Analog Devices ADSP-BF506F Hardware Reference Manual page 450

Modes of Operation
The current timer counter value is always copied to the width buffer and
period buffer registers at the trailing and leading edges of the input signal,
respectively, but these values are not visible to software. A measurement
report event samples the captured values into visible registers and sets the
timer interrupt to signal that
be read. When the
just after the period buffer captures its value (at a leading edge). When the
bit is cleared, the measurement report occurs just after the
PERIOD_CNT
width buffer captures its value (at a trailing edge).
If the
PERIOD_CNT
then the
TIMER_PERIOD
and pulse width measured in the period that just ended. If the
bit is cleared and a trailing edge occurred (see
register reports the pulse width measured in the pulse that
TIMER_WIDTH
just ended, but the
sured at the end of the previous period.
If the
PERIOD_CNT
the first period value has not yet been measured at the first measurement
report, so the period value is not valid. Reading the
this case returns "0", as shown in
width of a waveform that has only one leading edge and one trailing edge,
set
PERIOD_CNT
tured in the period buffer. Instead, an error report interrupt is generated
(if enabled) when the counter range is exceeded and the counter wraps
around. In this case, both
(because no measurement report occurred to copy the value captured in
the width buffer to
10-26
TIMER_PERIOD
bit is set, the measurement report occurs
PERIOD_CNT
bit is set and a leading edge occurred (see
and
TIMER_WIDTH
TIMER_PERIOD
bit is cleared and the first trailing edge occurred, then
= 0. If
PERIOD_CNT
TIMER_WIDTH
). See the first interrupt in
TIMER_WIDTH
ADSP-BF50x Blackfin Processor Hardware Reference
and
TIMER_WIDTH
registers report the pulse period
Figure
register reports the pulse period mea-
TIMER_PERIOD
Figure 10-12. To measure the pulse
= 1 for this case, no period value is cap-
and
TIMER_PERIOD
are ready to
Figure 10-11),
PERIOD_CNT
10-12), then the
value in
read "0"
Figure 10-13.