Chapter 4
General-Purpose Counter/Timer
©
National Instruments Corporation
4-79
DAQ-STC Technical Reference Manual
4.8.11.9 Buffered Semiperiod Measurement
To use this function, set G_CONTROL conditioning to edge gating (double edge) and
program the counter to reload on G_CONTROL and generate interrupts on G_GATE. The
counter increments on every G_SOURCE rising edge following the ARM. Every G_GATE
transition is synchronized by the falling edge of G_SOURCE to generate a G_CONTROL
pulse. On the G_SOURCE rising edge following G_CONTROL, the counter reloads from the
selected load register. The HW save register switches to transparent mode on every edge of
G_GATE and returns to latched mode on the next G_SOURCE falling edge.
Figure 4-40 shows an example of buffered semiperiod measurement where the first
semiperiod is four G_SOURCE rising edges and the second semiperiod is three G_SOURCE
rising edges. The dotted line indicates where the ARM occurs and the arrows indicate where
the gate interrupt is generated.
Figure 4-40.
Buffered Semiperiod Measurement
Counter Value
Counter Load
G_SOURCE
G_GATE
G_CONTROL
HW Save
HW Save Register
2
1
3
1
2
3
4
1
2
3
1
2
3
4
3
