National Instruments Data Acquisition Device NI USB-621x - Manual (Page 81)

© National Instruments Corporation 6-1 NI USB-621x User Manual
6
Digital I/O
Refer to one of the following sections, depending on your device:
• Digital I/O on USB-6210/6211/6215/6218 Devices—
USB-6210/6211/6215/6218 devices have up to eight lines of digital
inputs (DI) and up to eight lines of digital output (DO).
• Digital I/O on USB-6212/6216 Devices —USB-6212/6216 devices
have up to 32 bidirectional static digital I/O (DIO) lines.
Digital I/O on USB-6210/6211/6215/6218 Devices
USB-6210/6211/6215/6218 devices have up to eight static digital input
lines, P0.<0..7>. These lines also can be used as PFI inputs.
USB-6210/6211/6215/6218 devices have up to eight static digital output
lines, P1.<0..7>. These lines also can be used as PFI output. By default the
digital output lines are disabled (high impedance with a 47 k
Ω pull-down
resistor) on power up. Software can enable or disable the entire port
(software cannot enable individual lines). Once the port is enabled, you can
individually configure each line to the following:
• Set a line to a static 0
• Set a line to a static 1
• Export a timing output signal to a line as a PFI pin
The voltage input and output levels and the current drive level of the DI and
DO lines are listed in the NI USB-621x Specifications. Refer to Chapter 7,
PFI , for more information on PFI inputs and outputs.
Figure 6-1 shows the circuitry of one DI line and one DO line. The
following sections provide information about the various parts of the DIO
circuit.