Signal Connections
Chapter 3
DAQCard-500 User Manual
3-6
© National Instruments Corporation
•
Digital input compatibility
TTL-compatible
•
Input current (high or low level)
1 µA
•
Digital output compatibility
TTL-compatible
•
Output current source capability
4 mA, at V
OH
= 3.3 V
•
Output current sink capability
4 mA, at V
OL
= 0.9 V
Figure 3-3 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 3-3. Digital output applications include sending TTL signals and driving external
devices such as the LED shown in Figure 3-3.
TTL Signal
Digital
Input
Port
Digital
Output
Port
12 DIN0
27
DGND
I/O Connector
DAQCard-500
LED
+5 V
+5 V
15 DIN3
16 DOUT0
Figure 3-3. Digital I/O Signal Connections
Note: Pin numbers in this figure refer only to the PR27-30F cable.