ADSP-BF531/ADSP-BF532
These modes support ADC/DAC connections, as well as video
communication with hardware signaling. Many of the modes
support more than one level of frame synchronization. If
desired, a programmable delay can be inserted between asser-
tion of a frame sync and reception/transmission of data.
Hibernate Operating Mode—Maximum Static Power
Savings
The hibernate mode maximizes static power savings by dis-
abling the voltage and clocks to the processor core (CCLK) and
to all the synchronous peripherals (SCLK). The internal voltage
regulator for the processor can be shut off by writing b#00 to
the FREQ bits of the VR_CTL register. This disables both CCLK
and SCLK. Furthermore, it sets the internal power supply volt-
age (V
DDINT
) to 0 V to provide the lowest static power dissipation.
Any critical information stored internally (memory contents,
register contents, etc.) must be written to a nonvolatile storage
device prior to removing power if the processor state is to be
preserved. Since V
DDEXT
is still supplied in this mode, all of the
external pins three-state, unless otherwise specified. This allows
other devices that may be connected to the processor to have
power still applied without drawing unwanted current. The
internal supply regulator can be woken up either by a real-time
clock wakeup or by asserting the RESET pin.
DYNAMIC POWER MANAGEMENT
The ADSP-BF531/ADSP-BF532 processor provides five operat-
ing modes, each with a different performance/power profile. In
addition, dynamic power management provides the control
functions to dynamically alter the processor core supply voltage,
further reducing power dissipation. Control of clocking to each
of the ADSP-BF531/ADSP-BF532 processor peripherals also
reduces power consumption. See
for a summary of the
power settings for each mode.
Table 4. Power Domains
Power Domain
All internal logic, except RTC
RTC internal logic and crystal I/O
All other I/O
V
DD
Range
V
DDINT
V
DDRTC
V
DDEXT
Sleep Operating Mode—High Dynamic Power Savings
The sleep mode reduces dynamic power dissipation by disabling
the clock to the processor core (CCLK). The PLL and system
clock (SCLK), however, continue to operate in this mode. Typi-
cally an external event or RTC activity will wake up the
processor. When in the sleep mode, assertion of wakeup will
cause the processor to sense the value of the BYPASS bit in the
PLL control register (PLL_CTL). If BYPASS is disabled, the pro-
cessor will transition to the full-on mode. If BYPASS is enabled,
the processor will transition to the active mode.
When in the sleep mode, system DMA access to L1 memory is
not supported.
Full-On Operating Mode—Maximum Performance
In the full-on mode, the PLL is enabled and is not bypassed,
providing capability for maximum operational frequency. This
is the power-up default execution state in which maximum per-
formance can be achieved. The processor core and all enabled
peripherals run at full speed.
Active Operating Mode—Moderate Power Savings
In the active mode, the PLL is enabled but bypassed. Because the
PLL is bypassed, the processor’s core clock (CCLK) and system
clock (SCLK) run at the input clock (CLKIN) frequency. In this
mode, the CLKIN to CCLK multiplier ratio can be changed,
although the changes are not realized until the full-on mode is
entered. DMA access is available to appropriately configured L1
memories.
In the active mode, it is possible to disable the PLL through the
PLL control register (PLL_CTL). If disabled, the PLL must be
re-enabled before transitioning to the full-on or sleep modes.
Table 5. Power Settings
PLL
Mode
PLL
Bypassed
Full-On
Enabled No
Active
Enabled/ Yes
Disabled
Sleep
Enabled
Deep Sleep Disabled
Hibernate Disabled
Core
Clock
(CCLK)
Enabled
Enabled
System
Clock
Core
(SCLK)
Power
Enabled On
Enabled On
Deep Sleep Operating Mode—Maximum Dynamic Power
Savings
The deep sleep mode maximizes dynamic power savings by dis-
abling the clocks to the processor core (CCLK) and to all
synchronous peripherals (SCLK). Asynchronous peripherals,
such as the RTC, may still be running but will not be able to
access internal resources or external memory. This powered-
down mode can only be exited by assertion of the reset interrupt
(RESET) or by an asynchronous interrupt generated by the
RTC. When in deep sleep mode, an RTC asynchronous inter-
rupt causes the processor to transition to the active mode.
Assertion of RESET while in deep sleep mode causes the proces-
sor to transition to the full-on mode.
Power Savings
As shown in
the ADSP-BF531/ADSP-BF532 processor
supports three different power domains. The use of multiple
power domains maximizes flexibility, while maintaining com-
pliance with industry standards and conventions. By isolating
the internal logic of the ADSP-BF531/ADSP-BF532 processor
into its own power domain, separate from the RTC and other
I/O, the processor can take advantage of dynamic power man-
agement, without affecting the RTC or other I/O devices. There
are no sequencing requirements for the various power domains.
Disabled Enabled On
Disabled Disabled On
Disabled Disabled Off
Rev. D |
Page 12 of 60 |
August 2006
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