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Modes of Operation
15-26
ADSP-BF537 Blackfin Processor Hardware Reference
Pulse Width Count and Capture (WDTH_CAP) Mode
Use the
WDTH_CAP
mode, often simply called “capture mode,” to measure
pulse widths on the
TMRx
or
TACIx
input pins, or to “receive” PWM sig-
nals.
shows a flow diagram for
WDTH_CAP
mode.
In
WDTH_CAP
mode, the
TMRx
pin is an input pin. The internally clocked
timer is used to determine the period and pulse width of externally applied
rectangular waveforms. Setting the
TMODE
field to b#10 in the
TIMERx_CONFIG
register enables this mode.
When enabled in this mode, the timer resets the count in the
TIMERx_COUNTER
register to 0x0000 0001 and does not start counting until
it detects a leading edge on the
TMRx
pin.
When the timer detects the first leading edge, it starts incrementing.
When it detects a trailing edge of a waveform, the timer captures the cur-
rent 32-bit value of the
TIMERx_COUNTER
register into the width buffer
register. At the next leading edge, the timer transfers the current 32-bit
value of the
TIMERx_COUNTER
register into the period buffer register. The
count register is reset to 0x0000 0001 again, and the timer continues
counting and capturing until it is disabled.
In this mode, software can measure both the pulse width and the pulse
period of a waveform. To control the definition of leading edge and trail-
ing edge of the
TMRx
pin, the
PULSE_HI
bit in the
TIMERx_CONFIG
register is
set or cleared. If the
PULSE_HI
bit is cleared, the measurement is initiated
by a falling edge, the content of the counter register is captured to the
pulse width buffer on the rising edge, and to the period buffer on the next
falling edge. When the
PULSE_HI
bit is set, the measurement is initiated by
a rising edge, the counter value is captured to the pulse width buffer on
the falling edge, and to the period buffer on the next rising edge.
Содержание Blackfin ADSP-BF537
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Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...