9.3.5 RESETn Pin Reset
The pin reset on EFR32 can be configured to be either hard or soft. By default, pin reset is configured as a soft reset source. To config-
ure it as a hard reset, clear the PINRESETSOFT bit in CLW0 in the Lock bit page, see
7.3.2 Lock Bits (LB) Page Description
Forcing the RESETn pin low generates a reset of the EFR32. The RESETn pin includes an on-chip pull-up resistor, and can therefore
be left unconnected if no external reset source is needed. Also connected to the RESETn line is a filter which prevents glitches from
resetting the EFR32.
9.3.6 Watchdog Reset
The Watchdog circuit is a timer which (when enabled) must be cleared by software regularly. If software does not clear it, a Watchdog
reset is activated. This functionality provides recovery from a software stalemate. Refer to the Watchdog section for specifications and
description. The Watchdog reset can be configured to cause different levels of reset as determined by WDOGRMODE in the
RMU_CTRL register.
9.3.7 Lockup Reset
A Cortex-M4 lockup is the result of the core being locked up because of an unrecoverable exception following the activation of the pro-
cessor’s built-in system state protection hardware.
A Cortex-M4 lockup gives immediate indication of seriously errant kernel software. This is the result of the core being locked up due to
an unrecoverable exception following the activation of the processor’s built in system state protection hardware. For more information
about the Cortex-M4 lockup conditions see the ARMv7-M Architecture Reference Manual. The Lockup reset does not reset the Debug
Interface, unless configured as a FULL reset. The Lockup reset can be configured to cause different levels of reset as determined by
the LOCKUPRMODE bits in the RMU_CTRL register. This includes disabling the reset.
9.3.8 System Reset Request
Software may initiate a reset (e.g. if it finds itself in a non-recoverable state). By asserting the SYSRESETREQ in the Application Inter-
rupt and Reset Control Register, a reset is issued. The SYSRESETREQ does not reset the Debug Interface, unless configured as a
FULL reset. The SYSRESTREQ reset can be configured to cause different levels of reset as determined by SYSRESETRMODE bits in
the RMU_CTRL register. This includes disabling the reset.
9.3.9 Reset State
The RESETSTATE bitfield in RMU_CTRL is a read-write register intended for software use only, and can be used to keep track of state
throughout a reset. This bitfield is only reset by POR and hard pin reset.
9.3.10 Register Reset Signals
Figure 9.1 RMU Reset Input Sources and Connections on page 200
shows an overview of how the different parts of the design are
affected by the different levels of reset. For RMU, EMU and CMU there are some exceptions. These are given in the following tables.
Reference Manual
RMU - Reset Management Unit
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