ADLINK PXI-2208 - Manual (Page 78)

66 Operation Theory
Mode1: Simple Gated-Event Counting
In this mode, the counter counts the number of pulses on the
GPTC_CLK after the software-start. Initial count can be loaded
from software. Current count value can be read-back by soft-
ware any time without affecting the counting. GPTC_GATE is
used to enable/disable counting. When GPTC_GATE is inac-
tive, the counter halts the current count value. Figure 4-23 illus-
trates the operation with initial count = 5, countdown mode.
Figure 4-23: Mode1 Operation
Mode2: Single Period Measurement
In this mode, the counter counts the period of the signal on
GPTC_GATE in terms of GPTC_CLK. Initial count can be
loaded from software. After the software-start, the counter
counts the number of active edges on GPTC_CLK between
two active edges of GPTC_GATE. After the completion of the
period interval on GPTC_GATE, GPTC_OUT outputs high and
then current count value can be read-back by software.
Figure 4-24 illustrates the operation where initial count = 0,
count-up mode.