Saleae Logic User Manual page 64

introduced in a future version. In the meantime, try to keep the memory usage below the installed
RAM amount. Some systems with high-performance hard drives may be able to page RAM in real
time for some period of time after RAM is exhausted.
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Keep in mind that in order to successfully capture a signal, you must sample faster than that signal.
That is due to the nature of asynchronous sampling and is described by the Nyquist-Shannon
sampling theorem. With our products, in order to accurately sample a digital signal, you must
sample at least 4 times faster than that signal.
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To accurately record an analog signal, you must sample at least 10 times faster than that signal.
That is due to the filter response of our down-sampling filter as well as the hardware anti-aliasing
filter that defines the maximum analog bandwidth of the device.
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Captures can always be ended early. If you are watching memory usage during a capture and
decide that it's not safe to allow the capture to complete, or if you are sure that the event of interest
has already been captured, you can end the capture by pressing the Stop button.
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The software does not have an automatic trigger and re-arm feature like an oscilloscope with real-
time display. Our software requires each trace to be started manually with the Start button.
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If you are not able to record long enough for your application due to memory limits, you may want to
take a look at the socket API. Several customers have used it to automatically start, save, and
restart captures to allow much longer recordings with only small (<1 second) gaps between very
long captures.
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Some devices, including Logic Pro 8, Logic Pro 16, and the original Logic16, support multiple
selectable voltage thresholds. In addition to being required to correctly record digital data at different
IO threshold standards, voltage thresholds are important for rejecting noise near ground and
avoiding double edge hits.
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You may be recording at too slow of a digital sample rate or using the wrong voltage standard if you
find one or more pulses in the digital data that are only 1 sample wide (1/sample rate). In these
cases, you may want to review your sample rate settings, review this guide, or contact support.
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