INTEDG datasheet(133/478 Pages) MICROCHIP

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 2010-2012 Microchip Technology Inc.

DS41414D-page 133

PIC16(L)F1946/47

12.5

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 12-1 shows how to initialize an I/O port.

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 inputs

always read ‘0’.

12.5.1

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_REG

12.5.2

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.

12.5.3

PORTB FUNCTIONS AND OUTPUT

PRIORITIES

Each PORTB pin is multiplexed with other functions. The

pins, their combined functions and their output priorities

are shown in Table 12-5.

When multiple outputs are enabled, the actual pin

control goes to the peripheral with the highest priority.

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.

TABLE 12-5:

PORTB OUTPUT PRIORITY

Name

Function Priority(1)

RB0

SEG12 (LCD)

SRI (SR Latch)

RB0

RB1

SEG8 (LCD)

RB1

RB2

SEG9 (LCD)

RB2

RB3

SEG10 (LCD)

RB3

RB4

SEG11 (LCD)

RB4

RB5

SEG29 (LCD)

RB5

RB6

ICSPCLK (Programming)

ICDCLK (enabled by Configuration Word)

SEG38 (LCD)

RB6

RB7

ICSPDAT (Programming)

ICDDAT (enabled by Configuration Word)

SEG39 (LCD)

RB7

Note 1: Priority listed from highest to lowest.

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