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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 160
Document Classification: Proprietary Information
December 13, 2006
Not approved by Document Control. For review only.
Warning:
A core clock frequency/turbo change operation is not allowed while in D0CS
7.2.4.6
Non-CP14 Commands While in D0CS
Aside from the coprocessor commands discussed in
Section 7.2.4.5, “CP14 Commands While in D0CS”
software can issue commands by writing to various control bits in the Application Subsystem Clock
Configuration Register. See
Section 7.3.1, “Application Subsystem Clock Configuration Register (ACCR)”
for
additional information.
Writing to the XPDIS and SPDIS bits enables or disables the respective PLLs. For details, see
. Updates to the various frequency-selection fields (see
) do not result in an immediate frequency change. Rather, these values are held
until the part exits D0CS and returns to PLL run mode (D0). At this point, the peripheral frequency-change
process is initiated, and the frequencies of these units are updated accordingly. Software must poll the
corresponding status-update fields in
Section 7.3.2, “Application Subsystem Clock Status Register (ACSR)”
register to determine when the frequency-change process has completed.
7.2.5
Ring Oscillator (40 MHz ± 5%) During D1 Mode
When running in D1 mode, the processor uses the 40 MHz ring oscillator as the primary clock source. In D1
mode, only the mini-LCD and SRAM controller are operational.
lists the frequencies for the modules
that are operational with the ring oscillator clock in D1 mode.
7.2.6
Functional Clock Gating
The BCCU clock-enable registers contain configuration bits that can enable/disable the clocks to individual units
within their respective subsystems. The clock-enable registers can be accessed by the core. The BCCU contains
two clock-enable registers:
“D0 Mode Clock Enable Register A (D0CKEN_A)”
and
. When the processor is in D0 power mode, the BCCU uses the CKEN bits found in
these two registers to enable/disable the clocks to individual units.
The CKEN bits override the clock-gating functionality that may be present in some modules and should be used
only when an entire module is not being used. After power-on or a hardware reset, any module that is not being
used must have software disable its clock. Furthermore, if a module is temporarily idle, but does not have
clock-gating functionality within the module, use the CKEN register to disable the unit clock.
The CKEN bits enable/disable only the functional clock inputs to each module. Consequently, when a module
clock is disabled, all register reads/writes to that module still function properly. Consult the module chapter for
further information.
Table 7-5. D1 Frequencies from Ring Oscillator
Module
Frequency
Internal SRAM and mini-SRAM controller
NOTE: Internal mini-SRAM controller configuration does not have to
be reprogrammed wnen used in D1 mode.
40 MHz
Mini-LCD
40 MHz
BPMU
40 MHz
OS Timers
40 MHz