ADLINK PCI-9846 - Manual (Page 60)

50 Operation Theory
For enabling output operations, you can use the function
SSI_SourceConn() to output the SSI_TRIG2 and SSI_START_OP
signals.
For the input operations, you can select TRSRC_SSI_2 to set
SSI_TRIG2 and SSI_START_OP as the source of the trigger
event and operation start signal.
Figure 3-24: SSI_START_OP Output and Input Timing Characteristics
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-9816/
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-trig-
ger and middle-trigger mode. The operation start signal is gener-
ated by a software command so multiple PCI/PXI-9816/26/46
modules don’t start the data acquisition simultaneously, which
may result in the fact that the amount of stored samples are differ-
ent 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 synchroniza-
SSI_START_OP
(Output)
Two
Two = 2 TIMEBASE Clocks
Twi
Twi = 20 ns minimum
SSI_START_OP
(Input)