PIC16F684-I/SLG Microchip, PIC16F684-I/SLG Datasheet - Page 36

• Manufacturer Part Number: PIC16F684-I/SLG
• Description: pic, flash, Microcontrollers, Microprocessors, Semiconductors and Actives, ic, mcu
• Manufacturer: Microchip

PIC16F684
4.2.3
The Ultra Low-power Wake-up (ULPWU) on RA0
allows a slow falling voltage to generate an interrupt-
on-change on RA0 without excess current consump-
tion. The mode is selected by setting the ULPWUE bit
(PCON<5>). This enables a small current sink which
can be used to discharge a capacitor on RA0.
To use this feature, the RA0 pin is configured to output
‘1’ to charge the capacitor, interrupt-on-change for RA0
is enabled, and RA0 is configured as an input. The
ULPWUE bit is set to begin the discharge and a SLEEP
instruction is performed. When the voltage on RA0 drops
below V
the device to wake-up. Depending on the state of the
GIE bit (INTCON<7>), the device will either jump to the
interrupt vector (0004h) or execute the next instruction
when the interrupt event occurs. See Section 4.2.2
“Interrupt-on-change” and Section 12.4.3 “PORTA
Interrupt” for more information.
This feature provides a low-power technique for
periodically waking up the device from Sleep. The
time-out is dependent on the discharge time of the RC
circuit on RA0. See Example 4-2 for initializing the
Ultra Low-Power Wake-up module.
DS41202C-page 34
IL
, an interrupt will be generated which will cause
ULTRA LOW-POWER WAKE-UP
Preliminary
The series resistor provides overcurrent protection for
the RA0 pin and can allow for software calibration of
the time-out (see Figure 4-1). A timer can be used to
measure the charge time and discharge time of the
capacitor. The charge time can then be adjusted to pro-
vide the desired interrupt delay. This technique will
compensate for the affects of temperature, voltage and
component accuracy. The Ultra Low-power Wake-up
peripheral can also be configured as a simple
Programmable Low Voltage Detect or temperature
sensor.
EXAMPLE 4-2:
BCF
BSF
MOVLW
MOVWF
BSF
BCF
BCF
CALL
BSF
BSF
BSF
MOVLW
MOVWF
SLEEP
Note:
STATUS,RP0
PORTA,0
H’7’
CMCON0
STATUS,RP0
ANSEL,0
TRISA,0
CapDelay
PCON,ULPWUE ;Enable ULP Wake-up
IOCA,0
TRISA,0
B’10001000’ ;Enable interrupt
INTCON
For more information, refer to AN879,
“Using the Microchip Ultra Low-Power
Wake-up
(DS00879).
ULTRA LOW-POWER
WAKE-UP INITIALIZATION
Module”
 2004 Microchip Technology Inc.
;Bank 0
;Set RA0 data latch
;Turn off
;comparators
;Bank 1
;RA0 to digital I/O
;Output high to
; charge capacitor
;Select RA0 IOC
;RA0 to input
; and clear flag
;Wait for IOC
Application
Note