![](http://datasheet.mmic.net.cn/Microchip-Technology/ENC624J600T-I-PT_datasheet_97264/ENC624J600T-I-PT_101.png)
2007 Microchip Technology Inc.
DS39599G-page 99
PIC18F2220/2320/4220/4320
9.6
INTx Pin Interrupts
External interrupts on the RB0/INT0, RB1/INT1 and
RB2/INT2 pins are edge triggered: either rising if the
corresponding INTEDGx bit is set in the INTCON2 reg-
ister, or falling if the INTEDGx bit is clear. 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 and INT2) can wake-up
the processor from the power-managed modes if bit
INTxIE was set prior to going into power-managed
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 (INTCON3<6>) and INT2IP (INTCON3<7>).
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
(FFh
→ 00h) in the TMR0 register will set flag bit
TMR0IF. In 16-bit mode, an overflow (FFFFh
→ 0000h)
in the TMR0H:TMR0L registers will set flag bit TMR0IF.
The interrupt can be enabled/disabled by setting/clear-
ing enable bit, TMR0IE (INTCON<5>). Interrupt priority
for Timer0 is determined by the value contained in the
interrupt priority bit, TMR0IP (INTCON2<2>). See
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 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