PIC16F684T-E/ST Microchip Technology, PIC16F684T-E/ST Datasheet - Page 36

• Manufacturer Part Number: PIC16F684T-E/ST
• Description: IC PIC MCU FLASH 2KX14 14TSSOP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F684T-E/ST

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 12
• Program Memory Size: 3.5KB (2K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 14-TSSOP
• For Use With: XLT14SS-1 - SOCKET TRANSITION 14DIP/14SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Connectivity: -

PIC16F684
4.2.4
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
consumption. The mode is selected by setting the
ULPWUE bit of the PCON register. This enables a small
current sink which can be used to discharge a capacitor
on RA0.
To use this feature, the RA0 pin is first configured to output
‘1’ to charge the capacitor. Then 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
instruction. If the GIE bit of the INTCON register is set, the
device will call the interrupt service routine (0004h). See
Section 4.2.3
Section 12.4.3 “PORTA Interrupt-on-Change” 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.
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
provide 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.
DS41202F-page 34
IL
, the device will wake-up and execute the next
ULTRA LOW-POWER WAKE-UP
“Interrupt-on-Change”
and
EXAMPLE 4-2:
BANKSEL CMCON0
MOVLW
MOVWF
BANKSEL ANSEL
BCF
BCF
BANKSEL PORTA
BSF
CALL
BANKSEL PCON
BSF
BSF
BSF
MOVLW
MOVWF
SLEEP
Note:
H’7’
CMCON0
ANSEL,0
TRISA,0
PORTA,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
© 2007 Microchip Technology Inc.
Module”
;
;Turn off
;comparators
;
;RA0 to digital I/O
;Output high to
;
;charge capacitor
;
;
;Select RA0 IOC
;RA0 to input
; and clear flag
;Wait for IOC
Application
Note