National Instruments NI 435 Series, User Manual, Page: 47 / 77

Chapter 2 Operating the NI 435x Device
© National Instruments Corporation 2-29 NI 435x User Manual
Figure 2-12. Examples of DIO Applications
Caution To prevent possible safety hazards, the voltage applied to the digital I/O lines
should never be outside –0.5 V and +5.5 V, with respect to DGND.
The DIO lines of the NI 435 x are protected against damage from voltages
within –0.5 and +5.5 V with respect to digital ground (DGND). Never
apply voltages above these levels to these signals.
Note If the number of digital input lines is not adequate for the application, you can use
the analog input channels to measure the voltage of the digital signal you want to measure.
Then you can determine the logic level based on the thresholds of the logic family of the
digital signal you are monitoring. Table 2-6 shows the thresholds of CMOS and TTL logic
families using analog inputs as digital inputs.
+5 V
DIO0 (configured as an output)
DIO1 (configured as an input)
DIO2 (configured as an input)
DIO3 (configured as an input)
DIO3 (configured as an output)
DGND
R
4
R
1
R
2
R
3
SW
LED
TTL or CMOS
NPN Transistor