PIC16CR58A Microchip Technology, PIC16CR58A Datasheet - Page 39

• Manufacturer Part Number: PIC16CR58A
• Description: ROM-Based 8-Bit CMOS Microcontroller Series
• Manufacturer: Microchip Technology

7.5
The Device Reset Timer (DRT) provides a fixed 18 ms
nominal time-out on reset. The DRT operates on an
internal RC oscillator. The processor is kept in RESET
as long as the DRT is active. The DRT delay allows
V
stabilize.
Oscillator circuits based on crystals or ceramic
resonators require a certain time after power-up to
establish a stable oscillation. The on-chip DRT keeps
the device in a RESET condition for approximately 18
ms after the voltage on the MCLR/V
reached a logic high (V
networks connected to the MCLR input are not
required in most cases, allowing for savings in
cost-sensitive and/or space restricted applications.
The Device Reset time delay will vary from device to
device due to V
variation. See AC parameters for details.
The DRT will also be triggered upon a Watchdog Timer
time-out. This is particularly important for applications
using the WDT to wake the PIC16C5X from SLEEP
mode automatically.
DD
1998 Microchip Technology Inc.
to rise above V
Device Reset Timer (DRT)
DD
DD
, temperature, and process
min., and for the oscillator to
IH
) level. Thus, external RC
PP
pin has
Preliminary
7.6
The Watchdog Timer (WDT) is a free running on-chip
RC oscillator 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 have been stopped, for
example, by execution of a SLEEP instruction. During
normal operation or SLEEP, a WDT reset or wake-up
reset generates a device RESET.
The TO bit (STATUS<4>) will be cleared upon a
Watchdog Timer reset.
The
programming the configuration bit WDTE as a '0'
(Section 7.1). Refer to the PIC16C5X Programming
Specifications
determine how to access the configuration word.
7.6.1
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, time-out a
period of a nominal 2.3 seconds can be realized.
These periods vary with temperature, V
part-to-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.
7.6.2
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.
WDT
Watchdog Timer (WDT) (not
implemented on PIC16C52)
WDT PERIOD
WDT PROGRAMMING CONSIDERATIONS
can
(Literature
be
permanently
PIC16C5X
Number
DD
= Min., Temperature
DS30453B-page 39
DS30190)
disabled
DD
and
by
to