PIC16F870SLASHP datasheet(100/156 Pages) MICROCHIP

100 / 156 page

PIC16F870/871

DS30569A-page 100

Preliminary

11.10.1 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

INTF

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

clearing enable bit INTE (INTCON<4>). Flag bit INTF

must be cleared in software in the interrupt service rou-

tine before re-enabling this interrupt. The INT interrupt

can wake-up the processor from SLEEP, if bit INTE was

set prior to going into SLEEP. The status of global inter-

rupt enable bit GIE decides whether or not the proces-

sor branches to the interrupt vector following wake-up.

See Section 11.13 for details on SLEEP mode.

11.10.2 TMR0 INTERRUPT

An overflow (FFh

→ 00h) in the TMR0 register will set

flag bit T0IF (INTCON<2>). The interrupt can be

enabled/disabled by setting/clearing enable bit T0IE

(INTCON<5>). (Section 5.0)

11.10.3 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>).

(Section 3.2)

11.11

Context Saving During Interrupts

During an interrupt, only the return PC value is saved

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

isters during an interrupt, (i.e., W register and STATUS

Since the upper 16 bytes of each bank are common in

the PIC16F870/871 devices, temporary holding regis-

ters 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 con-

text save and restore. Example 11-1 can be used to

save and restore context for interrupts.

EXAMPLE 11-1: SAVING STATUS, W, AND PCLATH 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

MOVF

PCLATH, W

;Only required if using pages 1, 2 and/or 3

MOVWF

PCLATH_TEMP

;Save PCLATH into W

CLRF

PCLATH

;Page zero, regardless of current page

:(ISR)

MOVF

PCLATH_TEMP, W

;Restore PCLATH

MOVWF

PCLATH

;Move W into PCLATH

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

PIC16F870/P Datasheet(PDF) 100 Page - Microchip Technology

PIC16F870/P Datasheet(HTML) 100 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL