PIC16F1946 Datasheet, PDF (128/440 Pages) Microchip Technology – 64-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt XLP Technology

PIC16F/LF1946/47
12.3 PORTB Registers
PORTB is an 8-bit wide, bidirectional port. The
corresponding data direction register is TRISB
(Register 12-7). 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., enable the output driver and
put the contents of the output latch on the selected pin).
Example 12-2 shows how to initialize PORTB.
Reading the PORTB register (Register 12-6) reads the
status of the pins, whereas writing to it will write to the
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then written
to the PORT data latch (LATB).
The TRISB register (Register 12-7) controls the PORTB
pin output drivers, even when they are being used as
analog inputs. The user should ensure the bits in the
TRISB register are maintained set when using them as
analog inputs. I/O pins configured as analog input always
read ‘0’.
12.3.1 WEAK PULL-UPS
Each of the PORTB pins has an individually configurable
internal weak pull-up. Control bits WPUB<7:0> enable or
disable each pull-up (see Register 12-9). Each weak
pull-up is automatically turned off when the port pin is
configured as an output. All pull-ups are disabled on a
Power-on Reset by the WPUEN bit of the OPTION
register.
12.3.2 INTERRUPT-ON-CHANGE
All of the PORTB pins are individually configurable as
an interrupt-on-change pin. Control bits IOCB<7:0>
enable or disable the interrupt function for each pin.
The interrupt-on-change feature is disabled on a
Power-on Reset. Reference Section 13.0
“Interrupt-On-Change” for more information.
EXAMPLE 12-2: INITIALIZING PORTB
BANKSEL
CLRF
BANKSEL
CLRF
BANKSEL
MOVLW
MOVWF
PORTDB;
PORTB
;Init PORTD
LATDB
;Data Latch
LATB
;
TRISD
;
B'11110000' ;Set RD<7:4> as inputs
TRISD
;and set RD<3:0> as
;outputs
12.3.3 PORTB FUNCTIONS AND OUTPUT
PRIORITIES
Each PORTB pin is multiplexed with other functions. The
pins, their combined functions and their output priorities
are briefly described here. For additional information,
refer to the appropriate section in this data sheet.
When multiple outputs are enabled, the actual pin
control goes to the peripheral with the lowest number in
the following lists.
Analog input and some digital input functions are not
included in the list below. These input functions can
remain active when the pin is configured as an output.
Certain digital input functions, such as the EUSART RX
signal, override other port functions and are included in
the priority list.
RB0
1. SEG30 (LCD)
2. FLT0 (CCP)
3. SRI (SR Latch)
4. INT
RB1
1. SEG8 (LCD)
RB2
1. SEG9 (LCD)
RB3
1. SEG10 (LCD)
RB4
1. SEG11 (LCD)
RB5
1. SEG29 (LCD)
2. T1G (TMR1)
RB6
1. ICSPCLK (Programming)
2. ICDCLK (enabled by Configuration Word)
3. SEG38 (LCD)
RB7
1. ICSPDAT (Programming)
2. ICDDAT (enabled by Configuration Word)
3. SEG39 (LCD)
DS41414A-page 126
Preliminary
 2010 Microchip Technology Inc.