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Additional Peripheral Power Management Considerations
9.9.4 Entering/Exiting Deep Sleep Mode Using Software Handshaking
Entering the Deep Sleep mode stops all of the clocks to the device so it is the responsibility of the
software to ensure that all peripheral accesses have been completed and peripheral interfaces
appropriately configured for clocks to stop. Therefore, before an external controller drives the
DEESPLEEP pin, a handshaking mechanism must be in place to give software time to prepare the device
for Deep Sleep mode. The implementation of the handshake mechanism is up to the system designer.
9.9.4.1
Entering Deep Sleep Mode
The following example sequence can be used to activate the Deep Sleep mode using a handshaking
mechanism between your device and an external device:
1. Clear the SLEEPENABLE bit in the deep sleep register (DEEPSLEEP) in the System Configuration
Module to 0. The DEEPSLEEP pin has no effect until software running on the device sets this bit.
2. Configure the GP0[8]/DEEPSLEEP/RTC_ALARM pin to output GP0[8] using the PINMUX0_31_28 bits
in the PINMUX0 register. When the pin is configured for GPIO functionality, the internal DEEPSLEEP
signal is still driven by the value on the pin.
3. Configure the GP0[8] pin to generate interrupts on the falling edge of the GPIO signal.
4. An external device drives the GP0[8] pin low.
5. Software prepares the device for Deep Sleep mode.
6. Set the SLEEPENABLE bit in DEEPSLEEP to 1. The Deep Sleep mode is immediately started and all
device clocks are stopped. Also, the SLEEPCOMPLETE bit is automatically cleared.
9.9.4.2
Exiting Deep Sleep Mode
To exit the Deep Sleep mode, follow this sequence:
1. An external device drives the GP0[8] pin high.
2. The device exits the Deep Sleep mode. 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.
9.10 Additional Peripheral Power Management Considerations
This section lists additional power management features and considerations that might be part of other
chip-level or peripheral logic, apart from the features supported by the core, PLL controller (PLLC), and
power and sleep controller (PSC).
9.10.1 USB PHY Power Down Control
The USB modules can be clock gated using the PSC; however, this does not power down/clock gate the
PHY logic. You can put the USB2.0 PHY and OTG module in the lowest power state, when not in use, by
writing to the USB0PHYPWDN and the USB0OTGPWRDN bits in the chip configuration 2 register
(CFGCHIP2) of the system configuration (SYSCFG) module.
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Power Management
SPRUGX5A
–
May 2011
Copyright
©
2011, Texas Instruments Incorporated
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