National Instruments VXI-MXI-Express Series User Manual page 64

Appendix D Using the Trigger Ports on the NI VXI-8360LT
LXI Compatibility
Connecting the Trigger Port Cables
Note Trigger bus cables may be removed and inserted while power is on.
Configuring the Wired Trigger Bus
VXI-MXI-Express Series User Manual
The physical and electrical interface of the wired VXI backplane trigger
bus is compatible with the LXI wired trigger bus. The physical interface
uses the standardized 25-pin micro-D type connector. The electrical
interface uses the LXI-wired Trigger Bus cable and Terminator 2.0
specified Texas Instruments (SN65MLVD080) bus transceiver.
The LXI wired trigger bus has a much broader triggering definition and can
be considered as a superset of the VXI-8360LT's wired VXI backplane
trigger bus. The two trigger domains are compatible with a few constraints:
1. All LXI devices that share the wired VXI backplane trigger bus must
be configured for active high assertion of triggers whether in Driven
mode or Wired-OR mode.
2. The LXI specification states that each trigger channel shall be
individually configurable as an input or output (or both). The NI VXI
driver software allows a trigger be mapped In to the Frame (input) or
Out of the Frame (output) but not both. This constrains a single
trigger to be either a driver or a receiver.
The physical pinout for the two trigger ports is identical so there are no
special cable connection requirements between the ports.
End of bus termination is required for proper operation. Use two 50 Ω
resistors in series across each trigger differential pair with the center tap
decoupled to ground with a capacitor. Commercially available terminators
are recommended.
The 8 triggers in the wired VXI backplane trigger bus are configured via
hardware and software. Hardware switches located on the top edge of the
NI VXI-8360LT control the operating mode of the trigger. The factory
default switch settings for all 8 triggers are displayed in Figure D-1,
Trigger Configuration Sticker (Located on the Side of the NI
D-2
VXI-8360LT).
ni.com