National Instruments Data Acquisition Device E Series - Manual (Page 97)

Chapter 4 Digital I/O
E Series User Manual 4-2 ni.com
or output. At system startup and reset, the DIO ports are all
high-impedance.
The hardware up/down control for general-purpose Counters 0 and 1 are
connected onboard to P0.6 and P0.7, respectively. Thus, you can use P0.6
and P0.7 to control the general-purpose counters. The up/down control
signals, Counter 0 Up/Down and Counter 1 Up/Down, are input-only and
do not affect the operation of the DIO lines. Refer to Chapter 5,
Counters ,
for more information on counters.
(NI 6016 and NI 6025E Devices Only) The NI 6016 and NI 6025E use an
82C55A programmable peripheral interface to provide additional lines of
digital I/O that represent three 8-bit ports. Refer to the Extended Digital I/O
section for more information.
Extended Digital I/O
(NI 6016 and NI 6025E Devices Only) The NI 6016 and NI 6025E use an
82C55A programmable peripheral interface (PPI) to provide an additional
24 lines of DIO that represent three 8-bit ports: P1, P2, and P3. The
82C55A has three modes of operation: simple I/O (mode 0), strobed I/O
(mode 1), and bidirectional I/O (mode 2). In modes 1 and 2, the three ports
are divided into two groups: group A and group B. Each group has eight
data bits, plus control and status bits from Port 3 (P3). Modes 1 and 2 use
handshaking signals from the computer to synchronize data transfers.
NI-DAQmx does not currently support mode 2.
The Example Finder contains examples for programming the 82C55A in
both Traditional NI-DAQ (Legacy) and NI-DAQmx. To locate the
examples, use the keywords
8255 or handshaking .
Port 3 Signal Assignments
(NI 6016 and NI 6025E Devices Only) The signals assigned to port 3 depend on
how the 82C55A is configured. In mode 0, or no handshaking
configuration, port 3 is configured as two 4-bit I/O ports. In modes 1 and 2,
or handshaking configuration, port 3 is used for status and handshaking
signals with any leftover lines available for general-purpose I/O. Table 4-1
summarizes the port 3 signal assignments for each configuration. You can
also use ports 1 and 2 in different modes; Table 4-1 does not show every
possible combination.
Note Table 4-1 shows both the port 3 signal assignments and the terminology correlation
between different documentation sources. The 82C55A terminology refers to the different