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Deep Sleep Mode
9.9
Deep Sleep Mode
This device supports a Deep Sleep mode where all device clocks are stopped and the on-chip oscillator is
shut down to save power. Registers and memory contents are preserved, thus, upon recovery, the
program may continue from where it left off with minimal overhead involved.
The Deep Sleep mode is initiated when the DEEPSLEEP pin is driven low. The device wakes up from
Deep Sleep mode when the DEEPSLEEP pin is driven high. The DEEPSLEEP pin can be driven by an
external controller or it can be driven internally by the real-time clock (RTC). The RTC method allows for
automatic wake-up at a programmed time.
9.9.1 Entering/Exiting Deep Sleep Mode Using Externally Controlled Wake-Up
9.9.1.1
Entering Deep Sleep Mode
Use the following procedure to enter the Deep Sleep mode if an external signal is used to wake-up the
device:
1. To preserve DDR2/mDDR memory contents, activate the self-refresh mode and gate the clocks to the
DDR2/mDDR memory controller. You can use partial array self-refresh (PASR) for additional power
savings for mDDR memory.
2. The USB2.0 (USB0) PHY should be disabled, if this interface is used and internal clocks are selected
(see
).
3. PLL/PLLC0 and PLL/PLLC1 should be placed in bypass mode (clear the PLLEN bit in the PLL control
register (PLLCTL) of each PLLC to 0).
4. PLL/PLLC0 and PLL/PLLC1 should be powered down (set the PLLPWRDN bit in PLLCTL of each
PLLC to 1).
5. Configure the DEEPSLEEP pin as input-only using the PINMUX0_31_28 bits in the PINMUX0 register.
6. The external controller should drive the DEEPSLEEP pin high (not in Deep Sleep).
7. Configure the desired delay in the SLEEPCOUNT bit field in the deep sleep register (DEEPSLEEP) in
the System Configuration Module. This count determines the delay before the Deep Sleep logic
releases the clocks to the device during wake up (allowing the oscillator to stabilize).
8. Set the SLEEPENABLE bit in DEEPSLEEP to 1. This automatically clears the SLEEPCOMPLETE bit.
9. Begin polling the SLEEPCOMPLETE bit until it is set to 1. This bit is set once the device is woken up
from Deep Sleep mode.
10. The external controller drives the DEEPSLEEP pin low to initiate Deep Sleep mode.
For more details on the clock stop procedure of the DDR2/mDDR memory controller, see the
AM17x/AM18x ARM Microprocessor DDR2/mDDR Memory Controller User's Guide (
9.9.1.2
Exiting Deep Sleep Mode
Use the following procedure to exit the Deep Sleep state if an external signal is used to wake-up the
device:
1. The external controller drives the DEEPSLEEP pin high.
2. When the SLEEPCOUNT delay is complete, the Deep Sleep logic releases the clock to the device and
sets the SLEEPCOMPLETE bit in the deep sleep register (DEEPSLEEP) in the System Configuration
Module.
3. Clear the SLEEPENABLE bit in DEEPSLEEP to 0. This automatically clears the SLEEPCOMPLETE
bit.
4. Initialize the PLL controllers as described in
. Note that the state of the PLL controller
registers is preserved during Deep Sleep mode. Therefore, it is not necessary to reprogram all the PLL
controller registers unless a new setting is desired. At minimum, steps 3, 4, and 7-10 of the PLL
initialization procedure must be followed.
5. Enable the clocks to the DDR2/mDDR memory controller, reset the DDR PHY, and then take the
DDR2/mDDR out of self-refresh mode.
6. Configure the desired states to the peripherals and enable as required.
139
SPRUGX5A
–
May 2011
Power Management
Copyright
©
2011, Texas Instruments Incorporated
Содержание AM1802
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