PIC16F193X datasheet(91/418 Pages) MICROCHIP

91 / 418 page

Preliminary

DS41364A-page 89

PIC16F193X/LF193X

6.3

PORTB and TRISB Registers

PORTB is an 8-bit wide, bidirectional port. The

corresponding

data

direction

TRISB

(Register 6-9). 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 6-2 shows how to initialize PORTB.

Reading the PORTB register (Register 6-6) 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.

The TRISB register (Register 6-9) 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’. Example 6-2 shows how to initialize PORTB.

EXAMPLE 6-2:

INITIALIZING PORTB

6.3.1

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 6-8). 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

6.3.2

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 7.0 “Interrupt-On-Change”

for more information.

Note:

The ANSELB register must be initialized to

configure an analog channel as a digital

input. Pins configured as analog inputs will

read ‘0’.

BANKSEL PORTB

;

CLRF

PORTB

;Init PORTB

BANKSEL ANSELB

CLRF

ANSELB

;Make RB<7:0> digital

BANKSEL TRISB

;

MOVLW

’11110000’ ;Set RB<7:4> as inputs

;and RB<3:0> as outputs

MOVWF

TRISB

;

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