
ADSP-BF59x Blackfin Processor Hardware Reference
8-21
General-Purpose Timers
Using PWM_OUT Mode With the PPI
Some timers may be used to generate frame sync signals for certain PPI
modes. For detailed instructions on how to configure the timers for use
with the PPI, refer to
“Frame Synchronization in GP Modes” on
page 15-19
.
Stopping the Timer in PWM_OUT Mode
In all
PWM_OUT
mode variants, the timer treats a disable operation (W1C to
TIMER_DISABLE
) as a “stop is pending” condition. When disabled, it auto-
matically completes the current waveform and then stops cleanly. This
prevents truncation of the current pulse and unwanted PWM patterns at
the
TMR
pin. The processor can determine when the timer stops running by
polling for the corresponding
TRUN
bit in the
TIMER_STATUS
register to read
"0" or by waiting for the last interrupt (if enabled). Note the timer cannot
be reconfigured (
TIMER_CONFIG
cannot be written to a new value) until
after the timer stops and
TRUN
reads "0".
In
PWM_OUT
single pulse mode (
PERIOD_CNT
= 0), it is not necessary to write
TIMER_DISABLE
to stop the timer. At the end of the pulse, the timer stops
automatically, the corresponding bit in
TIMER_ENABLE
(and
TIMER_DISABLE
) is cleared, and the corresponding
TRUN
bit is cleared. See
Figure 8-4 on page 8-13
. To generate multiple pulses, write a "1" to
TIMER_ENABLE
, wait for the timer to stop, then write another "1" to
TIMER_ENABLE
.
In continuous PWM generation mode (
PWM_OUT
,
PERIOD_CNT
= 1) software
can stop the timer by writing to the
TIMER_DISABLE
register. To prevent
the ongoing PWM pattern from being stopped in an unpredictable way,
the timer does not stop immediately when the corresponding "1" has been
written to the
TIMER_DISABLE
register. Rather, the write simply clears the
enable latch and the timer still completes the ongoing PWM patterns
gracefully. It stops cleanly at the end of the first period when the enable
latch is cleared. During this final period the
TIMEN
bit returns "0", but the
TRUN
bit still reads as a "1".
Содержание ADSP-BF59x Blackfin
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Страница 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
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Страница 244: ...Programming Examples 6 40 ADSP BF59x Blackfin Processor Hardware Reference...
Страница 345: ...ADSP BF59x Blackfin Processor Hardware Reference 9 9 Core Timer Unique Information for the ADSP BF59x Processor None...
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Страница 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...