AT AT-LA500, Руководство пользователя

Страница: 7 / 98

AT-LA500 – U
SER MANUAL
I
NTRODUCTION
R
ELEASE
3.4 – JUNE 2009 7
Introduction
Overview
AT-LA is an instrument able to acquire digital data through 36 channels, divided in 4 banks of 9
channels each and to visualize their time behavior thanks to the dedicated software.
AT-LA is available in different configurations, depending on the maximum available memory
(varying from 2M to 4M samples).
AT-LA is connected to the system under test by means of probes with different electrical
characteristics, depending on the signals to be acquired. Each probe supports 18 channels, divided
in two banks of 9 channels each. Each probe is hot pluggable and is automatically recognized. Four
independent and programmable thresholds are available (one for each bank of 9 channels) and used
by active probes to discriminate between low and high levels.
Data acquisition starts when a triggering event is detected by the instrument. The trigger can be
configured by the user by selecting the suitable conditions on signal edges or on the input signal
levels. Furthermore, it is possible to generate internally a trigger event so that data acquisition is
independent of applied signals and it is performed automatically (free acquisition) or enabled by the
user (manual acquisition).
AT-LA can also trigger on events occurring on many serial protocols (i.e. I
2
C, SPI, RS232) and
then analyze the packets of data transferred.
Once data acquisition is terminated, data are transferred to the PC through a USB 2.0 or a USB 1.1
connection and then visualized as waveforms or values.
AT-LA can sample input signals by using an internal clock signal (Time Analysis), whose
frequency can be reduced on the basis of the signal to be acquired, or it can synchronize signal
sampling to a signal clock provided by the system under test (State Analysis).
Operating principles
Digital signals acquisition means: i) to sample input signals, ii) to convert this values in logic values
(0 and 1), iii) to organize these values in a set of waveforms.
To establish the logic value of a sampled signal, it is necessary to compare the input value to a
reference voltage, called threshold, that can assume a fixed value or can be varied depending on the
used probe. If the input value is greater then the threshold, it will be converted to a high logic state
(1), otherwise it will be converted to a low logic state (0).