PIC16C63A Microchip Technology, PIC16C63A Datasheet - Page 92

• Manufacturer Part Number: PIC16C63A
• Description: 28/40-Pin 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

PIC16C63A/65B/73B/74B
11.12
The Watchdog Timer is a free running on-chip RC oscil-
lator, which does not require any external components.
This RC oscillator is separate from the RC oscillator of
the OSC1/CLKIN pin. That means that the WDT will
run, even if the clock on the OSC1/CLKIN and OSC2/
CLKOUT 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 STATUS register
will be cleared upon a Watchdog Timer time-out.
The WDT can be permanently disabled by clearing
configuration bit WDTE (Section 11.1).
FIGURE 11-12: WATCHDOG TIMER BLOCK DIAGRAM
FIGURE 11-13: SUMMARY OF WATCHDOG TIMER REGISTERS
DS30605A-page 92
Address
2007h
81h
Legend: Shaded cells are not used by the Watchdog Timer.
Note 1: See Figure 11-1 for operation of these bits.
Note: PSA and PS2:PS0 are bits in the OPTION_REG register.
Watchdog Timer (WDT)
Name
Config. bits
OPTION_REG
WDT Timer
Enable Bit
WDT
RBPU
Bit 7
From TMR0 Clock Source
(Figure 4-2)
(1)
BODEN
INTEDG
Bit 6
0
1
(1)
PSA
M
U
X
T0CS
Bit 5
CP1
T0SE
WDT time-out period values may be found in the Elec-
trical Specifications section under parameter #31. Val-
ues for the WDT prescaler (actually a postscaler, but
shared with the Timer0 prescaler) may be assigned
using the OPTION_REG register.
.
Bit 4
CP0
0
Note:
Note:
Time-out
8 - to - 1 MUX
MUX
WDT
Postscaler
PWRTE
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.
When a CLRWDT instruction is executed
and the prescaler is assigned to the WDT,
the prescaler count will be cleared, but the
prescaler assignment is not changed.
1
Bit 3
PSA
8
(1)
PSA
To TMR0 (Figure 4-2)
WDTE
Bit 2
PS2
1998 Microchip Technology Inc.
PS2:PS0
FOSC1
Bit 1
PS1
FOSC0
Bit 0
PS0