National Instruments PCI-1200 User Manual page 46

Signal
Source
I/O Connector
© National Instruments Corporation
frequency measurement application. You can also use a second counter to
generate the gate signal in this application. If you use a second counter,
you must externally invert the signal.
Gate
Source
Figure 3-15. Frequency Measurement Application
The GATE, CLK, and OUT signals for counters B1 and B2 are available at
the I/O connector. The GATE and CLK pins are internally pulled up to +5 V
through a 100 kΩ resistor. Refer to Appendix A, Specifications, for signal
voltage and current specifications.
The following specifications and ratings apply to the 82C53 I/O signals:
• Absolute max voltage input rating –0.5 to +5.5 V,
• 82C53 digital input specifications (referenced to DGND):
– V input logic high voltage
ih
– V input logic low voltage
il
– Input load current
+5 V
100 kΩ
CLK
GATE
13 DGND
NI PCI-1200
with respect to DGND
2.2 V min
–0.3 V min
–10 µA min
3-25
Chapter 3 Signal Connections
OUT
Counter
5.3 V max
0.8 V max
+10 µA max
NI PCI-1200 User Manual