User manual

Chapter 3 Software Overview

immediate digital operations. However, both groups cannot be configured

for input or output at the same time.

Although a group can consist of non-contiguous lines, there is no logical

grouping of the lines, and an 8-bit value is still passed from the input

function or returned from the output function. For example, if a group is

configured for output with lines 0,1,2,4, and the group is to be written with

all ones, the hex value of 0x17 is passed to the function instead of 0xF.

Group operations are buffered operations only, which means immediate

digital operations are not possible with these devices using handshaking.

Because all group operations are buffered, there is no support for a status

operationindicatingwhenaninputoperationhasbeenlatchedtooran

output operation latched from the digital lines. Instead, group operations

are done from a buffer. In the case of digital output operations, values are

written to a buffer and latched onto the digital lines when the appropriate

edge from a clock signal is detected. For digital input operations, values are

latched from the digital lines to the buffer when the appropriate edge of the

clock signal is detected. Either a rising edge or a falling edge of the clock

signal can be specified for latching the values. The clock source can be a

timing signal used internally or generated external to the board, and it must

be routed to one of the RTSI lines.

Digital I/O Functions

The digital I/O (

DIG

) functions perform nonhandshaked digital line and

port I/O.

Refer to the NI-DAQ Function Reference Online Help file to determine

which functions your device supports.

DIG_In_Line

Returns the digital logic state of the

specified digital input line in the

specified port.

DIG_In_Prt

Returns digital input data from the

specified digital I/O port.

DIG_Line_Config

Configures the specified line on a specified

port for direction (input or output).

DIG_Out_Line

Sets or clears the specified digital output

line in the specified digital port.