User manual

Chapter 3 Software Overview

into an input port. The handshaking mode for the PCI 6115 and the

PCI-6120 is slightly different and is more appropriately called a

clocking mode. In the clocking mode, no two-way handshaking signals

are generated. Instead, data is latched in or latched out when a pulse

from a clock signal is detected.

Note

On the 653X, DIO-32F, PCI-6115, and PCI-6120 devices, you must assign ports to

a group before you can use handshaking mode.

Process control applications, such as controlling or monitoring relays,

often use the no-handshaking mode. Communications applications, such as

transferring data between two computers, often use the handshaking mode.

DIO-24, 6025E, AT-MIO-16DE-10, DIO-96, and Lab and

1200 Device Groups

You can group together any combination of ports 0, 1, 3, 4, 6, 7, 9, and 10

on the DIO-96, ports 0 and 1 on the DIO-24 and Lab and 1200 devices,

and ports 2 and 3 on the 6025E devices and AT-MIO-16DE-10 to make up

larger ports. For example, with the DIO-96 you can program ports 0, 3, 9,

and 10 to make up a 32-bit handshaking port, or program all eight ports to

make up a 64-bit handshaking port. See Digital I/O Application Tips later

in this chapter and the

DIG_SCAN_Setup

function description in the

NI-DAQ Function Reference Online Help file for more details.

DIO-32F and 653X Device Groups

On the DIO-32F and 653X devices, you can assign ports 0 through 3

(referring to ports DIOA through DIOD) to one of two groups for

handshaking. These groups are referred to as group 1 and group 2. Group 1

uses handshake lines REQ1andACK1. Group 2 uses handshake lines

REQ2 and ACK2. The group senses the REQ line. An active REQ signal is

an indication that the group must perform a read or write. The group drives

the ACK line. After the group has performed a read or write, it drives the

ACK line to its active state. Refer to your device user manual for more

information on the handshaking signals.

A group can be 8, 16, or 32 bits wide. An 8-bit group can be port 0, 1, 2,

or 3. A 16-bit group can be ports 0 and 1 or ports 2 and 3. A 32-bit group

is all four ports.

After you have assigned ports to a group, the group acts as a single entity

controlling 8, 16, or 32 digital lines simultaneously. The DIO-32F has