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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 OmniBus II PXIe protocol circuitry can use either the on-board 100MHz
oscillator or the PXIe connector’s PXIe_CLK100 input. Selecting the on-board
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 On-Board 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.
OmniBus II PCIe/PXIe User’s Manual 5-1