PIC18F1XK22 Datasheet, PDF (80/388 Pages) Microchip Technology – 20-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC18F1XK22/LF1XK22
This interrupt can wake the device from the Sleep mode,
or any of the Idle modes. The user, in the Interrupt
Service Routine, can clear the interrupt in the following
manner:
a) Any read or write of PORTA to clear the mis-
match condition (except when PORTA is the
source or destination of a MOVFF instruction).
b) Clear the flag bit, RABIF.
A mismatch condition will continue to set the RABIF flag
bit. Reading or writing PORTA will end the mismatch
condition and allow the RABIF bit to be cleared. The latch
holding the last read value is not affected by a MCLR nor
Brown-out Reset. After either one of these Resets, the
RABIF flag will continue to be set if a mismatch is present.
Note 1: If a change on the I/O pin should occur
when the read operation is being exe-
cuted (start of the Q2 cycle), then the
RABIF interrupt flag may not get set. Fur-
thermore, since a read or write on a port
affects all bits of that port, care must be
taken when using multiple pins in Inter-
rupt-on-change mode. Changes on one
pin may not be seen while servicing
changes on another pin.
The interrupt-on-change feature is recommended for
wake-up on key depression operation and operations
where PORTA is only used for the interrupt-on-change
feature. Polling of PORTA is not recommended while
using the interrupt-on-change feature.
Each of the PORTA pins has an individually controlled
weak internal pull-up. When set, each bit of the WPUA
register enables the corresponding pin pull-up. When
cleared, the RABPU bit of the INTCON2 register
enables pull-ups on all pins which also have their cor-
responding WPUA bit set. When set, the RABPU bit
disables all weak pull-ups. The weak pull-up is auto-
matically turned off when the port pin is configured as
an output. The pull-ups are disabled on a Power-on
Reset.
RA3 is an input only pin. Its operation is controlled by
the MCLRE bit of the CONFIG3H register. When
selected as a port pin (MCLRE = 0), it functions as a
digital input only pin; as such, it does not have TRIS or
LAT bits associated with its operation.
Note:
On a Power-on Reset, RA3 is enabled as
a digital input only if Master Clear
functionality is disabled.
Pins RA4 and RA5 are multiplexed with the main oscil-
lator pins; they are enabled as oscillator or I/O pins by
the selection of the main oscillator in the Configuration
register (see Section 22.1 “Configuration Bits” for
details). When they are not used as port pins, RA4 and
RA5 and their associated TRIS and LAT bits read as
‘0’.
RA<4,2:0> are pins multiplexed with analog inputs. The
operation of pins RA<4,2:0> as analog are selected by
setting the ANS<3:0> bits in the ANSEL register, which
is the default setting after a Power-on Reset.
EXAMPLE 8-1: INITIALIZING PORTA
CLRF
CLRF
MOVLW
MOVWF
PORTA
LATA
030h
TRISA
; Initialize PORTA by
; clearing output
; data latches
; Alternate method
; to clear output
; data latches
; Value used to
; initialize data
; direction
; Set RA<5:4> as output
DS41365D-page 80
Preliminary
 2010 Microchip Technology Inc.