Protocol Trigger and Decode

“Protocol Trigger and Decode” explores the advanced capabilities and benefits of protocol triggers and decodes, a feature available on the next-generation Infiniium EXR, MXR, and UXR-series oscilloscopes. This feature is essential for engineers working with serial buses and conducting protocol tests.

The video begins by highlighting the historical challenges engineers faced when analyzing serial buses on oscilloscopes. Previously, engineers had to manually save or print out packets and count the bits to understand the data. This method was time-consuming and prone to errors. However, with Keysight oscilloscopes, this process is now automated. These oscilloscopes can trigger on and decode dozens of serial protocols, significantly saving time and reducing errors.

Setting up protocol triggers and decodes is straightforward. Once the bus of interest is probed, users can enter the “Analyze - Protocol Decode” menu. Here, they specify the bus they are working with, such as a standard CAN signal, and define data sources, bus speeds, and other basic information. By pressing “Auto Set Up,” the oscilloscope initiates the decoding process and sets a basic trigger at the beginning of each packet.

The trigger menu allows users to further refine what data on the bus they want the oscilloscope to digitize and display. The type drop-down menu lists all relevant types of transmissions or packets available for the specific bus. Users can define up to three fields, which are parameters of the bus as defined by its specifications. For example, with CAN, users can define the packet identifier or data length code, among other parameters.

In the video, the oscilloscope is set to trigger on all CAN error frames and begin a segmented memory capture, showing 100 consecutive errors on the CAN bus. Users can click through each error to see further details in the results pane, which includes a picture of the header, payload, and a list of details. Additionally, the time-aligned view is displayed right below the signal itself.

Overall, the lesson offering insights into the practical applications and benefits of protocol triggers and decodes in modern oscilloscopes. It aims to empower users with the knowledge to leverage these advanced tools for optimal serial bus analysis and protocol testing.