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E1437A User's Guide
VXI plug&play Programming Reference
Description
An E1437 can be triggered to collect data in a variety of ways. The trigger can be
internally generated or can come from an external source. Multiple modules can be
triggered synchronously. A variable pre- and post-trigger delay can be programmed for
data collection. The slope and level of the trigger point on a signal can be selected. The
source of the internal trigger can be either the output of the ADC or the magnitude of
the complex output of the decimation filter.
hpe1437_trigger_setup is the function that sets all trigger parameters at once. An
E1437 will generate a trigger only when it is in the TRIGGER state and the SYNC line on
the VXI backplane is released. When a trigger is generated, the E1437 will release the
SYNC line.
Parameters
id is the VXI instrument session pointer returned by the hpe1437_init function.
tType determines the trigger source. HPE1437_ADC generates a trigger based on the
raw data samples from the ADC. HPE1437_MAG generates a trigger based on the log
magnitude of the signal after it has been filtered to a selectable bandwidth around the
center frequency established by the hpe1437_frequency_setup function.
HPE1437_EXTERNAL uses transitions on the signal applied to the BNC external
trigger connector on the front panel. HPE1437_USER disables the module from any
event-driven trigger generation though it is still possible to force the module to trigger a
measurement by pulling the SYNC line once the module is in the trigger state. You may
do this by calling the hpe1437_meas_start function, waiting for the module to reach
the trigger state, then triggering the measurement by using hpe1437_meas_control to
pull the SYNC line. HPE1437_IMMEDIATE triggers a measurement immediately upon
entering the trigger state.
NOTE
In multi-module systems all modules should be of the same type in order to have
the same actual delay.
tTypePtr contains the current value of tType.
delay is the time delay, in units of output samples, between when a trigger is received
and the first data point in the output data. Negative values indicate a pre-trigger
condition, where samples prior to the trigger event are included in the output data. The
amount of pre-trigger delay is limited to the number of samples which can be saved in
the 8 Mbyte buffer memory. See the hpe1437_data_setup function description for the
number of bytes used per sample. The delay limits depend on the data type as follows:
=====================================================================
=====================================================================
—————————————————
Post-trigger
Pre-trigger
—————————————————
If delay is <132-DRAMsize/8 or >16,777,116 a bad parameter
error will be set. However, the delay is still programmed in order to
accommodate the valid setups generated by other data types.
delayPtr contains the current value of the of delay.
4-62
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Trigger Delay
(DRAM size in bytes)
|
|
32 bit real
|
32 bit complex
|
16 bit complex
|
16,777,116
|
|
132-DRAMsize/8
|
164-DRAMsize/4
|
|
16 bit real
33,554,332
|
67,108,764
|
228-DRAMsize/2
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