Configuration and Installation
Chapter 2
AT-MIO-16D User Manual
2-40
© National Instruments Corporation
For time-lapse measurement, program a counter to be edge gated. Apply an edge to the counter
GATE input to start the counter. You can program the counter to start counting after receiving
either a high-to-low edge or a low-to-high edge. If the counter is programmed to count an internal
timebase, then the time lapse since receiving the edge is equal to the counter value multiplied by the
timebase period.
To measure frequency, program a counter to be level gated and the rising or falling edges are
counted in a signal applied to a SOURCE input. The gate signal applied to the counter GATE
input is of some known duration. In this case, program the counter to count either rising or falling
edges at the SOURCE input while the gate is applied. The frequency of the input signal is then the
count value divided by the known gate period. Figure 2-38 shows the connections for a frequency
measurement application. You could use a second counter to generate the gate signal in this
application.
Signal
Source
33
DIG GND
Counter
OUT
SOURCE
GATE
+5 V
4.7 k
Ω
MIO-16 I/O Connector
AT-MIO-16D Board
Gate
Source
Figure 2-38. Frequency Measurement Application
Two or more counters can be concatenated by tying the OUT signal from one counter to the
SOURCE signal of another counter. You can then treat the counters as one 32-bit or 48-bit
counter for most counting applications.
The GATE, SOURCE, and OUT signals for Counters 1, 2, and 5, and the FOUT output signal are
tied directly from the Am9513A input and output pins to the I/O connector. In addition, the
GATE, SOURCE, and OUT1 pins are pulled up to +5 V through a 4.7-k
Ω
resistor. The input
and output ratings and timing specifications for the Am9513A signals are given below.
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