System Reset and Initialization
2-2 System Resets, Interrupts, and Operating Modes
2.1 System Reset and Initialization
The system reset circuitry shown in Figure 2−1 sources both a power-on reset
(POR) and a power-up clear (PUC) signal. Different events trigger these reset
signals and different initial conditions exist depending on which signal was
generated.

Figure 2−1.Power-On Reset and Power-Up Clear Schematic

POR
Latch
S
R
PUC
Latch
S
R
Resetwd1
Resetwd2
S
S
Delay
RST/NMI
WDTNMI
WDTSSEL
WDTQn
WDTIFG
EQU
MCLK
POR
PUC
S
(from flash module)
KEYV
SVS_POR
0 V
VCC
0 V
Brownout
Reset
† From watchdog timer peripheral module
~ 50us
A POR is a device reset. A POR is only generated by the following three
events:
-Powering up the device
-A low signal on the RST/NMI pin when configured in the reset mode
-An SVS low condition when PORON = 1.
A PUC is always generated when a POR is generated, but a POR is not
generated by a PUC. The following events trigger a PUC:
-A POR signal
-Watchdog timer expiration when in watchdog mode only
-Watchdog timer security key violation
-A Flash memory security key violation