Chapter 4 Signal Connections

PCI-4451/4452 User Manual 4-6

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National Instruments Corporation

Table 4-3. Digital I/O Connector Pin Assignment
Signal Name Reference Direction Description
DIO<0..7> DGND Input or
Output Digital I/O channels 0 through 7—Channels 6 and 7 can
control the up/down signal of general-purpose counters 0
and1, respectively.
DGND — — Digital Ground—This pin supplies the reference fo r the digital
signals at the I/O connector as well as the +5 VDC supply.
+5 V DGND Output +5 VDC Source—These pins are fused for up to 1 A of +5 V
supply. The fuse is self-resetting.
RESERVED1 DGND Output RESERVED—This pin is reserved. This signal is always high.
EXTSTROBE* DGND Output External Strobe—This signal can be toggled under software
control to latch signals or trigger events on external devices.
PFI0/TRIG1 (EXT_TRIG) DGND Input
Output
TRIG1—As an input, this is a source for the data acqui sition
trigger.
As an output, this signal can drive external applications to
indicate that a trigger on the device has occurred. TRIG1 is the
start acquisition signal.
In LabVIEW, referred to as AI Start Trigger for both i nput and
output.
PFI1/TRIG2 (PRETRIG) DGND Input
Output
PFI1/TRIG2 (PRETRIG)—As an input, this is one of the
PFIs.
As an output, this is the TRIG2 signal. In pretrigger
applications, a low-to-high transition indicates the initia tion of
the posttrigger conversions. TRIG2 is not used in posttrigger
applications.
In LabVIEW, referred to as AI Stop Trigger for both input and
output.
CONVERT* DGND Output A high-to-low edge on CONVERT* indicates that an A/D
conversion is occurring.
In LabVIEW, referred to as AI Convert.
PFI3/GPCTR1_SOURCE DGND Input
Output
PFI3/Counter 1 Source—As an input, this is one of the PFIs.
As an output, this is the GPCTR1_SOURCE sign al. This signal
reflects the actual source connected to the general-purpose
counter 1.
PFI4/GPCTR1_GATE DGND Input
Output
PFI4/Counter 1 Gate—As an input, this is one of the PFIs.
As an output, this is the GPCTR1_GATE signal. This signal
reflects the actual gate signal connected to the general-purpose
counter 1.
UPDATE* DGND Output A high-to-low edge on UPDATE* indicates that a D/A
conversion is occurring.
In LabVIEW, referred to as AO Update.
User.book Page 6 Tuesday, April 14, 1998 10:20 AM