TM4C1231H6PM Datasheet, PDF (468/1146 Pages) Texas Instruments – Tiva™ TM4C1231H6PM Microcontroller

Hibernation Module
7.4
7.4.1
after waking from hibernation to see if a wake condition was caused by one of the events above or
by a power loss.
The WAKE pin can generate interrupts in Run, Sleep and Deep Sleep Mode. The events that can
trigger an interrupt are configured by setting the appropriate bits in the Hibernation Interrupt Mask
(HIBIM) register. Pending interrupts can be cleared by writing the corresponding bit in the Hibernation
Interrupt Clear (HIBIC) register.
Initialization and Configuration
The Hibernation module has several different configurations. The following sections show the
recommended programming sequence for various scenarios. Because the Hibernation module runs
at a low frequency and is asynchronous to the rest of the microcontroller, which is run off the system
clock, software must allow a delay of t_{HIB_REG_ACCESS} after writes to registers (see “Register Access
Timing” on page 460). The WC interrupt in the HIBMIS register can be used to notify the application
when the Hibernation modules registers can be accessed.
Initialization
The Hibernation module comes out of reset with the system clock enabled to the module, but if the
system clock to the module has been disabled, then it must be re-enabled, even if the RTC feature
is not used. See page 324.
If a 32.768-kHz crystal is used as the Hibernation module clock source, perform the following steps:
1. Write 0x0000.0010 to the HIBIM register to enable the WC interrupt.
2. Write 0x40 to the HIBCTL register at offset 0x10 to enable the oscillator input.
3. Wait until the WC interrupt in the HIBMIS register has been triggered before performing any other
operations with the Hibernation module.
If a 32.768-kHz single-ended oscillator is used as the Hibernation module clock source, then perform
the following steps:
1. Write 0x0000.0010 to the HIBIM register to enable the WC interrupt.
2. Write 0x0001.0040 to the HIBCTL register at offset 0x10 to enable the oscillator input and
bypass the on-chip oscillator.
3. Wait until the WC interrupt in the HIBMIS register has been triggered before performing any other
operations with the Hibernation module.
The above steps are only necessary when the entire system is initialized for the first time. If the
microcontroller has been in hibernation, then the Hibernation module has already been powered
up and the above steps are not necessary. The software can detect that the Hibernation module
and clock are already powered by examining the CLK32EN bit of the HIBCTL register.
Table 7-2 on page 468 illustrates how the clocks function with various bit setting both in normal
operation and in hibernation.
Table 7-2. Hibernation Module Clock Operation
CLK32EN PINWEN RTCWEN RTCEN Result Normal Operation Result Hibernation
0
X
X
X Hibernation module disabled Hibernation module disabled
1
0
0
1 RTC match capability enabled. No hibernation
468
June 12, 2014
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