PIC16F887-E/P Microchip Technology Inc., PIC16F887-E/P Datasheet - Page 43

• Manufacturer Part Number: PIC16F887-E/P
• Description: 40 PIN, 14KB FLASH, 368 RAM, 36 I/O, PDIP
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F887-E/P

• A/d Inputs: 14-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 256 Bytes
• Frequency: 20 MHz
• Input Output: 35
• Interface: I2C/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 14K Bytes
• Ram Size: 368 Bytes
• Resistance, Drain To Source On: Bytes
• Serial Interface: MSSP or EUSART
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

3.2.2
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.
Follow these steps to use this feature:
a)
b)
c)
d)
e)
When the voltage on RA0 drops below V
will be generated which will cause the device to
wake-up and execute the next instruction. If the GIE bit
of the INTCON register is set, the device will then call
the interrupt vector (0004h).
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 3-2 for initializing the
Ultra Low-Power Wake-up module.
© 2008 Microchip Technology Inc.
Charge the capacitor on RA0 by configuring the
RA0 pin to output (= 1).
Configure RA0 as an input.
Set the ULPWUIE bit of the PIE2 register to
enable interrupt.
Set the ULPWUE bit of the PCON register to
begin the capacitor discharge.
Execute a SLEEP instruction.
ULTRA LOW-POWER WAKE-UP
IL
, an interrupt
PIC16F882/883/884/886/887
A series resistor between RA0 and the external
capacitor provides overcurrent protection for the
RA0/AN0/ULPWU/C12IN0- pin and can allow for
software calibration of the time-out (see Figure 3-1). 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.
EXAMPLE 3-2:
BANKSEL PORTA
BSF
BANKSEL ANSEL
BCF
BANKSEL TRISA
BCF
CALL
BANKSEL PIR2
BCF
BANKSEL PCON
BSF
BSF
BSF
MOVLW
MOVWF
SLEEP
NOP
Note:
PORTA,0
ANSEL,0
TRISA,0
CapDelay
PIR2,ULPWUIF
PCON,ULPWUE
TRISA,0
PIE2, ULPWUIE
B’11000000’
INTCON
For more information, refer to AN879,
“Using the Microchip Ultra Low-Power
Wake-up
(DS00879).
ULTRA LOW-POWER
WAKE-UP INITIALIZATION
Module”
;
;Set RA0 data latch
;
;RA0 to digital I/O
;
;Output high to
;charge capacitor
;
;Clear flag
;Enable ULP Wake-up
;RA0 to input
;Enable interrupt
;Enable peripheral
;interrupt
;Wait for IOC
;
Application
DS41291E-page 41
Note