Table 3-6. Logic Family Thresholds* - National Instruments NI 4350 User Manual

Note:
© National Instruments Corporation
If the number of digital input lines is not adequate for your 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 3-6 shows the thresholds of CMOS and TTL logic
families using analog inputs as digital inputs.
Logic Family
CMOS
TTL
* Check your logic family data sheets for any variations.

Table 3-6. Logic Family Thresholds*

Low
< 0.8 V
< 0.8 V
3-29
Chapter 3 NI 4350 Operation
High
> 2.0 V
> 2.0 V
NI 4350 User Manual