PIC12C508A-04/EJW MICROCHIP [Microchip Technology], PIC12C508A-04/EJW Datasheet - Page 43

• Manufacturer Part Number: PIC12C508A-04/EJW
• Description: 8-Pin, 8-Bit CMOS Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

8.6.1
The WDT has a nominal time-out period of 18 ms,
(with no prescaler). If a longer time-out period is
desired, a prescaler with a division ratio of up to 1:128
can be assigned to the WDT (under software control)
by writing to the OPTION register. Thus, a time-out
period of a nominal 2.3 seconds can be realized.
These periods vary with temperature, V
part process variations (see DC specs).
Under worst case conditions (V
= Max., max. WDT prescaler), it may take several
seconds before a WDT time-out occurs.
FIGURE 8-12: WATCHDOG TIMER BLOCK DIAGRAM
TABLE 8-6:
N/A
Legend: Shaded boxes = Not used by Watchdog Timer, — = unimplemented, read as ’0’, u = unchanged
Address
1999 Microchip Technology Inc.
WDT PERIOD
OPTION
Name
Note: T0CS, T0SE, PSA, PS2:PS0
SUMMARY OF REGISTERS ASSOCIATED WITH THE WATCHDOG TIMER
Configuration Bit
WDT Enable
Watchdog
are bits in the OPTION register.
Timer
GPWU
Bit 7
From Timer0 Clock Source
(Figure 8-5)
DD
= Min., Temperature
GPPU
Bit 6
DD
and part-to-
T0CS
1
0
Bit 5
PSA
M
U
X
T0SE
Bit 4
Bit 3
PSA
0
8.6.2
The CLRWDT instruction clears the WDT and the
postscaler, if assigned to the WDT, and prevents it
from timing out and generating a device RESET.
The SLEEP instruction resets the WDT and the
postscaler, if assigned to the WDT. This gives the
maximum SLEEP time before a WDT wake-up reset.
Time-out
8 - to - 1 MUX
WDT
MUX
Postscaler
Postscaler
Bit 2
PS2
1
WDT PROGRAMMING CONSIDERATIONS
Bit 1
PS1
PSA
To Timer0 (Figure 8-4)
Bit 0
PS0
PS2:PS0
PIC12C5XX
1111 1111
Power-On
Value on
Reset
DS40139E-page 43
1111 1111
All Other
Value on
Resets