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Functional Description
488
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Hibernation Module
6.3.7 Battery-Backed Memory
The Hibernation module contains 16 32-bit words of memory that are powered from the battery or an
auxiliary power supply and therefore retained during hibernation. The processor software can save state
information in this memory prior to hibernation and recover the state upon waking. To access the upper
eight words of memory, the processor must be in privilege mode. Refer to
for more
information about processor privilege mode. The battery-backed memory can be accessed through the
HIBDATA registers. If both V
DD
and V
BAT
are removed, the contents of the HIBDATA registers are not
retained.
6.3.8 Power Control Using HIB
NOTE:
The Hibernation Module requires special system implementation considerations when using
HIB to control power, as it is intended to power-down all other sections of the microcontroller.
All system signals and power supplies that connect to the chip must be driven to 0 V or
powered down with the same regulator controlled by HIB.
The Hibernation module controls power to the microcontroller through the use of the HIB pin which is
intended to be connected to the enable signal of the external regulators providing 3.3 V to the
microcontroller and other circuits. When the HIB signal is asserted by the Hibernation module, the external
regulator is turned off and no longer powers the microcontroller and any parts of the system that are
powered by the regulator. The Hibernation module remains powered from the V
BAT
supply until a Wake
event. Power to the microcontroller is restored by deasserting the HIB signal, which causes the external
regulator to turn power back on to the chip.
6.3.9 Power Control Using VDD3ON Mode
The Hibernation module may also be configured to cut power to all internal modules during Hibernate
mode. While in this state, if VDD3ON is set in the HIBCTL register, all pins are held in the state they were
in prior to entering hibernation. For example, inputs remain inputs; outputs driven high remain driven high,
and so on. There are important procedural and functional items to note when in VDD3ON mode:
•
JTAG Ports C[0] - C[3] do not retain their state in Hibernate VDD3ON mode.
•
If GPIO pins K[7:4] are not used as a wake source, they should not be left floating. An internal pullup
resistor may be configured by the application before entering Hibernate mode by programming the
GPIO Pull-Up Select (GPIOPUR) register in the GPIO module.
•
In the VDD3ON mode, the regulator should maintain 3.3 V power to the microcontroller during
Hibernate. GPIO retention is disabled when the RETCLR bit is cleared in the HIBCTL register.
•
When entering hibernation in VDD3ON mode, the supply rails to the Ethernet resistors R1, R2, R3, R4
found in
must be switched off.
6.3.10 Initiating Hibernate
Hibernate mode is initiated when the HIBREQ bit of the HIBCTL register is set. If a wake-up condition has
not been configured using the PINWEN or RTCWEN bits in the HIBCTL register, the hibernation request
is ignored. In addition, if the battery voltage is below the threshold voltage defined by the VBATSEL field
in the HIBCTL register, the hibernation request is ignored.
6.3.11 Waking from Hibernate
The Hibernation module can be configured to wake from Hibernate mode if any of the following are
enabled:
•
External WAKE
•
External RST
•
GPIO K[7:4]
•
Tamper TMPR[3:0]
•
Tamper XOSC failure