2010 Microchip Technology Inc.
DS41303G-page 119
PIC18F2XK20/4XK20
9.9
INTn Pin Interrupts
External interrupts on the RB0/INT0, RB1/INT1 and
RB2/INT2 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 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 by software in the Interrupt
Service Routine before re-enabling the interrupt.
All external interrupts (INT0, INT1 and INT2) can wake-
up the processor from Idle or Sleep modes if bit INTxE
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 and INT2 is determined by the
value contained in the interrupt priority bits, INT1IP and
INT2IP of the INTCON3 register. There is no priority bit
associated with INT0. It is always a high priority inter-
rupt source.
9.10
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 regis-
ter pair (FFFFh
0000h) will set TMR0IF. The interrupt
can be enabled/disabled by setting/clearing enable bit,
TMR0IE of the INTCON register. Interrupt priority for
Timer0 is determined by the value contained in the
interrupt priority bit, TMR0IP of the INTCON2 register.
on the Timer0 module.
9.11
PORTB Interrupt-on-Change
An input change on PORTB<7:4> sets flag bit, RBIF of
the INTCON register. The interrupt can be enabled/
disabled by setting/clearing enable bit, RBIE of the
INTCON register. Pins must also be individually
enabled with the IOCB register. Interrupt priority for
PORTB interrupt-on-change is determined by the value
contained in the interrupt priority bit, RBIP of the
INTCON2 register.
9.12
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
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.
and BSR registers during an Interrupt Service Routine.
EXAMPLE 9-1:
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