LM3S2793 Datasheet, PDF (301/1194 Pages) Texas Instruments – Stellaris® LM3S2793 Microcontroller

Stellaris^® LM3S2793 Microcontroller
6.3.6
6.3.7
6.3.8
6.3.9
6.3.10
The Hibernation module includes two 32-bit match registers that are compared to the value of the
RTC counter. The match registers can be used to wake the processor from Hibernate mode or to
generate an interrupt to the processor if it is not in hibernation.
The RTC must be enabled with the RTCEN bit of the HIBCTL register. The value of the RTC can be
set at any time by writing to the HIBRTCLD register. The predivider trim can be adjusted by reading
and writing the HIBRTCT register. The predivider uses this register once every 64 seconds to adjust
the clock rate. The two match registers can be set by writing to the HIBRTCM0 and HIBRTCM1
registers. The RTC can be configured to generate interrupts by using the interrupt registers (see
“Interrupts and Status” on page 302). As long as the RTC is enabled and a valid V_BAT is present, the
RTC continues counting, regardless of whether V_DD is present or if the part is in hibernation.
Battery-Backed Memory
The Hibernation module contains 64 32-bit words of memory that are powered from the battery or
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. 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.
Power Control Using HIB
Important: 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_DC 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 regulator(s) 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
(which could be a battery or an auxiliary power source) 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.
Power Control Using VDD3ON Mode
The Hibernation module may also be configured to cut power to all internal modules. While in this
state, all pins are configured as inputs. In the VDD3ON mode, the regulator should maintain 3.3 V
power to the microcontroller during Hibernate. This power control mode is enabled by setting the
VDD3ON bit in HIBCTL.
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. If a Flash memory write operation is in progress when the HIBREQ bit is set, an
interlock feature holds off the transition into Hibernate mode until the write has completed.
Waking from Hibernate
The Hibernation module is configured to wake from the external WAKE pin by setting the PINWEN
bit of the HIBCTL register. It is configured to wake from RTC match by setting the RTCWEN bit. Note
that the WAKE pin uses the Hibernation module's internal power supply as the logic 1 reference.
January 20, 2012
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