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Slave Clock Control Unit
Copyright © 12/13/06 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006
Document Classification: Proprietary Information
Page 159
Not approved by Document Control. For review only.
7.2.4.3
Entering D0CS Mode
Enter D0CS mode as follows:
•
Set D0 mode Clock Select (D0CS) bit in the
“Application Subsystem Clock Configuration Register
register.
•
Write 0x5 to the lower three bits of Section 7.5.16, “Application Core PWRMODE Register (CP14 Register
7)” on page 7-61.
Warning 1: The BPMU performs a full-system drain as it would for a normal power-mode entry, and then
transitions the system clocks to the ring oscillator-based frequencies. The part may hang in an
unrecoverable manner if the core is not at the lowest frequency. Change the core frequency to its
lowest frequency before entering D0CS mode.
Warning 2: Wait 100 ms after the D0CS status bit in the
“Application Subsystem Clock Status Register
is set to clear the SPDIS bit in the
“Application Subsystem Clock Configuration
7.2.4.4
Exiting D0CS Mode
Exit D0CS mode as follows:
•
Set D0 mode Clock Select (D0CS) bit in the
“Application Subsystem Clock Configuration Register
register to 0.
•
Write 0x5 to the lower three bits of Section 7.5.16, “Application Core PWRMODE Register (CP14 Register
7)” on page 7-61.
The BPMU performs a full-system drain as it would for a normal power-mode entry, and then transitions the
system clocks to the PLL-based frequencies.
Warning:
The part may hang in an unrecoverable manner if the PLLs were not enabled prior to this
operation. PLL states are accessed by SPDIS and XPDIS bits in the
Clock Configuration Register (ACCR)”
.
7.2.4.5
CP14 Commands While in D0CS
Software can use the Coprocessor 14 interface to issue commands to the BCCU while the part is fully in D0CS
mode of operation; that is, all components of the D0CS entry sequence—including any PMIC sequences—have
completed. These commands are discussed briefly in the following paragraphs:
•
A low-power mode (D1, D2, etc...) entry command - the PXA300 processor behaves just as if the command
were issued in PLL run mode (D0). Upon exit from the low-power mode, the processor returns to D0CS
mode. The clocks are not switched over to PLL source even if the PLLs are enabled. The state of the PLLs
(enabled/disabled) is determined exclusively by the state of the XPDIS and SPDIS bits in
, when in run mode (either D0 or D0CS).
•
A core idle mode operation - the PXA300 processor enters the idle mode of operation just as it does in PLL
run mode (D0). The processor returns to D0CS mode of operation when an interrupt occurs.
•
Another D0CS entry or exit sequence - A second entry into D0CS while already in that mode is meaningless
and is ignored. Software is allowed to proceed but with no state change. An exit sequence takes the PXA300
processor out of D0CS and places it in regular PLL run mode (D0).