PIC18F25J50 MICROCHIP [Microchip Technology], PIC18F25J50 Datasheet - Page 60

• Manufacturer Part Number: PIC18F25J50
• Description: 28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F46J50 FAMILY
4.7
The Ultra Low-Power Wake-up (ULPWU) on RA0 allows
a slow falling voltage to generate an interrupt-on-change
without excess current consumption.
Follow these steps to use this feature:
1.
2.
3.
4.
5.
6.
7.
8.
When the voltage on RA0 drops below V
will be generated, which will cause the device to
wake-up and execute the next instruction.
This feature provides a low-power technique for
periodically waking up the device from Sleep mode.
The time-out is dependent on the discharge time of the
RC circuit on RA0.
When the ULPWU module causes the device to
wake-up from Sleep mode, the WDTCON<ULPLVL>
bit is set. When the ULPWU module causes the device
to
(DSWAKEL<5>) bit is set. Software can check these
bits upon wake-up to determine the wake-up source.
Also in Sleep mode, only the remappable output func-
tion, ULPWU, will output this bit value to an RPn pin for
externally detecting wake-up events.
DS39931D-page 60
Configure a remappable output pin to output the
ULPOUT signal.
Map an INTx interrupt-on-change input function to
the same pin as used for the ULPOUT output func-
tion. Alternatively, in Step 1, configure ULPOUT to
output onto a PORTB interrupt-on-change pin.
Charge the capacitor on RA0 by configuring the
RA0 pin to an output and setting it to ‘1’.
Enable interrupt-on-change (PIE bit) for the
corresponding pin selected in Step 2.
Stop charging the capacitor by configuring RA0
as an input.
Discharge the capacitor by setting the ULPEN
and ULPSINK bits in the WDTCON register.
Configure Sleep mode.
Enter Sleep mode.
wake-up
Ultra Low-Power Wake-up
from
Deep
Sleep,
IL
the
, an interrupt
DSULP
See
A series resistor between RA0 and the external
capacitor provides overcurrent protection for the
RA0/AN0/C1INA/ULPWU/RP0 pin and can allow for
software calibration of the time-out (see
FIGURE 4-9:
A timer can be used to measure the charge time and
discharge time of the capacitor. The charge time can
then be adjusted to provide the desired interrupt delay.
This technique will compensate for the affects of
temperature, voltage and component accuracy. The
ULPWU peripheral can also be configured as a simple
Programmable
temperature sensor.
Note:
Note:
Example 4-1
For module-related bit definitions, see the
WDTCON
“Watchdog Timer (WDT)”
DSWAKEL register
For more information, refer to AN879,
“Using the Microchip Ultra Low-Power
Wake-up
(DS00879).
RA0
Low-Voltage
for initializing the ULPWU module.
SERIAL RESISTOR
Module”
 2011 Microchip Technology Inc.
register
R
1
(Register
Detect
application
in
C
1
Section 27.2
Figure
4-6).
(LVD)
and the
4-9).
note
or