Pre-Trigger Sweeps - HBM Genesis GEN5i User Manual

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Figure 9.4: Ring buffer operation of memory
The physical memory therefore forms a ring buffer, into which information can
be continuously added (Figure 9.4). This process of filling the ring buffer
memory terminates only when the recording logic indicates that the recording
must be ended. Once the recording has stopped, the content of the buffer
memory becomes available to the control PC for processing. This is also called
circular recording.

Pre-trigger sweeps

As we have seen, data emerging from the ADC is stored in the buffer memory.
When recording, the memory is continuously refreshed with new sample
values, until storage is halted. The information available in the memory is a
history of the recorded signal up to the moment of 'end-of-recording'. The
extent of this history depends on the sample rate and the data storage capacity
(length) of the memory. If we assume a memory length of 40 000 samples and
a sample rate of 10 000 samples per second, then the time window of the
history will be:
Storage into the ring buffer can be stopped only by a 'stop' signal from the
recorder. This signal is called the "trigger". For full details on triggering see
chapter "Digital Trigger Modes" on page 122.
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