LM4F110H5QR Datasheet, PDF (476/1155 Pages) Texas Instruments – Microcontroller

Hibernation Module
7.3.6
7.3.7
Table 7-2. Counter Behavior with a TRIM Value of 0x8003 (continued)
RTCC [6:0]
0x01
0x01
0x01
0x01
0x02
RTCSSC
0x7FFC
0x7FFD
0x7FFE
0x7FFF
0x0
In the case of a trim value below 0x7FFF, the RTCSSC value is advanced from 0x7FFF to the trim
value while the RTCC value is incremented from 0x0 to 0x1. If the match value is within that range,
the match interrupt is not triggered. For example, as shown in Table 7-3 on page 476, if the match
interrupt was configured with RTCM0=0x1 and RTCSSM=0x2,an interrupt would never be triggered.
Table 7-3. Counter Behavior with a TRIM Value of 0x7FFC
RTCC [6:0]
0x00
0x00
0x00
0x01
0x01
0x01
RTCSSC
0x7FFD
0x7FFE
0x7FFF
0x3
0x4
0x5
The RTC must be enabled with the RTCEN bit of the HIBCTL register. The RTC can be configured
to generate interrupts by using the interrupt registers (see “Interrupts and Status” on page 477). 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 16 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.
476
April 25, 2012
Texas Instruments-Advance Information