ADLINK PXI-2502 - Manual (Page 46)

38
• Operation Theoreym
4.4.2.1 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 value can be loaded via software.
Current count value can be read-back by software at any time.
GPTC_GATE is used to enable/disable counting. When GPTC_GATE is
inactive, the counter halts the current count value. Figure 4.4.1 illustrates
the operation with initial count = 5 in down-counting mode.
5 5 4 3 2 1 1 0 ffff
Gate
CLK
Count value
Software start
Figure 4.4.1 Mode 1 Operation
4.4.2.2 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 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 com-
pletion of the period measurement, GPTC_OUT outputs high and current
count value can be read-back by software. Figure 4.4.2 illustrates the
operation where initial count = 0, up-counting mode.
0 0 1 2 3 4 5 5 5
Gate
CLK
Count value
Software start
Figure 4.4.2 Mode 2 Operation