To characterize the frequency of a
single waveform, WADI counts the number of edges in the prefixed time window set by
the SIGxEDGECFG register. To use the edge counter, the SIGxEDGECFG[CNTEN] bit must
be set.
- The time window within which the
edges are counted is defined with the SIGxEDGECFG[TIMEWNDOW]. The window size is
in terms of SYSCLK in which the edges are counted. The time window starts upon
event of the configured trigger (start of edge counting) and ends upon lapse of
configured window length (edge counting is stopped). The count begins on the
edge defined by SIGxCFG[SIGPOL].
- The SIGxCFG[SIGPOL] is useful to
start counting specific edge. While SIGxCFG[EDGE_SPAN] allows skipping
intermediate edges. For frequency or edge count measurement, the recommended
configuration for SIGxCFG[EDGE_SPAN] is 0x2. This captures the second edge from
the previous edge detected, which counts the same edge type (that is, rise edge
to next rise edge) and measures the frequency of the waveform in the time
window. If the SIGxCFG[EDGE_SPAN] is configured greater than 2, then edges
counted accordingly skipping intermediate edges.