ADLINK DAQe-2502 - Manual (Page 57)

Operation Theory 47
General Purpose Timer/Counter Modes
Eight programmable timer/counter modes are provided. All modes
start operations following the software start command. The GPTC
software reset command initializes the status of the counter and
re-loads the initial value to the counter.
Mode1: Simple Gated-Event Counting
The counter counts the number of pulses on the GPTC_CLK
after the software start. Initial count value can be loaded via
software. Current count value can be read-back by software at
anytime. GPTC_GATE is used to enable/disable counting.
When GPTC_GATE is inactive, the counter halts the current
count value. Figure 4-17 illustrates the operation with initial
count = 5 in down-counting mode.
Figure 4-17: Mode1 Operation
Mode2: Single Period Measurement
The counter counts the period of the signal on GPTC_GATE in
terms of GPTC_CLK. Initial count can be loaded via 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 measure-
ment, GPTC_OUT outputs high and current count value can be
read-back by software. Figure 4-18 illustrates the operation
where initial count = 0, up-counting mode.