National Instruments 653X Manuale Utente
Chapter 2
Using Your 653X
© National Instruments Corporation
2-3
Advantages of using the wired-OR driver include:
•
The ability to connect two or more wired-OR outputs together without
damaging the drivers.
damaging the drivers.
•
The ability to connect wired-OR outputs to open-collector drivers,
to GND signals, or to switches connecting to GND signals, without
damaging the drivers.
to GND signals, or to switches connecting to GND signals, without
damaging the drivers.
•
The ability to use wired-OR outputs bidirectionally. If you connect
wired-OR outputs together, you can read back the value of a pin to
determine if any connected outputs are logic low.
wired-OR outputs together, you can read back the value of a pin to
determine if any connected outputs are logic low.
Using Control Lines as Extra Unstrobed Data Lines
The 653X device has two timing controllers for high-speed data transfer
(Group 1 and Group 2). Each group contains four control lines which can
be used to time the input/output of data with hardware precision. You can
use Groups 1 and 2 to:
(Group 1 and Group 2). Each group contains four control lines which can
be used to time the input/output of data with hardware precision. You can
use Groups 1 and 2 to:
•
Generate or receive digital patterns and waveforms at regular intervals
or timed by an external TTL signal.
or timed by an external TTL signal.
•
Transfer data between two devices using one of six configurable
handshaking protocols.
handshaking protocols.
•
Acquire digital data every time the state of a data line changes.
Note
If you configure either group to perform handshaking I/O or pattern I/O, the
associated timing control lines for that group will not be available for unstrobed I/O.
If you are not using Group 1 and/or Group 2 as timing controllers to
perform pattern I/O or handshaking I/O, you can use their control lines as
extra data lines. These lines constitute Port 4. The direction and output
driver type of these lines are not configurable—four lines are used as input
only and four are used as standard output only. Even though there are eight
actual lines, the port width for Port 4 is 4 bits. In software, these lines are
collectively referred to as Port 4; when writing to Port 4, the output lines
are affected, and when reading from Port 4, the input lines are read.
Table 2-1 displays how Port 4 lines are organized.
perform pattern I/O or handshaking I/O, you can use their control lines as
extra data lines. These lines constitute Port 4. The direction and output
driver type of these lines are not configurable—four lines are used as input
only and four are used as standard output only. Even though there are eight
actual lines, the port width for Port 4 is 4 bits. In software, these lines are
collectively referred to as Port 4; when writing to Port 4, the output lines
are affected, and when reading from Port 4, the input lines are read.
Table 2-1 displays how Port 4 lines are organized.