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Services Power Management Unit
Copyright © 12/13/06 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006
Document Classification: Proprietary Information
Page 209
Not approved by Document Control. For review only.
8.7.2.4.6
Preparation for S3 State
Take the following steps if entering S3 state from S0 state:
•
If VCC_MEM is removed anytime while in S3 state, SDCKE must be maintained low using external logic
to ensure SDRAM contents are maintained during S3 state.
•
The application core software writes the Wake-up registers to enable the wake-up sources for S3 mode,
“Power Manager Wake-Up Enable Register (PWER)”
•
The application core software writes to disable any peripheral controller requiring special configuration in
S3. For example, disable the LCD controller during S3 when an external LCD panel with a built-in frame
buffer is used.
•
The application core software writes to the application core PWRMODE register (CP14 Register 7) to
request application subsystem S3 state entry.
•
Write an interrupt-handler routine for the application core to perform the necessary system operations and
software entry into S3 state if the nBATT_FAULT signal is asserted and the BIE bit in the
Management Unit Control Register (PMCR)”
is set. If the PCMR[BIE] bit is set, an assertion of
nBATT_FAULT causes an interrupt. If the PCMR[BIE] bit is clear, an assertion of the nBATT_FAULT
causes an automatic entry into S3 state.
Typically, the interrupt handler routine preserves critical application core cache and other critical information
before writing the application core PWRMODE register (CP14 Register 7). Depending on the design of the
external regulator system and how much time the regulator can continue to supply power after the assertion of
nBATT_FAULT, other action, such as completion of current routines, can also occur.
In some cases, such as S3 state with some units programmed to retain states, the latency of wake-up and the
interrupt-handler routine is longer than the external regulator can supply power once the nBATT_FAULT signals
are asserted. Clear the PCMR[BIE] bit in these cases.
8.7.2.4.7
Entering S3 State through Software Control
Entry into S3 state is initiated by setting the mode bits in the application core PWRMODE register (CP14
Register 7) to S3 state. S3 state entry through software control includes setting the mode bits to S3 when
nBATT_FAULT is asserted with PCMR[BIE] = 1. In this case, nBATT_FAULT assertion generates an interrupt
to the application core, enabling the core to enter S3 state through software control.
Note:
If the current S3 entry is due to nBATT_FAULT assertion with PMCR[BIE=1], software must
write a value of 0xF to the PWER register before writig to the PWRMODE register. This is done
to allow software to have a known value in this register before entering S3 due to a battery fault.
When the PWRMODE bits are written, the BPMU transitions the application subsystem to D4 mode and then the
MPMU transitions the rest of the processor architecture to S3 state. To complete S3 state entry, the MPMU
completes the following:
1. The MPMU disables the core and system PLLs.
2. The MPMU disables the processor oscillator.