PIC18LF4420T-I/SO 查看數據表（PDF） - Microchip Technology

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PIC18LF4420T-I/SO

28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

Microchip Technology 

PIC18F2420/2520/4420/4520

9.6 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 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 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

(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 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 pri-

ority bit, TMR0IP (INTCON2<2>). See Section 11.0

“Timer0 Module” for further details on 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 reg-

isters 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 9-1 saves and restores the WREG, Status

and BSR registers during an Interrupt Service Routine.

EXAMPLE 9-1: 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

 2004 Microchip Technology Inc.

Preliminary

DS39631A-page 103

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