Microchip Technology DV164136 Data Sheet
PIC18F87J11 FAMILY
DS39778E-page 134
2007-2012 Microchip Technology Inc.
10.6
INTx Pin Interrupts
External interrupts on the RB0/INT0, RB1/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 RBx/INTx 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 the power-managed
modes if bit, INTxIE, was set prior to going into the
power-managed modes, with the exception of Deep
Sleep, which can only be woken from INT0. 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.
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 RBx/INTx 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 the power-managed
modes if bit, INTxIE, was set prior to going into the
power-managed modes, with the exception of Deep
Sleep, which can only be woken from INT0. 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.
10.7
TMR0 Interrupt
In 8-bit mode (which is the default), an overflow in the
TMR0 register (FFh
TMR0 register (FFh
00h) will set flag bit, TMR0IF. In
16-bit mode, an overflow in the TMR0H:TMR0L register
pair (FFFFh
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 prior-
ity bit, TMR0IP (INTCON2<2>). See
TMR0IE (INTCON<5>). Interrupt priority for Timer0 is
determined by the value contained in the interrupt prior-
ity bit, TMR0IP (INTCON2<2>). See
for further details on the Timer0
module.
10.8
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>).
(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>).
10.9
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
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
), 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.
to the Interrupt Service Routine. Depending on the
user’s application, other registers may also need to be
saved.
saves and restores the WREG,
STATUS and BSR registers during an Interrupt Service
Routine.
Routine.
EXAMPLE 10-1:
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