User`s guide

64 • Operation Theory
In PCI form factor, there is a connector on the top right corner of the card
for the SSI. Refer to section 2.3 for the connector position. All the SSI sig-
nals are routed to the 20-pin connector from the FPGA. To synchronize
multiple cards, users can connect a special ribbon cable (ACL-SSI) to all
the cards in a daisy-chain configuration
In PXI form factor, we utilize the PXI trigger bus built on the PXI backplane
to provide the necessary timing signal connections. All the SSI signals are
routed to the P2 connector. No additional cable is needed. For detailed
information of the PXI specifications, please refer to PXI specification Re-
vision 2.0 from PXI System Alliance (www.pxisa.org).
The 6 internal timing signals could be routed to the SSI or the PXI trigger
bus through software drivers. Please refer to section 4.6.1 for detailed in-
formation of the 6 internal timing signals. Physically the signal routings are
accomplished in the FPGA. Cards that are connected together through the
SSI or the PXI trigger bus, will still achieve synchronization on the 6 timing
signals.
The mechanism of the SSI/PXI
1. 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 ADCONV
signal for 4 DAQ /PXI-22XX 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 acquisition. 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 SI_counter, SI2_counter, NumChan_counter and the post
scan counter (PSC) on all other cards.
e. Start DMA operations for all cards, thus all the cards are
waiting for the trigger event.