Analog Devices ADSP-BF59x Blackfin Hardware Reference Manual page 220

Dynamic Power Management Controller
Unlike other Blackfin derivatives that feature an internal voltage regulator;
the voltage level for the ADSP-BF59x cannot be changed by program-
ming the
VR_CTL
would automatically enter the active mode when the processor enters the
state. At that point the voltage level would change and the PLL
IDLE
would re-lock to the new voltage. After the
part returns to the full-on state.
With an external voltage regulator, this sequence must be reproduced in
the program code by the user. The
this case, but the value is still needed for calculating the required delay. A
larger
PLL_LOCKCNT
when changing just the PLL frequency. See the processor data sheet for
details.
The processor must enter active mode before the user can access the exter-
nal voltage regulator and program a new voltage level. See the data sheet of
external voltage regulator for information on changing voltage levels. See
the processor data sheet for more information about voltage tolerances
and allowed rates of change.

Reducing the processor's operating voltage to greatly conserve
power or raising the operating voltage to greatly increase perfor-
mance will probably require significant changes to the operating
voltage level. To ensure predictable behavior the recommended
procedure is to bring the processor to the sleep operating mode
before substantially varying the voltage.
The user must ensure a stable voltage and give the PLL time to re-lock at
the new voltage level. This can be done by running the core in a loop for a
certain amount of time before leaving active mode.
After the voltage has been changed to the new level, the processor can
safely return to any operational mode—so long as the operating parame-
ters, such as core clock frequency (CCLK), are within the limits specified
in the processor data sheet for the new operating voltage level.
6-16
register. With an internal voltage regulator, the PLL
PLL_LOCKCNT
value may be necessary for changing voltages than
ADSP-BF59x Blackfin Processor Hardware Reference
has expired, the
PLL_LOCKCNT
register cannot be used in