Datasheet

PIC18F1230/1330
 2009 Microchip Technology Inc. DS39758D-page 105
11.6 INTx Pin Interrupts
External interrupts on the RA0/INT0, RA1/INT1, RB2/
INT2 and RB3/INT3 pins are edge-triggered. If the
corresponding INTEDGx bit in the INTCON2 register is
set (= 1), the interrupt is triggered by a rising edge; if
the bit is clear, the trigger is on the falling edge. When
a valid edge appears on the pin, the corresponding flag
bit, INTxIF, is set. This interrupt can be disabled by
clearing the corresponding enable bit, INTxIE. Flag bit,
INTxIF, must be cleared in software in the Interrupt
Service Routine before re-enabling the interrupt.
All external interrupts (INT0, INT1, INT2 and INT3) can
wake-up the processor from Idle or Sleep modes if bit
INTxIE was set prior to going into those modes. If the
Global Interrupt Enable bit, GIE, is set, the processor
will branch to the interrupt vector following wake-up.
Interrupt priority for INT1, INT2 and INT3 is determined
by the value contained in the interrupt priority bits,
INT1IP (INTCON3<6>), INT2IP (INTCON3<7>) and
INT3IP (INTCON2<1>). There is no priority bit
associated with INT0. It is always a high-priority
interrupt source.
11.7 TMR0 Interrupt
In 8-bit mode (which is the default), an overflow in the
TMR0 register (FFh  00h) will set flag bit, TMR0IF. In
16-bit mode, an overflow in the TMR0H:TMR0L
register pair (FFFFh 0000h) will set TMR0IF. The
interrupt can be enabled/disabled by setting/clearing
enable bit, TMR0IE (INTCON<5>). Interrupt priority for
Timer0 is determined by the value contained in the
interrupt priority bit, TMR0IP (INTCON2<2>). See
Section 12.0 “Timer0 Module” for further details on
the Timer0 module.
11.8 Interrupt-on-Change
An input change on PORTA<1:0> and/or PORTB<2:3>
sets flag bit, RBIF (INTCON<0>). The interrupt can be
enabled/disabled by setting/clearing enable bit, RBIE
(INTCON<3>). Interrupt priority for interrupt-on-change
is determined by the value contained in the interrupt
priority bit, RBIP (INTCON2<0>).
11.9 Context Saving During Interrupts
During interrupts, the return PC address is saved on
the stack. Additionally, the WREG, STATUS and BSR
registers are saved on the fast return stack. If a fast
return from interrupt is not used (see Section 6.3
“Data Memory Organization”), the user may need to
save the WREG, STATUS and BSR registers on entry
to the Interrupt Service Routine. Depending on the
user’s application, other registers may also need to be
saved. Example 11-1 saves and restores the WREG,
STATUS and BSR registers during an Interrupt Service
Routine.
EXAMPLE 11-1: SAVING STATUS, WREG AND BSR REGISTERS IN RAM
MOVWF W_TEMP ; W_TEMP is in virtual bank
MOVFF STATUS, STATUS_TEMP ; STATUS_TEMP located anywhere
MOVFF BSR, BSR_TEMP ; BSR_TMEP located anywhere
;
; USER ISR CODE
;
MOVFF BSR_TEMP, BSR ; Restore BSR
MOVF W_TEMP, W ; Restore WREG
MOVFF STATUS_TEMP, STATUS ; Restore STATUS