PIC16F819 Microchip Technology Inc., PIC16F819 Datasheet - Page 99

• Manufacturer Part Number: PIC16F819
• Description: 18/20-pin Enhanced Flash Microcontrollers With Nanowatt Technology
• Manufacturer: Microchip Technology Inc.

12.10.1
External interrupt on the RB0/INT pin is edge triggered,
either rising if bit INTEDG (OPTION_REG<6>) is set,
or falling if the INTEDG bit is clear. When a valid edge
appears on the RB0/INT pin, flag bit, INTF
(INTCON<1>), is set. This interrupt can be disabled by
clearing enable bit, INTE (INTCON<4>). Flag bit INTF
must be cleared in software in the Interrupt Service
Routine before re-enabling this interrupt. The INT inter-
rupt can wake-up the processor from Sleep if bit INTE
was set prior to going into Sleep. The status of Global
Interrupt Enable bit, GIE, decides whether or not the
processor branches to the interrupt vector following
wake-up. See Section 12.13 “Power-Down Mode
(Sleep)” for details on Sleep mode.
12.10.2
An overflow (FFh
flag bit, TMR0IF (INTCON<2>). The interrupt can be
enabled/disabled
TMR0IE (INTCON<5>) (see Section 6.0 “Timer0
Module”).
EXAMPLE 12-1:
 2004 Microchip Technology Inc.
MOVWF
SWAPF
CLRF
MOVWF
:
:(ISR)
:
SWAPF
MOVWF
SWAPF
SWAPF
INT INTERRUPT
TMR0 INTERRUPT
W_TEMP
STATUS, W
STATUS
STATUS_TEMP
STATUS_TEMP, W
STATUS
W_TEMP, F
W_TEMP, W
by
00h) in the TMR0 register will set
SAVING STATUS AND W REGISTERS IN RAM
setting/clearing
;Copy W to TEMP register
;Swap status to be saved into W
;bank 0, regardless of current bank, Clears IRP,RP1,RP0
;Save status to bank zero STATUS_TEMP register
;Insert user code here
;Swap STATUS_TEMP register into W
;(sets bank to original state)
;Move W into STATUS register
;Swap W_TEMP
;Swap W_TEMP into W
enable
bit,
12.10.3
An input change on PORTB<7:4> sets flag bit, RBIF
(INTCON<0>). The interrupt can be enabled/disabled
by setting/clearing enable bit, RBIE (INTCON<3>). See
Section 3.2 “EECON1 and EECON2 Registers”.
12.11 Context Saving During Interrupts
During an interrupt, only the return PC value is saved
on the stack. Typically, users may wish to save key
registers during an interrupt (i.e., W, Status registers).
This will have to be implemented in software as shown
in Example 12-1.
For PIC16F818 devices, the upper 64 bytes of each
bank are common. Temporary holding registers,
W_TEMP and STATUS_TEMP, should be placed here.
These 64 locations do not require banking and
therefore, make it easier for context save and restore.
For PIC16F819 devices, the upper 16 bytes of each
bank are common.
PORTB INTCON CHANGE
PIC16F818/819
DS39598E-page 97