Chapter 3
Signal Connections
©
National Instruments Corporation
3-17
Logical Inputs and Outputs
•
Absolute max voltage rating
–0.5 to +5.5 V with respect to DGND
•
Digital I/O lines:
–
Input logic low voltage
–0.3 V min
0.8 V max
–
Input logic high voltage
2.2 V min
5.3 V max
–
Output logic low voltage
—
0.4 V max
(at output current = 2.5 mA)
–
Output logic high voltage
3.7 V min
—
(at output current = –2.5 mA)
–
Input leakage current
–1 µA min
1 µA max
(0 < V
in
< 5 V)
Figure 3-8 illustrates signal connections for three typical digital I/O
applications.
Figure 3-8.
Digital I/O Connections
In Figure 3-8, port A is configured for digital output, and ports B and C are
configured for digital input. Digital input applications include receiving
TTL signals and sensing external device states such as the switch in
TTL Signal
13
DGND
I/O Connector
PCI-1200
30 PC0
22 PB0
+5 V
+5 V
LED
14 PA0
Port A
PA<7..0>
Port B
PB<7..0>
Port C
PC<7..0>
