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3.7.4 Comparing the Different Trigger Sources from SSI
When selecting TRSRC_SSI_1 as the trigger source input, the signal SSI_TRIG1 reflects the
trigger event signal in an acquisition sequence. However, when synchronizing multiple PCI/
PXI-69816/ 26/46 devices, each module may recognize the trigger signal with one-clock
time difference because the signal is not related to the timebase.
There is another phenomenon if using TRSRC_SSI_2 in pre-trigger and middle-trigger
mode. The operation start signal is generated by a software command so multiple PCI/PXI-
69816/26/46 modules don’t start the data acquisition simultaneously, which may result in
the fact that the amount of stored samples are different if the trigger event occurs before
the specified amount of data has been acquired.
When selecting TRSRC_SSI_2 as the trigger source input, SSI_TRIG2 and SSI_START_OP can
achieve better synchronization between multiple PCI/PXI-69816/26/46 devices. A clocked
SSI_TRIG2 can guarantee all PCI/PXI-69816/26/46 devices recognize the trigger event at the
same clock edge if they use the same timebase. In pre-trigger and middle-trigger mode,
SSI_START_OP guarantees all the PCI/PXI-69816/26/46 devices start the data acquisition
at the same time.
