PIC16F7X7
15.15.1 INT INTERRUPT
15.15.3 PORTB INTCON CHANGE
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 on 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.
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.
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 by setting/clearing enable bit,
TMR0IE (INTCON<5>), see Section 6.0 “Timer0
Module”.
EXAMPLE 15-1:
SAVING STATUS AND W REGISTERS IN RAM
MOVWF
SWAPF
CLRF
MOVWF
:
W_TEMP
STATUS, W
STATUS
;Copy W to TEMP register
;Swap status to be saved into W
;bank 0, regardless of current bank, Clears IRP,RP1,RP0
;Save status to bank zero STATUS_TEMP register
STATUS_TEMP
:(ISR)
:
;Insert user code here
SWAPF
STATUS_TEMP, W
;Swap STATUS_TEMP register into W
;(sets bank to original state)
;Move W into STATUS register
;Swap W_TEMP
MOVWF
SWAPF
SWAPF
STATUS
W_TEMP, F
W_TEMP, W
;Swap W_TEMP into W
2004 Microchip Technology Inc.
DS30498C-page 185
MICROCHIP [ MICROCHIP ]
