Teledyne SP Devices ADQ8-8C, Manual

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17-2000 C
2020-09-17
20(50)
ADQ8-8C Manual
17-2000 C 2020-09-17
20(50)
4.6.3 Synchronous trigger
A synchronous trigger is phase locked to the clock of the digitizer. The trigger source needs access to
the clock reference of the digitizer. There are three ways to achieve this synchronization:
1. Output the internal clock reference of the ADQ and send it to the trigger source,
Section 5.10 .
2. Use the clock reference of the trigger source as clock reference for the ADQ, Section 5.6 .
3. Use the internal trigger of the ADQ and output it to trigger the external equipment, Section 4.11 .
When the trigger is phase-locked to the clock reference the timing is comparable to a digital signal
which defines setup and hold time.
4.6.4 Extended trigger resolution
The basic sampling process maps the trigger to the sampling rate of the digitizer. There is also addi-
tional trigger time information available; Extended trigger resolution,
Figure 11 .
The Trigger Clock is operating at 4 GHz. This means that the time resolution of the trigger input TRIG is
reduced to 250 ps.
Note: The extended trigger resolution is available on triggers connected to TRIG only.
The extended trigger information is included in the timestamp information,
Section 4.4 .
The position of the first sample is rounded up from the trigger position. The parameter
RECORD_START
tells where the trigger was. Referring to Figure 11 , the
RECORD_START
parameter can have values in
the range –250 ps up to +500 ps. A positive value means that the first sample is after the trigger. The
given range is without pretrigger or trigger delay. With pretrigger or trigger delay, the
RECORD_START
will have a larger (absolute) value.
4.7 Software trigger
The software trigger is a user command that triggers the ADQ. This is for direct user control of the
acquisition and is useful for looking at continuous signals where the timing of the trigger is not critical.
The software trigger is sent through several layers of software and the time when it arrives to the digi-
tizer cannot be predicted. However, the time when it actually arrived can be read from the time stamp in
the record header,
Section 4.4 .
The software trigger may also be used for time-out function. This is a way to discover faults in the
setup. When the device do not trigger for some reason within a certain time frame, a software com-
mand sequence may be sent and the data can be analyzed to find out what is wrong,
Example 4 .
Example 4: A time-out function using software trigger can be implemented like this:
1. Time-out occurs
Figure 11: Extended trigger resolution timing for ADQ8-8C .
,