Astronics OMNIBUS II NI PXIe, User Manual

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OmniBus II NI PXIe User Manual 5-1
5. OMNIBUS II PXIE SPECIFIC FEATURES
This chapter describes features available only on OmniBus II PXIe products.
OmniBus II PXIe is a Type 2 Compact PCI Express (cPCIe) card with eXtensions
for Instrumentation (PXIe). As such, PXIe cards can be used in either cPCIe or
PXIe systems.
5.1 Clock Switch (CLK SEL)
The OB2 PXIe protocol circuitry can use either the onboard 100 MHz oscillator or
the PXIe connector’s
PXIe_CLK100
input. Selecting the onboard oscillator
(OSC) allows the PXIe card to be installed in a cPCIe system which does not
support the
PXIe_CLK100
input. The clock can be selected (prior to applying
power) by sliding the yellow switch (SW1) as shown below. The switch setting is
sampled once at power on to guarantee a stable clock selection value.
Note: The yellow switch is not a jumper, thus the switch cannot be removed
from the card. Refer to Section 5.4 for more information about reading the
clock switch status.
Figure 5.1—PXIe Onboard Clock Switch
If the card does not have a valid clock due an incorrect switch setting, the software
will return
ERR_NOCLK
when accessing the card. Incorrectly setting the clock
switch may cause the host computer to freeze when the card is accessed.
5.2 PXIe Trigger Access
The following table shows the PXIe Trigger signals supported by the OB2 PXIe
card. All signals are asynchronous to either
CLK10
or
CLK100
. You can access
PXIe Trigger signals through the BTICard_ExtDIORd ,
BTICard_ExtDIOWr
, and
BTICard_ExtDIOEnWr
functions by passing in
the associated dionum as per Table 5.1. You can also monitor these signals using
BTICard_ExtDIOMonConfig
with banknum and rise_edge / fall_edge bits as
per Table 5.1. For more information on these functions, refer to the API manuals
(e.g.,
MIL-STD-1553 Programming Manual for BTIDriver-Compliant Devices ).