PIC16C712 datasheet(23/108 Pages) MICROCHIP

23 / 108 page

PIC16C712/716

Preliminary

DS41106A-page 23

3.2

PORTB and the TRISB Register

PORTB is an 8-bit wide bi-directional port. The corre-

sponding 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

hi-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).

EXAMPLE 3-1:

INITIALIZING PORTB

BCF

STATUS, RP0

;

CLRF

PORTB

; Initialize PORTB by

; clearing output

; data latches

BSF

STATUS, RP0

; Select Bank 1

MOVLW

0xCF

; Value used to

; initialize data

; direction

MOVWF

TRISB

; Set RB<3:0> as inputs

; RB<5:4> as outputs

; RB<7:6> as inputs

Each of the PORTB pins has a weak internal pull-up. A

single control bit can turn on all the pull-ups. This is per-

formed by clearing bit RBPU (OPTION_REG<7>). The

weak pull-up is automatically turned off when the port

pin is configured as an output. The pull-ups are dis-

abled on a Power-on Reset.

FIGURE 3-3:

BLOCK DIAGRAM OF RB0 PIN

Data Latch

RBPU(1)

VDD

DATA BUS

WR PORT

WR TRIS

RD TRIS

RD PORT

weak

pull-up

RD PORT

RB0/INT

I/O

TTL

Input

Buffer

Schmitt Trigger

Buffer

TRIS Latch

Note 1:

To enable weak pull-ups, set the appropriate TRIS bit(s) and clear the RBPU bit (OPTION_REG<7>).

VSS

VDD

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