PIC18F2450 MICROCHIP [Microchip Technology], PIC18F2450 Datasheet - Page 99

• Manufacturer Part Number: PIC18F2450
• Description: 28/40/44-Pin, High-Performance, 12 MIPS, Enhanced Flash, USB Microcontrollers with nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

8.7
External interrupts on the RB0/AN12/INT0, RB1/AN10/
INT1and RB2/AN8/INT2/VMO 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 and INT2) can wake-
up the processor from the power-managed modes if bit,
INTxIE, was set prior to going into the 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.
EXAMPLE 8-1:
© 2006 Microchip Technology Inc.
MOVWF
MOVFF
MOVFF
;
; USER ISR CODE
;
MOVFF
MOVF
MOVFF
INTn Pin Interrupts
W_TEMP
STATUS, STATUS_TEMP
BSR, BSR_TEMP
BSR_TEMP, BSR
W_TEMP, W
STATUS_TEMP, STATUS
SAVING STATUS, WREG AND BSR REGISTERS IN RAM
Advance Information
; W_TEMP is in virtual bank
; STATUS_TEMP located anywhere
; BSR_TMEP located anywhere
; Restore BSR
; Restore WREG
; Restore STATUS
8.8
In 8-bit mode (which is the default), an overflow in the
TMR0 register (FFh
16-bit mode, an overflow in the TMR0H:TMR0L
register pair (FFFFh
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 “Timer2 Module” for further details on
the Timer0 module.
8.9
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>).
8.10
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 5.3
“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 8-1 saves and restores the WREG,
STATUS and BSR registers during an Interrupt Service
Routine.
TMR0 Interrupt
PORTB Interrupt-on-Change
Context Saving During Interrupts
PIC18F2450/4450
00h) will set flag bit, TMR0IF. In
0000h) will set TMR0IF. The
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