Deep memory: history and segmented memory optionFollow article
What is your challenge?
Embedded designs are an integral part of today’s electronic systems comprising analog signals as well as signals from serial and parallel buses. When debugging such designs, a common challenge is to simultaneously capture enough content of both slow and fast signals with sufficient resolution between the sample points to zoom in and see signal details.
Besides, when analyzing the spectrum of a signal, the ability to look at longer periods of time is essential, because the frequency resolution depends on the amount of time that is available for analysis. More time means finer resolution.
High resolution, and therefore deep memory, is vital when trying to view fast and slow signals at the same time and correlate the signal content. Sample rate is another important characteristic for signal analysis. The higher the sample rate, the higher the maximum frequency that users can view. This ensures that no important signal details are missed, e.g. glitches spikes or other anomalies that can cause a malfunction of the design.
An oscilloscope with deep memory solves the described problem. Oscilloscopes from Rohde & Schwarz traditionally offer high memory depth as a standard. The different memory upgrade options offer an even greater advantage since users can capture an incremental number of segments at a specific depth. The table gives an overview of R&S solutions.
What about segmented memory?
Segmented memory limits the acquisition to relevant signal elements. During signal acquisition with segmented memory, the available memory is divided into smaller segments, each with a defined number of samples. The user defines the length of the segments based on the relevant parts of the signal, e.g. the packet length of a protocol-based message.
At the trigger point, the data of interest is stored in memory along with the trigger timestamp. Time periods without interesting activity are not acquired. As a result, users optimize utilization of the memory, fast sample rates can be maintained and much more relevant data than with single-shot acquisition can be recorded.
Segmented mode is particularly useful for capturing bursts of activity surrounded by long periods of dead time. Many serial buses and communications signals fit into this category.
Single shot versus segmented acquisition
What is Rohde & Schwarz history mode?
The history mode offers substantially deeper memory on embedded oscilloscopes. In history mode, a highly precise trigger timestamp permits precise time correlation of signal events. Users can scroll through past acquisitions and analyze the data using all oscilloscope tools, e.g. protocol decode and logic channels. Individually marked segments can be selected in the acquisition table for display. Alternatively, the history function can be used to automatically playback all segments.
The following table provides a competitive comparison. It turns out that oscilloscopes from Rohde & Schwarz often offer more memory than comparable instruments, which is why those instruments are ideal when debugging embedded designs.