5.2.2.9
HSSR Reset
The
Hardware System Service Request (HSSR)
register can be used to restore the device back
to factory settings. A successful write to the
Hardware System Service Request (HSSR)
register
initiates a system reset. The reset initialization process executes before examining the
HSSR
register
and processing the command. This register can only be accessed in privileged mode.
Before the return-to-factory settings routine has completed, a system reset sequence executes and
the
HSSR
bit in the
RESC
register is set. After the HSSR function has been processed, the
CDOFF
field in the
HSSR
register is written with the outcome of the function processing and another HSSR
system reset is executed. The
HSSR
bit can be cleared in the
RESC
register by writing a 0.
For more information regarding use of the
HSSR
register, refer to “Hardware System Service
5.2.3
Non-Maskable Interrupt
The microcontroller has multiple sources of non-maskable interrupt (NMI):
■ The assertion of the
NMI
signal.
■ A main oscillator verification error.
■ The
NMISET
bit in the
Interrupt Control and State (INTCTRL)
register in the Cortex
™
-M4F (see
■ The Watchdog module time-out interrupt when the
INTTYPE
bit in the
Watchdog Control
(WDTCTL)
register is set (see page 1034).
■ Tamper event (see “Hibernation Module” on page 531 for more information).
■ Any of the following BOR trigger events:
– V
DDA
under BOR setting
– V
DD
under BOR setting
Software must check the cause of the interrupt in the
NMI Cause (NMIC)
register in order to
distinguish among the sources.
5.2.3.1
NMI Pin
The NMI signal is an alternate function for the GPIO port pin(s) specified in Table 26-3 on page 1785.
The alternate function must be enabled in the GPIO for the signal to be used as an interrupt, as
described in “General-Purpose Input/Outputs (GPIOs)” on page 742. Note that enabling the NMI
alternate function requires the use of the GPIO lock and commit function, similar to the requirements
of the GPIO port pins associated with JTAG/SWD functionality, see page 784. The active sense of
the
NMI
signal is High; asserting the enabled
NMI
signal above V
IH
initiates the NMI interrupt
sequence.
5.2.3.2
Main Oscillator Verification Failure
The TM4C1294NCPDT microcontroller provides a main oscillator verification circuit that generates
an error condition if the oscillator is running too fast or too slow. If the main oscillator verification
circuit is enabled and a failure occurs, either a power-on reset is generated and control is transferred
to the NMI handler, or an interrupt is generated. The
MOSCIM
bit in the
MOSCCTL
register determines
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System Control