Timer Modes
16-16
ADSP-BF535 Blackfin Processor Hardware Reference
In PWM_OUT, the counter is reloaded at the end of every period
as well as at the end of every pulse. The generated waveform
depends on whether
TIMERx_WIDTH_LO
is updated before or after the
pulse width expires, due to the reload sequence described in
“Pulse
Width Modulation Mode (PWM_OUT)” on page 16-13
.
Changing the pulse width while the timer is running is typically accom-
plished by having an interrupt service routine write new values to the
width registers. As seen in
Figure 16-9
, this causes the generation of one
incorrect period if the write to the
TIMERx_WIDTH_LO
register occurs before
the ongoing pulse width expires. This is very likely because the interrupt is
requested at the end of a period.
If an application forbids single misaligned PWM patterns, the procedure
illustrated in
Figure 16-10
can be used. It alters the period value tempo-
rarily and restores the original period value the very next PWM cycle in
order to obtain constant PWM periods.
Figure 16-9. Possible Period Failure Due to Width Update with Timer
Running
W idt h
O ld
Per io d
W ro ng
Pe r iod
Pe r io d
W idt h
O ld
W idt h
N e w
W idt h
N ew
P e rio d -
W idt h O ld
P e r iod -
W idt h N e w
P e riod -
W idth Ne w
W ID TH = W idth N ew
Содержание ADSP-BF535 Blackfin
Страница 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Страница 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 908: ...SDRAM Controller External Bus Interface Unit B 36 ADSP BF535 Blackfin Processor Hardware Reference...