PIC18F97J60 Datasheet, PDF (58/474 Pages) Microchip Technology – 64/80/100-Pin, High-Performance, 1 Mbit Flash Microcontrollers with Ethernet

PIC18F97J60 FAMILY
4.5 Power-up Timer (PWRT)
PIC18F97J60 family of devices incorporates an
on-chip Power-up Timer (PWRT) to help regulate the
Power-on Reset process. The PWRT is always
enabled. The main function is to ensure that the device
voltage is stable before code is executed.
The Power-up Timer (PWRT) of the PIC18F97J60 fam-
ily devices is an 11-bit counter which uses the INTRC
source as the clock input. This yields an approximate
time interval of 2048 x 32 μs = 66 ms. While the PWRT
is counting, the device is held in Reset.
The power-up time delay depends on the INTRC clock
and will vary from chip-to-chip due to temperature and
process variation. See DC parameter 33 for details.
4.5.1 TIME-OUT SEQUENCE
The PWRT time-out is invoked after the POR pulse has
cleared. The total time-out will vary based on the status
of the PWRT. Figure 4-3, Figure 4-4, Figure 4-5 and
Figure 4-6 all depict time-out sequences on power-up.
Since the time-outs occur from the POR pulse, if MCLR
is kept low long enough, the PWRT will expire. Bringing
MCLR high will begin execution immediately
(Figure 4-5). This is useful for testing purposes or to
synchronize more than one PIC18FXXJ6X device
operating in parallel.
FIGURE 4-3:
TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD, VDD RISE < TPWRT)
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
INTERNAL RESET
TPWRT
FIGURE 4-4:
TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1
VDD
MCLR
INTERNAL POR
PWRT TIME-OUT
INTERNAL RESET
TPWRT
DS39762A-page 56
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© 2006 Microchip Technology Inc.