180 Chapter 12: System Configuration TempScan / MultiScan User's Manual
To enable the gap-free acquisition with two timebases, you must perform the following:
•
Specify the two trigger events – the Trigger (trigger start event) and the Stop (trigger stop event) –
via the Set Trigger Configuration (
T
) command.
• Set the two timebase intervals – the normal and the acquisition scan intervals – via the Set Scan
Interval (
I) command.
• Set the Pre-Trigger count to
-1, via the pre parameter of the Set Counts (Y) command. If more
than one transition cycle is desired, enable the Auto Re-arm flag of the Set Trigger Configuration
(
T) command to allow each transition cycle to be stored in its own Trigger Block within the buffer.
Using this method, continuous data may be collected as long as the application program can read data
out of the Acquisition Buffer before the buffer overruns. If the buffer overruns, the data read may not
be continuous.
Trigger Configuration
Trigger Start & Stop Events
The programmed system events are the driving force behind any acquisition. For an acquisition to take
place, the Set Trigger Configuration (
T) command is used as the central command to assign the
following events to the TempScan/1100 or MultiScan/1200 unit: The Trigger (trigger start event) and
the Stop (trigger stop event). The Trigger and Stop may also be assigned different trigger sources. In
addition, the Set Trigger Configuration (
T) command also determines whether or not, after the initial
acquisition, the acquisition will be re-enabled automatically, and whether or not the Trigger (trigger
start event) should be synchronized with the Pre-Trigger scan interval.
Upon the execution of this command, the unit will enter acquisition mode, and the TRIGGER LED
indicator on the front panel will flash. If Pre-Trigger scans have been configured via the Set Counts
(
Y) command, then the sampling for Pre-Trigger data will begin at this time. Specifically, the Set
Trigger Configuration (
T) command is used to set the following parameters:
• Trigger (trigger start event): This parameter is the event that is to take place in order for the unit
to begin acquiring scans. When the unit detects a Trigger, it will stop acquiring Pre-Trigger scans
(if configured), and begin acquiring Post-Trigger scans at that point. The first of these Post-
Trigger scans, the Trigger scan, will be Time/Date stamped for later reference, such as in a
response to the following User Status (
U) command query: U6 – Query the Buffer Status String.
Also, when the Trigger is detected, the Triggered Bit (Bit 1) of the Status Byte Register (
STB) will
be set and the TRIGGER LED indicator on the front panel will turn on.
• Stop (trigger stop event): This parameter is the event that is to take place in order for the unit to
stop acquiring scans. When the unit detects a Stop, it will stop acquiring Post-Trigger scans at that
point, unless Post-Stop scans are defined via the Set Counts (
Y) command. The last of these Post-
Trigger scans, the Stop scan, will be Time/Date stamped for later reference, such as in a response
to the following User Status (
U) command query: U6 – Query the Buffer Status String. Also, when
the Stop is recognized, the Triggered Bit (Bit 1) of the Status Byte Register (
STB
) will be cleared
and the TRIGGER LED indicator on the front panel will turn off.
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