ADLINK PXI-2022 - Manual (Page 52)

44 Function Block and Operation Theory
4.8.2 General Purpose Timer/Counter Modes
Eight programmable timer/counter modes are provided. All modes
start operating following a software-start signal that is set by the
software. The GPTC software reset initializes the status of the
counter and re-loads the initial value to the counter. The operation
remains halted until the soft-ware-start is re-executed. The operat-
ing theories under different modes are described as below.
Mode 1: 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 4-16 illus-
trates the operation with initial count = 5, count-down mode.
Figure 4-16: Mode 1 Operation
5 5 4 3 2 1 1 0 ffff
Gate
CLK
Count value
Software start