
Chapter 20 DSA Devices
DAQ Hardware Overview Guide 20-6 www.ni.com
NI 455
X
Digital I/O
The NI 455X devices contain four 8-bit digital I/O ports supplied by the
DAQ-TIO chip. These ports are referred to as ports 0 through 3 by the
Digital I/O functions.
You can configure each port entirely as either an input or an output port, or
you can configure individual lines for either input or output. Each port and
line has read-back capability, and these ports operate in nonlatched mode
only.
Note
The pins on the I/O connector that correspond to digital port 3 are the same pins that
correspond to the inputs and outputs of the two general-purpose counters. Thus, if you
configure any lines of port 3 for digital input or output, you disable the counters from using
the lines as input or output signals if a counter operation has been previously configured.
Similarly, enabling the counter input and output signals disables the digital signals on the
corresponding lines. National Instruments recommends that you do not use digital port 3
if you are using counters and vice versa.
PCI-445
X
and NI 455
X
Counter/Timer Operation
This section contains information regarding the operation of the
counter/timer for the 445X and 455X.
PCI-445
X
Counter/Timers
The PCI-445X devices use the National Instruments DAQ-STC
counter/timer chip. The DAQ-STC has two 24-bit counter/timers that are
always available for general-purpose counter/timer applications.
Note
When synchronizing multiple devices for master/slave operations, GPCTR0 on
slave devices are reserved for internal use and are not available for general use.
Refer to the
GPCTR functions in the NI-DAQ Function Reference Online
Help for more information.
NI 455
X
Counter/Timers
The NI 455X devices use the National Instruments DAQ-TIO
counter/timer chip. The DAQ-TIO has two 32-bit counter/timers that are
always available for general-purpose counter/timer applications. Refer to
the
GPCTR
functions in the NI-DAQ Function Reference Online Help for
more information.
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