Teledyne LeCroy PXD Series - Manual (Page 29)

Operation
901217-01 ISSUED: March 2003
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INTRODUCTION
This section provides information about the standard acquisition, triggering, and measurement
features of the PXD Series Digitizer. LeCroy PXD digitizers are IVI compliant which means that the
structure of commands for setting up, capturing, and reading out waveforms follows the structure
defined in Section 4 of the IVI Foundation specification (www.IVIfoundation.org). It is recom-
mended that you review this section prior to programming the PXD modules. Detailed descriptions
of LeCroy commands are included in the Driver Help file.
ACQUISITION MODES
The Digitizer has three modes of operation: NORMAL, RIS (Random Interleaved Sampling), and
Sequence. These are defined as follows:
Normal
In Normal mode, the Digitizer will input the signals during a specified time window and create a
data array with the digitized data, which can be read out by the controller. The user programs the
number of points as well as the time window to be digitized on repetitive signals. LeCroy PXD Dig-
itizers come with 256 kpoints of memory as standard. For storing longer single-shot signals, opti-
mal memory of 4 Mpoints or 8 Mpoints/channel can be added. The maximum sample rate is 2 GS/
s, and will vary depending on the specific model and the time window setting.
RIS – For Higher Sample Rates
RIS (Random Interleaved Sampling) is an acquisition technique that allows effective sampling
rates higher than the maximum single-shot sampling rate. It is used on repetitive waveforms with a
stable trigger. The maximum effective Digitizer sampling rate of 50 GS/s can be achieved with RIS
by making 100 single-shot acquisitions at 500 MS/s. The bins thus acquired are positioned
approximately 20 ps apart. The process of acquiring these bins and satisfying the time constraint
is a random one. The relative time between ADC sampling instants and the event trigger provides
the necessary variation, measured by the timebase to 5 ps resolution.
The Digitizer requires multiple triggers to complete an acquisition. The number depends on the
sample rate: the higher the sample rate, the more triggers are required. It then interleaves these
segments to provide a waveform that is up to 50x faster than the single-shot sampling rate. How-
ever, the real-time interval over which the Digitizer collects the waveform data is much longer, and
depends on the trigger rate and the amount of interleaving required. The digitizer is capable of
acquiring approximately 40,000 RIS acquisitions per second.