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Signal Connections Chapter 3
DAQCard-700 User Manual 3-12 © National Instruments Corporation
Digital I/O Signal Connections
Pins 22 through 37 of the I/O connector are digital I/O signal pins. Pins 22 through 29 are digital
input pins. Pins 30 through 37 are digital output pins. Pins 19 and 50 are digital ground pins.
The following specifications and ratings apply to the digital I/O lines.
• Absolute maximum voltage input rating +5.5 V with respect to DGND
-0.5 V with respect to DGND
• Digital input compatibility TTL-compatible
• Input current (high or low level) 1 mA
• Digital output compatibility TTL-compatible
• Output current source capability 4 mA, at V
OH
= 2.7 V
• Output current sink capability 4 mA, at V
OL
= 0.5 V
Figure 3-6 shows an example of connections to the digital input and output ports. Digital input
applications include receiving TTL signals and sensing external device states such as the switch
in Figure 3-6. Digital output applications include sending TTL signals and driving external
devices such as the LED shown in Figure 3-6.