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Datasheets and User Guides

App Notes

Software & Driver

 

2.5 - CNT

The input connection to the 32-bit counter is made at screw-terminal CNT. Internally there is a 1.5 kΩ series resistor (provides overvoltage protection) and then a 1 MΩ resistor to ground (weakly holds line low when floating).

The counter is incremented when it detects a falling edge followed by a rising edge. This means that if you reset the counter while your signal is low, you will not get the first count until it goes high-low-high. In situations where this first count is important, you should simply substract the initial count from the final count, rather than doing a reset.

The counter (CNT) is disabled when the watchdog is enabled.

Software

The functions ECount (easy function), AOUpdate, and Counter are used to reset or read the counter. If a reset is specified, the counter is read first. All of these functions take up to 20 ms to execute, providing a maximum update rate of about 50 Hz.

Counter readings can also be returned in stream mode (AIStreamRead) at up to 300 Hz.