National Instruments Low-Cost Multifunction I/O Board for ISA..., User Manual

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Signal Connections Chapter 3
Lab-PC+ User Manual 3-14 © National Instruments Corporation
are connected to the digital lines PC<0..7> for digital I/O Port C. Pin 13, DGND, is the digital
ground pin for all three digital I/O ports.
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
Logical Inputs and Outputs
Digital I/O lines: Minimum Maximum
Input logic low voltage -0.3 V 0.8 V
Input logic high voltage 2.2 V 5.3 V
Output logic low voltage - 0.4 V
(at output current = 2.5 mA)
Output logic high voltage 3.7 V -
(at output current = -2.5 mA)
Darlington drive current
±
2.5 mA
±
4.0 mA
(R
EXT
= 700
Ω
, V
EXT
= 1.7 V)
Figure 3-8 illustrates signal connections for three typical digital I/O applications.