Chapter 2
NI 2565 Operation
2-6
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National Instruments Corporation
Scanner Advanced
The NI 2565 can generate a scanner advanced trigger to indicate when the
switch card is set up and ready to take measurements. Using the driver
software, you can configure the switch card to route the scanner advanced
(SCANADV) trigger to any PXI TTL trigger line or to the PXI star trigger.
You can configure the switch card to generate the SCANADV trigger when
a relay has settled (or debounced).
Because the NI 2565 has open collector drives on the PXI TTL trigger
lines, you can have multiple switch cards using the same trigger line in the
multicard SCANADV mode.
Modes
SCANADV has two modes of operation. In its default mode, the
SCANADV trigger asserts for 1 µs after the relay has debounced. You
can also configure the switch card for handshaking mode, in which the
SCANADV trigger goes high after a relay settles, and the SCANADV
trigger goes low after the external trigger input asserts. You can use this
handshaking mode for multicard scanning.
Note
The NI 2565 ignores external triggers when it is not in a wait-for-trigger state
while scanning.
Initiating Scanning
When you use the NI 2565 to initiate a scan, make sure the measurement
device is armed (waiting for trigger) before enabling scanning on the
switch card. Enabling scanning causes the first switch(es) in the scan list to
close and generates a scanner advanced trigger after the relay switches have
settled or debounced.
When you use the measurement device to initiate a scan, make sure
scanning is enabled on the NI 2565 before the measurement device starts to
take measurements. This ensures that the switch card has the correct signal
routed and that the switch card is waiting for an external trigger from the
measurement device.
Always configure the triggers in a system before configuring the
measurement device or the NI 2565 for scanning. When triggers are
configured, a state change or pulse could occur on the trigger line.
This is also possible when you reset the switch card.
