2004 Microchip Technology Inc.
DS30491C-page 355
PIC18F6585/8585/6680/8680
24.2
Watchdog Timer (WDT)
The Watchdog Timer is a free-running, on-chip RC
oscillator which does not require any external compo-
nents. This RC oscillator is separate from the RC
oscillator of the OSC1/CLKI pin. That means that the
WDT will run even if the clock on the OSC1/CLKI and
OSC2/CLKO/RA6 pins of the device has been stopped,
for example, by execution of a SLEEP instruction.
During normal operation, a WDT time-out generates a
device Reset (Watchdog Timer Reset). If the device is
in Sleep mode, a WDT time-out causes the device to
wake-up and continue with normal operation (Watch-
dog Timer wake-up). The TO bit in the RCON register
will be cleared upon a WDT time-out.
The Watchdog Timer is enabled/disabled by a device
configuration bit. If the WDT is enabled, software
execution may not disable this function. When the
WDTEN configuration bit is cleared, the SWDTEN bit
enables/disables the operation of the WDT.
The WDT time-out period values may be found in
under
parameter #31. Values for the WDT postscaler may be
assigned using the configuration bits.
24.2.1
CONTROL REGISTER
readable and writable register which contains a control
bit that allows software to override the WDT enable
configuration bit, only when the configuration bit has
disabled the WDT.
REGISTER 24-15: WDTCON REGISTER
Note 1: The CLRWDT and SLEEP instructions
clear the WDT and the postscaler if
assigned to the WDT and prevent it from
timing out and generating a device Reset
condition.
2: When a CLRWDT instruction is executed
and the postscaler is assigned to the
WDT, the postscaler count will be cleared
but the postscaler assignment is not
changed.
U-0
R/W-0
—
—SWDTEN
bit 7
bit 0
bit 7-1
Unimplemented: Read as ‘0’
bit 0
SWDTEN: Software Controlled Watchdog Timer Enable bit
1
= Watchdog Timer is on
0
= Watchdog Timer is turned off if the WDTEN configuration bit in the Configuration register = 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
- n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown