Intel® Quartus® Prime Pro Edition User Guide: Debug Tools

ID 683819
Date 7/08/2022
Public

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2.4.8. Filtering Relevant Samples

The Storage Qualifier feature allows you to filter out individual samples not relevant to debugging your design.

The Signal Tap logic analyzer offers a snapshot in time of the data that the acquisition buffers store. By default, the Signal Tap logic analyzer writes into acquisition memory with data samples on every clock cycle. With a non-segmented buffer, there is one data window that represents a comprehensive snapshot of the data stream. Conversely, segmented buffers use several smaller sampling windows spread out over more time, with each sampling window representing a contiguous data set.

With analysis using acquisition buffers you can capture most functional errors in a chosen signal set, provided adequate trigger conditions and a generous sample depth for the acquisition. However, each data window can have a considerable amount of unnecessary data; for example, long periods of idle signals between data bursts. The default behavior in the Signal Tap logic analyzer doesn't discard the redundant sample bits.

The Storage Qualifier feature allows you to establish a condition that acts as a write enable to the buffer during each clock cycle of data acquisition, thus allowing a more efficient use of acquisition memory over a longer period of analysis.

Because you can create a discontinuity between any two samples in the buffer, the Storage Qualifier feature is equivalent to creating a custom segmented buffer in which the number and size of segment boundaries are adjustable.

Note: You can only use the Storage Qualifier feature with a non-segmented buffer. The IP Catalog flow only supports the Input Port mode for the Storage Qualifier feature.
Figure 62. Data Acquisition Using Different Modes of Controlling the Acquisition Buffer

Notes to figure:

  1. Non-segmented buffers capture a fixed sample window of contiguous data.
  2. Segmented buffers divide the buffer into fixed sized segments, with each segment having an equal sample depth.
  3. Storage Qualifier allows you to define a custom sampling window for each segment you create with a qualifying condition, thus potentially allowing a larger time scale of coverage.

There are six storage qualifier types available under the Storage Qualifier feature:

  • Continuous (default) Turns the Storage Qualifier off.
  • Input port
  • Transitional
  • Conditional
  • Start/Stop
  • State-based
Figure 63. Storage Qualifier Settings

Upon the start of an acquisition, the Signal Tap logic analyzer examines each clock cycle and writes the data into the buffer based upon the storage qualifier type and condition. Acquisition stops when a defined set of trigger conditions occur.

The Signal Tap logic analyzer evaluates trigger conditions independently of storage qualifier conditions.

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