PIC32MX440F256H-80I Datasheet, PDF (537/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

23.10 Wake-Up from SLEEP or IDLE on
Watchdog Time-Out (NMI)
When the WDT times out in SLEEP or IDLE mode, an
NMI is generated. The NMI causes the CPU code exe-
cution to jump to the device Reset vector. Although the
CPU executes the Reset vector, it is not a device
Reset, peripherals and most CPU registers do not
change their states.
Note:
Any applicable oscillator start-up delays
are applied before the CPU resumes code
execution.
To detect a wake from a Power-Saving mode caused
by WDT expiration, the WDTO (RCON<4>), SLEEP
(RCON<3>), and IDLE (RCON<2>) bits must be
tested. If the WDTO bit is ‘1’ the event was due to a
WDT time-out. The SLEEP and IDLE bits can then be
tested to determine if the WDT event occurred in Sleep
or Idle.
To use a WDT time-out during SLEEP mode as a wake-
up interrupt, a return from interrupt (ERET) instruction
must be used in the start-up code after the event was
determined to be a WDT wake-up. This will cause code
execution to continue from the instruction following the
WAIT instruction that put the device in Power-Saving
mode.
Note:
If a peripheral interrupt and WDT event
occur simultaneously, or in close proxim-
ity, the NMI may not occur, due to the
device being awakened by the peripheral
interrupt. To avoid unexpected WDT
Reset in this scenario, the WDT is auto-
matically cleared when the device
awakens.
See Section 26.0 “Watchdog Timer” for detailed
information on the WDT operation.
PIC32MX3XX/4XX
23.11 Interrupts Coincident with
Power-Saving Instruction
Any peripheral interrupt that coincides with the execu-
tion of a WAIT instruction will be held off until entry into
SLEEP or IDLE mode has completed. The device will
then wake-up from SLEEP or IDLE mode.
23.12 I/O Pins Associated with
Power-Saving Modes
No device pins are associated with Power-Saving
modes.
© 2008 Microchip Technology Inc.
Preliminary
DS61143E-page 535