2.8.2. Viewing Data with Different Acquisition Modes
Different acquisition modes capture different amounts of data immediately after running the Signal Tap logic analyzer and before any trigger conditions occur.
Non-Segmented Buffers in Continuous Mode
In configurations with non-segmented buffers running in continuous mode, the buffer must be full of sampled data before evaluating any trigger condition. Only after the buffer is full, the Signal Tap logic analyzer starts retrieving data through the JTAG connection and evaluates the trigger condition.
If you click the Stop Analysis button, Signal Tap prevents the buffer from dumping data during the first acquisition prior to a trigger condition.
Buffers with Storage Qualification
For buffers using a storage qualification mode, the Signal Tap logic analyzer immediately evaluates all trigger conditions while writing samples into the acquisition memory. This evaluation is especially important when using any storage qualification on the data set. The logic analyzer may miss a trigger condition if it waits to capture a full buffer's worth of data before evaluating any trigger conditions.
If a trigger activates before the specified amount of pre-trigger data has occurred, the Signal Tap logic analyzer begins filling memory with post-trigger data, regardless of the amount of pre-trigger data you specify. For example, if you set the trigger position to 50% and set the logic analyzer to trigger on a processor reset, start the logic analyzer, and then power on the target system, the trigger activates. However, the logic analyzer memory contains only post-trigger data, and not any pre-trigger data, because the trigger event has higher precedence than the capture of pre-trigger data.
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