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Slave Power Management Unit
Copyright © 12/13/06 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006
Document Classification: Proprietary Information
Page 241
Not approved by Document Control. For review only.
9.2.1.2.2
Preparation for GPIO Reset
When the BPMU is in D0 state, the BPMU has the additional task (as compared to other resets) of preserving
data integrity in the external DDR SDRAM memories. The actions the BPMU takes depend on the power state of
the PXA300 processor or PXA310 processor when the GPIO reset occurs. If the PXA300 processor or PXA310
processor is in a low power state before the GPIO reset occurs, the DDR SDRAM is already in self-refresh mode.
The cache and internal SRAM are not flushed if the GPIO reset occurs in S0/D0 mode.
Normal boot-up sequencing begins with all units in the application subsystem starting with their predefined reset
conditions. Core software must examine the
“Application Subsystem Reset Status Register (ARSR)”
to
determine if the reset source was a GPIO reset.
9.2.1.3
Low-Power State Exit Reset
Low-power state exit reset is invoked when the BPMU exits D4 power state. In low-power state exit reset, all
units in the application subsystem that were powered off are reset to their predefined reset states. Low-power
state exit reset is controlled by Master PMU (MPMU).
9.2.1.3.1
Behavior During Low-Power State Exit Reset
During low-power state exit reset, all units and pins in the application subsystem that were powered off while the
BPMU was in D4 power state are held in their predefined reset state.
9.2.1.4
Summary of Reset Sequences
The reset sequences on the application subsystem follow a similar sequence:
•
Reset to BPMU is de-asserted
•
BPMU requests entry to D0 state
•
BPMU de-asserts reset to application subsystem modules
•
ARSR register is written
•
Core reset reboot sequence begins
9.2.2
Power Management
The BPMU controls all internal application-subsystem power domains and requests external power-supply
functions from the MPMU as well as the enter and exit sequences of application- subsystem power states.
The BPMU controls:
•
All application-subsystem power domains except for the power domain powering the BPMU, clocks, OS
timers, mini-LCD, and mini-SRAM controller
•
Application-subsystem reset sequence except for reset of the BPMU
•
Application-subsystem wake-up events and power-state transitions for D0, D1, D2, and D3 power states
The power-management unit provides these three functions according to the current power state.
The BPMU power states are as follows: