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PXA300 Processor and PXA310 Processor
Vol. I: System and Timer Configuration Developers Manual
Doc. No. MV-TBD-00 Rev. A
CONFIDENTIAL
Copyright © 12/13/06 Marvell
Page 216
Document Classification: Proprietary Information
December 13, 2006
Not approved by Document Control. For review only.
Note:
The ADTV1, SDTV1, and OVER1 are registers defined in the power-management integrated
circuit (PMIC) used to interface to the processor.
Note:
If no PMIC is included in the system or can not respond to the control registers as specified in
the PXA3xx Processor PMIC Application Note, the PWR_I
2
C will time-out and continue the
SOD sequence without completing the PWR_I
2
C commands.
8.8.3.2
Coupling Voltage Change with Application Subsystem Frequency
Change
An application-subsystem frequency change can be used to alter clock frequencies of processor
peripherals
including the application core frequency without affecting the frequency of other processor peripherals.
Application-subsystem frequency changes can be coupled with a voltage change to achieve optimum power
consumption. Changing VCC_APPS and VCC_SRAM voltages when changing application subsystem
frequencies may increase the time between frequency changes due to the additional time needed to modify the
voltage. Optimize power consumption vs. performance by using the MTS bits in the Application Subsystem
Power Status/Configuration register (ASCR) and the FVE bit in the
“Power Management Unit Voltage Change
.
Note:
When raising the application-subsystem peripheral frequencies, the voltage must be raised first
and then the clock switched to the selected higher frequency. Conversely, when lowering the
application-subsystem peripheral frequencies, the clock must first be switched to the new lower
frequency and then the voltage lowered.
Note:
When exiting reset, VCC_APPS and VCC_SRAM are set to the highest operating voltage.
Consequently, when executing the first an application-subsystem frequency change after reset,
the voltage-frequency change sequence will be different from other frequency change
operations. If the selected frequencies require the highest voltage level, no voltage-change
operation will occur. If the selected frequencies require a voltage other than the highest voltage
level, the voltage will be lowered first and then the clock switched to the selected higher
frequency.
Although the following examples list voltage changes coupled with application core frequency changes, the
examples apply to all application-subsystem frequency-change operations, not just application core frequency
changes. Refer to
Chapter 6, “Services Clock Control Unit”
for more information on the application subsystem
peripherals that have selectable frequencies.
When the FVE bit in the
“Power Management Unit Voltage Change Control Register (PVCR)”
is set and an
application core PLL or programmable module frequency-change sequence is initiated by software, a
VCC_APPS and VCC_SRAM voltage-change sequence is initiated by the PWR_I
2
C if the current voltage is not
the required voltage. Software must perform the following to enact an application core PLL frequency change
with a VCC_APPS and VCC_SRAM
voltage change:
1. Set FVE to 1 by writing the
“Power Management Unit Voltage Change Control Register (PVCR)”
2. Set MTS in Application Subsystem Power Status/Configuration register (ASCR) to the maximum XN value
required by writing the ASCR.
3. Write to the ACCR, setting XL and XN to the required values.