8

Digital I/O

This chapter explains digital I/O for data acquisition.

Things You Should Know about Digital I/O

Digital I/O interfaces often are used to control processes, generate patterns for testing, and communicate with peripheral equipment such as heaters, motors, and lights. Digital I/O components on DAQ devices and

SCXI modules consist of hardware parts that generate or accept binary on/off signals, where on is typically 5 V and off is 0 V.

As shown in Figure 8-1, all digital lines are grouped into ports on DAQ devices and banks on SCXI modules. The number of digital lines per port or bank is specific to the particular device or module used, but most ports or banks consist of four or eight lines. Except for the 653X (DIO-32HS) in unstrobed mode, TIO-10, and E Series devices, the lines within the same port or bank must all be of the same direction (must either be all input or all output), as shown in Figure 8-1. By writing to or reading from a port, you can simultaneously set or retrieve the states of multiple digital lines.

Output Lines

Input Port

Data latches and drivers

Input Lines

Device or Module

Figure 8-1. Digital Ports and Lines