PIC18F6390 Datasheet, PDF (110/412 Pages) Microchip Technology – 64/80-Pin Flash Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F6390/6490/8390/8490
8.6 INTn 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 INTxF is set. This interrupt can
be disabled by clearing the corresponding enable bit,
INTxE. The interrupt flag bit 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 INTxE 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, 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.
8.7 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 regis-
ter 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
priority bit, TMR0IP (INTCON2<2>). See Section 10.0
“Timer0 Module” for further details on the Timer0
module.
8.8 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>).
8.9 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 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.
EXAMPLE 8-1: 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_TMEP located anywhere
; Restore BSR
; Restore WREG
; Restore STATUS
DS39629B-page 108
Preliminary
 2004 Microchip Technology Inc.