PIC18F1230 MICROCHIP [Microchip Technology], PIC18F1230 Datasheet - Page 86

• Manufacturer Part Number: PIC18F1230
• Description: 18/20/28-Pin, Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F1230/1330
9.2
PORTB is an 8-bit wide, bidirectional port. The
corresponding data direction register is TRISB. Setting
a TRISB bit (= 1) will make the corresponding PORTB
pin an input (i.e., put the corresponding output driver in
a high-impedance mode). Clearing a TRISB bit (= 0)
will make the corresponding PORTB pin an output (i.e.,
put the contents of the output latch on the selected pin).
The Data Latch register (LATB) is also memory
mapped. Read-modify-write operations on the LATB
register read and write the latched output value for
PORTB.
EXAMPLE 9-2:
Each of the PORTB pins has a weak internal pull-up. A
single control bit can turn on all the pull-ups. This is
performed by clearing bit, RBPU (INTCON2<7>). The
weak pull-up is automatically turned off when the port
pin is configured as an output. The pull-ups are
disabled on a Power-on Reset.
DS39758B-page 84
CLRF
CLRF
MOVLW
MOVWF
MOVLW
MOVWF
Note:
PORTB, TRISB and LATB
Registers
PORTB
LATB
0Fh
ADCON1 ; digital I/O pins
0CFh
TRISB
On
configured as digital inputs except for RB2
and RB3.
RB2 and RB3 are configured as analog
inputs when the T1OSCMX bit of Configu-
ration Register 3H is cleared. Otherwise,
RB2 and RB3 are also configured as
digital inputs.
a
; Initialize PORTB by
; clearing output
; data latches
; Alternate method
; to clear output
; data latches
; Set RB<4:0> as
; (required if config bit
; PBADEN is set)
; Value used to
; initialize data
; direction
; Set RB<3:0> as inputs
; RB<5:4> as outputs
; RB<7:6> as inputs
Power-on Reset,
INITIALIZING PORTB
PORTB
Advance Information
is
Pins RB0, RB1 and RB4:RB7 are multiplexed with the
power control PWM outputs.
Pins RB2 and RB3 are multiplexed with external interrupt
inputs, interrupt-on-change input, the analog comparator
inputs and the Timer1 oscillator input and output to
become
RB3/INT3/KNBI3/CMP1/T1OSI respectively.
When the interrupt-on-change feature is enabled, only
pins configured as inputs can cause this interrupt to
occur (i.e., any RB2, RB3, RA0 and RA1 pin configured
as an output is excluded from the interrupt-on-change
comparison). The input pins (RB2, RB3, RA0 and RA1)
are compared with the old value latched on the last
read of PORTA and PORTB. The “mismatch” outputs of
these pins are ORed together to generate the RB Port
Change Interrupt with Flag bit, RBIF (INTCON<0>).
This interrupt can wake the device from Sleep mode, or
any of the Idle modes. The user, in the Interrupt Service
Routine, can clear the interrupt in the following manner:
a)
b)
A mismatch condition will continue to set flag bit, RBIF.
Reading PORTA and PORTB will end the mismatch
condition and allow flag bit, RBIF, to be cleared.
The interrupt-on-change feature is recommended for
wake-up on key depression operation and operations
where PORTA and PORTB are used for the interrupt-
on-change feature. Polling of PORTA and PORTB is
not recommended while using the interrupt-on-change
feature.
Any read or write of PORTA and/or PORTB
(except with the MOVFF (ANY), PORTA and
MOVFF (ANY), PORTB instructions).
Clear flag bit, RBIF.
RB2/INT2/KBI2/CMP2/T1OSO/T1CKI
© 2006 Microchip Technology Inc.
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