AT AT-LA500, Руководство пользователя

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AT-LA500 – U
SER MANUAL
R
ELEASE
3.4 – JUNE 2009 30
•
Trigger when EQUAL:
The trigger event occurs when the state of the evaluated
signals is equal to the specified pattern;
•
Trigger when NOT EQUAL:
The trigger event occurs when the state of the evaluated
signals is different from the specified pattern;
•
Trigger when CHANGED:
The signals selected for a trigger event on logic levels are
examined when data acquisition starts. These sampled values
will constitute the reference pattern. The trigger event occurs
when the state of the selected signals is different from the
reference pattern.
The conditions chosen by the user on logic levels are ignored.
AT-LA500 will simply use the information related to which
channels are to be examined for trigger detection.
Relationship between trigger conditions
A relationship between trigger conditions on edges and trigger conditions on logic levels can be set
by the user, by using the
Trigger condition menu ring. Several options are available:
•
Edge OR Level:
A trigger condition occurs when one between an edge condition or a
logic level condition is detected;
•
Edge AND Level:
A trigger condition occurs when an edge condition and a logic level
condition are satisfied simultaneously;
•
Edge BEFORE Level:
A trigger condition occurs when an edge condition has been detected
at least once before that on logic levels;
•
Edge AFTER Level:
A trigger condition occurs when an edge condition has been detected
at least once after that on logic levels;
•
ALWAYS:
A trigger condition occurs automatically when data acquisition starts.
Any setting on edges or on logic levels will be ignored;
•
NEVER:
Trigger is inhibited. Any setting on edges or on logic levels will be
ignored. A trigger event, however, can be activated manually during
data acquisition.
Note
: The trigger event is detected in an asynchronous way, independently of the sampling
frequency. If this frequency is too low or an external clock is used, the trigger event, even if
correctly detected, may not be visualized in the Waveform or Data Windows.
Pretrigger, PretriggerHS and DelayHS
The Pretrigger control allows specifying the position in which the trigger event will be located with
respect to the AT-LA500 memory. If the most meaningful data must be sampled after the trigger
detection, low pretrigger percentage must be selected. On the contrary, if signal evolutions before
trigger event must be analyzed, a high pretrigger percentage is more suitable.
The High Speed data have a dedicated PretriggerHS control to set the trigger position respect to the
1kSample HS memory.
It is also possible to insert a programmable delay to shift the High Speed data acquisition to help to
focus the event to examine if this is far from the trigger instant.