PIC16F636-I/P Microchip Technology Inc., PIC16F636-I/P Datasheet - Page 45

• Manufacturer Part Number: PIC16F636-I/P
• Description: 14 PIN, 3.5 KB FLASH, 128 RAM, 12 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F636-I/P

• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 12
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 14-pin PDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 128 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

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 consumption. 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 12.9.3 “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.
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.
© 2005 Microchip Technology Inc.
Note:
IL
, an interrupt will be generated which will cause
ULTRA LOW-POWER WAKE-UP
For more information, refer to the
Application Note AN879, “Using the
Microchip Ultra Low-Power Wake-up
Module” (DS00879).
PIC12F635/PIC16F636/639
Preliminary
EXAMPLE 4-2:
BCF
BCF
BSF
MOVLW
MOVWF
BSF
BCF
BCF
CALL
BSF
BSF
BSF
MOVLW
MOVWF
SLEEP
STATUS,RP0
STATUS,RP1
PORTA,0
H’7’
CMCON0
STATUS,RP0
STATUS,RP1
TRISA,0
CapDelay
PCON,ULPWUE ;Enable ULP Wake-up
IOCA,0
TRISA,0
B’10001000’ ;Enable interrupt
INTCON
ULTRA LOW-POWER
WAKE-UP INITIALIZATION
;Bank 0
;
;Set RA0 data latch
;Turn off
; comparators
;Bank 1
;
;Output high to
; charge capacitor
;Select RA0 IOC
;RA0 to input
; and clear flag
;Wait for IOC
DS41232B-page 43