
ADSP-BF59x Blackfin Processor Hardware Reference
8-43
General-Purpose Timers
Usage of the
TIMER_PERIOD
register, shown in
Figure 8-21
, and the
TIMER_WIDTH
register, shown in
Figure 8-22
, varies depending on the
mode of the timer:
• In PWM_OUT mode, both the TIMER_PERIOD and
TIMER_WIDTH register values can be updated “on-the-fly” since
the values change simultaneously.
• In WDTH_CAP mode, the timer period and timer pulse width
buffer values are captured at the appropriate time. The
TIMER_PERIOD and TIMER_WIDTH registers are then
updated simultaneously from their respective buffers. Both regis-
ters are read-only in this mode.
• In EXT_CLK mode, the TIMER_PERIOD register is writable and
can be updated “on-the-fly.” The TIMER_WIDTH register is not
used.
If new values are not written to the
TIMER_PERIOD
register or the
TIMER_WIDTH
register, the value from the previous period is reused. Writes
to the 32-bit
TIMER_PERIOD
register and
TIMER_WIDTH
register are atomic; it
is not possible for the high word to be written without the low word also
being written.
Values written to the
TIMER_PERIOD
registers or
TIMER_WIDTH
registers are
always stored in the buffer registers. Reads from the
TIMER_PERIOD
or
TIMER_WIDTH
registers always return the current, active value of period or
pulse width. Written values are not read back until they become active.
When the timer is enabled, they do not become active until after the
TIMER_PERIOD
and
TIMER_WIDTH
registers are updated from their respective
buffers at the end of the current period. See
Figure 8-1 on page 8-3
.
When the timer is disabled, writes to the buffer registers are immediately
copied through to the
TIMER_PERIOD
or
TIMER_WIDTH
register so that they
will be ready for use in the first timer period. For example, to change the
values for the
TIMER_PERIOD
and/or
TIMER_WIDTH
registers in order to use a
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 622: ...Unique Information for the ADSP BF59x Processor 15 38 ADSP BF59x Blackfin Processor Hardware Reference...
Страница 700: ...Programming Examples 16 78 ADSP BF59x Blackfin Processor Hardware Reference...
Страница 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...