ADLINK PXI-2022 - Manual (Page 50)

42 Function Block and Operation Theory
The SSI/PXI mechanism
1. We adopt master-slave configuration for SSI/PXI. In a
system, for each timing signal, there shall be only one
master, and other cards are SSI slaves or with the SSI
function disabled.
2. For each timing signal, the SSI master doesn’t have to
be in a single card.
For example:
We want to synchronize the A/D operation through the
SSI_ADCONV signal for 4 PXI-2020/2022 cards. Card 1 is
the master, and Card 2, 3, 4 are slaves. Card 1 receives an
external digital trigger to start the post trigger mode acquisi-
tion. The SSI setting could be:
a.Set the SSI_ADCONV signal of Card 1 to be the master.
b.Set the SSI_ADCONV signals of Card 2, 3, 4 to be the
slaves.
c.Set external digital trigger for Card 1’s A/D operation.
d.Set the SI_counter and the post scan counter (PSC) of all
other cards.
e.Start DMA operations for all cards, thus all the cards are
waiting for the trigger event.
When the digital trigger condition of Card 1 occurs, Card 1 will
internally generate the ADCONV signal and output this ADCONV
signal to SSI_ADCONV signal of Card 2, 3 and 4 through the SSI/
PXI connectors. Thus we can achieve 8/16-channel acquisition
simultaneously for PXI-2020 and PXI-2022, correspondingly..
You could arbitrarily choose each of the 4 timing signals as the SSI
master from any one of the cards. The SSI master can output the
internal timing signals to the SSI slaves. With the SSI, users could
achieve better card-to-card synchronization.
Note that when power-up or reset, the DAQ timing signals are
reset to use the internal generated timing signals.