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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 146
Document Classification: Proprietary Information
December 13, 2006
Not approved by Document Control. For review only.
6.4.4
Timekeeping Oscillator (32.768 kHz)
The timekeeping oscillator is a low-power, low-frequency oscillator that clocks the real-time clock and power
manager. The timekeeping oscillator is always enabled; the CLK_TOUT signal can be used to drive a buffered
version of the TXTAL_IN pin and can be enabled using the TENS3, TENS2 and TENS0 bits in the
Configuration Register (OSCC)”
. By default, CLK_TOUT is enabled in S0 mode, which includes power-on and
hardware reset. See
for more information on the operation of CLK_TOUT.
For lowest power consumption, a 32.768-kHz crystal must be connected between the TXTAL_IN and
TXTAL_OUT pins. However, some applications may have other clock sources of the same frequency, and can
reduce overall cost by driving the PXA300 processor or PXA310 processor TXTAL_IN pin externally while
grounding the TXTAL_OUT pin.
6.4.5
Core Phase-Locked Loop (104–806 MHz)
The core PLL is the clock source for the core and switch logic within the application subsystem. Its output is not
used within the services unit. The core PLL generates two output frequencies—one for turbo mode and one for
run mode. These frequencies are:
•
Run-mode frequency = Processor (13-MHz) oscillator * XL
•
Turbo-mode frequency = Run-mode frequency * XN
The valid output-frequency selections are shown in . Note that the maximum specified frequency for the applied
VCC_APPS voltage must not be exceeded (see PXA300 Processor and PXA310 Processor Electrical,
Mechanical, and Thermal Specification for details).
The core PLL output frequency can be changed to optimize for power consumption and/or performance. During
the frequency change operation, the core PLL output is disabled while the core PLL relocks using the new values
of XL and XN.
The core PLL is enabled when the processor subsystem is in D0 power mode and is disabled in all other power
states.
6.4.5.1
High-Temperature Operation
The services unit PMU monitors the on-die temperature and reduces the operating frequency of the core PLL if
the temperature exceeds a specified operating range. For example, if the core PLL is programmed for XL = 31
and an on-die high-temperature condition is detected, the core PLL is changed to run with XL = 24. If the core
PLL was operating with XL = 12 and a high-temperature condition is detected, the core PLL is changed to run
with XL = 16. The high-temperature operation compensation can be disabled using the TD bit in the
Configuration Register (OSCC)”
.
6.4.6
System Phase-Locked Loop (624 MHz)
The system PLL creates a fixed-frequency clock used for generating many of the fixed-frequency clocks in the
application subsystem. The system PLL output clock is not used within the services unit.
The system PLL is enabled when requested by the application subsystem in D0 mode. The system PLL is
disabled at all other times. Refer to the “Slave Power Management Unit” chapter for more information on the D0
power mode.