these days. Today's real-time digital oscilloscopes have a wealth of tools to help you dig into any/all serial protocols and learn what's really going on electrically with your serial links.