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In DDC mode, the NI 5142 has the ability to analog trigger from circuitry located on the daughtercard, or from the OSP circuit located at the output of the DDC. The analog circuit on the daughtercard always triggers on data before any onboard signal processing occurs. The OSP circuit always triggers on data after onboard signal processing occurs.
In DDC mode, the NI 5622 has the ability to analog trigger only from the OSP circuit located at the output of the DDC. The OSP circuit always triggers on data after onboard signal processing occurs.
When the DDC is in complex mode, the OSP circuit triggers on the magnitude of both the I stream and the Q stream. The circuit uses the following formula:
Sqrt (I2 + Q2)
This magnitude is proportional to the power of the signal. By default, the device uses the analog circuit on the daughtercard. You can change the trigger used by the device by using the Ref Trigger Detector Location property or the NISCOPE_ATTR_REF_TRIGGER_DETECTOR_LOCATION attribute.
The OSP trigger circuit can also trigger on the beginning of bursts of data. To enable this functionality, configure the Ref Trigger Minimum Quiet Time property or the NISCOPE_ATTR_REF_TRIGGER_MINIMUM_QUIET_TIME attribute to the value of time that corresponds to the amount of time that the signal must be below the trigger level to constitute a quiet time. For more information, refer to Burst Triggers.