National Instruments 321645c-01

Chapter 2 Function Reference — CTR_Square

NI-DAQ FRM for PC Compatibles 2-112

National Instruments Corporation

When you use special gating (gateMode = 8), you can achieve gate-controlled pulse

generation. When the gate input is high, NI-DAQ uses period1 to generate the pulses. When

the gate input is low, NI-DAQ uses period2 to generate the pulses. If the output mode is TC

Toggled, the result is two 50% duty square waves of difference frequencies. If the output

mode is TC Pulse, the result is two pulse trains of different frequencies.

Figure 2-11. Square Wave Timing

Square Wave Generation Timing Considerations

There is an uncertainty associated with the beginning of square wave generation due to

counter synchronization. Square wave generation starts on the first timebase edge after

NI-DAQ applies the starting signal. The time between receipt of the starting signal and the

start of the square wave generation can be between 0 and 1 units of the timebase in duration.

You should not use edge gating with square wave generation. If you use edge gating,

thewaveform stops after period1 expires and then continues for one total period

(period2+peri od1) only after NI-DAQ applies another edge. For continuous square wave

generation, use level or no gating.

0 < sync period < 1

Timebase

Starting

Signal

TC Toggle

Output

TC Pulse

Output

units = timebase period

period2

period2-1period1-1

period1