C8051F99X_10 Datasheet, PDF (183/322 Pages) Silicon Laboratories – Ultra Low Power, 8-2 kB Flash, Capacitive Sensing MCU

C8051F99x-C8051F98x
this bit reads 0. Writing a 1 to the MCDRSF bit enables the Missing Clock Detector; writing a 0 disables it.
The missing clock detector reset is automatically disabled when the device is in the low power suspend or
sleep mode. Upon exit from either low power state, the enabled/disabled state of this reset source is
restored to its previous value. The state of the RST pin is unaffected by this reset.
18.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a 1 to the C0RSEF flag (RSTSRC.5).
Comparator0 should be enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on
chatter on the output from generating an unwanted reset. The Comparator0 reset is active-low: if the non-
inverting input voltage (on CP0+) is less than the inverting input voltage (on CP0–), the device is put into
the reset state. After a Comparator0 reset, the C0RSEF flag (RSTSRC.5) will read 1 signifying
Comparator0 as the reset source; otherwise, this bit reads 0. The Comparator0 reset source remains
functional even when the device is in the low power suspend and sleep states as long as Comparator0 is
also enabled as a wake-up source. The state of the RST pin is unaffected by this reset.
18.6. PCA Watchdog Timer Reset
The programmable watchdog timer (WDT) function of the programmable counter array (PCA) can be used
to prevent software from running out of control during a system malfunction. The PCA WDT function can
be enabled or disabled by software as described in Section “26.4. Watchdog Timer Mode” on page 309;
the WDT is enabled and clocked by SYSCLK / 12 following any reset. If a system malfunction prevents
user software from updating the WDT, a reset is generated and the WDTRSF bit (RSTSRC.5) is set to 1.
The PCA Watchdog Timer reset source is automatically disabled when the device is in the low power
suspend or sleep mode. Upon exit from either low power state, the enabled/disabled state of this reset
source is restored to its previous value.The state of the RST pin is unaffected by this reset.
18.7. Flash Error Reset
If a Flash read/write/erase or program read targets an illegal address, a system reset is generated. This
may occur due to any of the following:
 A Flash write or erase is attempted above user code space. This occurs when PSWE is set to 1 and a
MOVX write operation targets an address above the Lock Byte address.
 A Flash read is attempted above user code space. This occurs when a MOVC operation targets an
address above the Lock Byte address.
 A Program read is attempted above user code space. This occurs when user code attempts to branch
to an address above the Lock Byte address.
 A Flash read, write or erase attempt is restricted due to a Flash security setting (see Section
“14.3. Security Options” on page 151).
 A Flash write or erase is attempted while the V_DD Monitor is disabled.
The FERROR bit (RSTSRC.6) is set following a Flash error reset. The state of the RST pin is unaffected by
this reset.
18.8. SmaRTClock (Real Time Clock) Reset
The SmaRTClock can generate a system reset on two events: SmaRTClock Oscillator Fail or
SmaRTClock Alarm. The SmaRTClock Oscillator Fail event occurs when the SmaRTClock Missing Clock
Detector is enabled and the SmaRTClock clock is below approximately 20 kHz. A SmaRTClock alarm
event occurs when the SmaRTClock Alarm is enabled and the SmaRTClock timer value matches the
ALARMn registers. The SmaRTClock can be configured as a reset source by writing a 1 to the RTC0RE
flag (RSTSRC.7). The SmaRTClock reset remains functional even when the device is in the low power
Suspend or Sleep mode. The state of the RST pin is unaffected by this reset.
Rev. 1.0
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