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M0A21/M0A23 Series
May 06, 2022
Page
106
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
(SYS_BODCTL[10:8]), chip will be reset. The BOD reset will control the chip in reset state until the AV
DD
voltage rises above V
BOD
and the state keeps longer than De-glitch time set by BODDGSEL. The default
value of BODEN, BODVL and BODRSTEN (SYS_BODCTL[3]) is set by Flash controller user
configuration
register
CBODEN
(CONFIG0
[19]),
CBOV
(CONFIG0
[23:21])
and
CBORST(CONFIG0[20]) respectively. User can determine the initial BOD setting by setting the
CONFIG0 register. Figure 6.2-6 shows the Brown-out Detector waveform.
AV
DD
V
BODL
BODOUT
BODRSTEN
Brown-out
Reset
T
1
(< BODDGSEL)
T
2
(= BODDGSEL)
T
3
(= BODDGSEL)
Hysteresis
V
BODH
Figure 6.2-6 Brown-out Detector (BOD) Waveform
Watchdog Timer Reset (WDT)
In most industrial applications, system reliability is very important. To automatically recover the MCU
from failure status is one way to improve system reliability. The watchdog timer(WDT) is widely used to
check if the system works fine. If the MCU is crashed or out of control, it may cause the watchdog time-
out. User may decide to enable system reset during watchdog time-out to recover the system and take
action for the system crash/out-of-control after reset.
Software can check if the reset is caused by watchdog time-out to indicate the previous reset is a
watchdog reset and handle the failure of MCU after watchdog time-out reset by checking
WDTRF(SYS_RSTSTS[2]).
CPU Lockup Reset
CPU enters lockup status after CPU produces hardfault at hardfault handler and chip gives immediate
indication of seriously errant kernel software. This is the result of the CPU being locked because of an
unrecoverable exception followin
g the activation of the processor’s built in system state protection
hardware. When chip enters debug mode, the CPU lockup reset will be ignored.
CPU Reset, CHIP Reset and MCU Reset
The CPU Reset means only Cortex
®
-M0 core is reset and all other peripherals remain the same status
after CPU reset. User can set the CPURST(SYS_IPRST0[1]) to 1 to assert the CPU Reset signal.