PIC18F6X2X Datasheet, PDF (106/386 Pages) Microchip Technology – 64/80-Pin High Performance, 64-Kbyte Enhanced FLASH Microcontrollers with A/D

PIC18F6X2X/8X2X
9.6 INT0 Interrupt
External interrupts on the RB0/INT0, RB1/INT1,
RB2/INT2 and RB3/INT3 pins are edge-triggered:
either rising, if the corresponding INTEDGx bit is set in
the INTCON2 register or falling, if the INTEDGx bit is
clear. When a valid edge appears on the RBx/INTx pin,
the corresponding flag bit, INTxF, is set. This interrupt
can be disabled by clearing the corresponding enable
bit, INTxE. Flag bit, INTxF, 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 SLEEP if bit
INTxIE was set prior to going into SLEEP. If the global
interrupt enable bit GIE is set, the processor will branch
to the interrupt vector following wake-up.
The 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.
9.7 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
registers (FFFFh → 0000h) will set flag bit 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 11.0 for further details on the Timer0 module.
9.8 PORTB Interrupt-on-Change
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>).
Interrupt priority for PORTB interrupt-on-change is
determined by the value contained in the interrupt
priority bit, RBIP (INTCON2<0>).
9.9 Context Saving During Interrupts
During an interrupt, the return PC value 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 4.3), the
user may need to save the WREG, STATUS and BSR
registers in software. Depending on the user’s
application, other registers may also need to be saved.
Example 9-1 saves and restores the WREG, STATUS
and BSR registers during an Interrupt Service Routine.
EXAMPLE 9-1: SAVING STATUS, WREG AND BSR REGISTERS IN RAM
MOVWF W_TEMP
MOVFF STATUS, STATUS_TEMP
MOVFF BSR, BSR_TEMP
;
; USER ISR CODE
;
MOVFF BSR_TEMP, BSR
MOVF W_TEMP, W
MOVFF STATUS_TEMP,STATUS
; W_TEMP is in virtual bank
; STATUS_TEMP located anywhere
; BSR located anywhere
; Restore BSR
; Restore WREG
; Restore STATUS
DS39612A-page 104
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