PIC16F7X7 datasheet(187/276 Pages) MICROCHIP

187 / 276 page

 2004 Microchip Technology Inc.

DS30498C-page 185

PIC16F7X7

15.15.1

INT INTERRUPT

External interrupt on the RB0/INT pin is edge-triggered,

either rising if bit INTEDG (OPTION_REG<6>) is set or

falling if the INTEDG bit is clear. When a valid edge

appears

the

RB0/INT

pin,

flag

bit

INT0IF

(INTCON<1>) is set. This interrupt can be disabled by

clearing enable bit, INT0IE (INTCON<4>). Flag bit

INT0IF must be cleared in software in the Interrupt

Service Routine before re-enabling this interrupt. The

INT interrupt can wake-up the processor from Sleep if

bit INT0IE was set prior to going into Sleep. The status

of Global Interrupt Enable bit, GIE, decides whether or

not the processor branches to the interrupt vector

following wake-up. See Section 15.18 “Power-Down

Mode (Sleep)” for details on Sleep mode.

15.15.2

TMR0 INTERRUPT

An overflow (FFh

→ 00h) in the TMR0 register will set

flag bit, TMR0IF (INTCON<2>). The interrupt can be

enabled/disabled

setting/clearing

enable

bit,

TMR0IE (INTCON<5>), see Section 6.0 “Timer0

Module”.

15.15.3

PORTB INTCON 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<4>), see

Section 2.2 “Data Memory Organization”.

15.16 Context Saving During Interrupts

During an interrupt, only the return PC value is saved

on the stack. Typically, users may wish to save key

registers during an interrupt (i.e., W, Status registers).

Since the upper 16 bytes of each bank are common in

the PIC16F7X7 devices, temporary holding registers,

W_TEMP,

STATUS_TEMP

and

PCLATH_TEMP,

should be placed in here. These 16 locations don’t

require banking and therefore, make it easier for

context save and restore. The same code shown in

Example 15-1 can be used.

EXAMPLE 15-1:

SAVING STATUS AND W REGISTERS IN RAM

MOVWF

W_TEMP

;Copy W to TEMP register

SWAPF

STATUS, W

;Swap status to be saved into W

CLRF

STATUS

;bank 0, regardless of current bank, Clears IRP,RP1,RP0

MOVWF

STATUS_TEMP

;Save status to bank zero STATUS_TEMP register

:(ISR)

;Insert user code here

SWAPF

STATUS_TEMP, W

;Swap STATUS_TEMP register into W

;(sets bank to original state)

MOVWF

STATUS

;Move W into STATUS register

SWAPF

W_TEMP, F

;Swap W_TEMP

SWAPF

W_TEMP, W

;Swap W_TEMP into W

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