PIC16F84A datasheet(51/337 Pages) MICROCHIP

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DS30234D-page 51

PIC16C6X

5.0

I/O PORTS

Some pins for these I/O ports are multiplexed with an

alternate function(s) for the peripheral features on the

device. In general, when a peripheral is enabled, that

pin may not be used as a general purpose I/O pin.

5.1

PORTA and TRISA Register

All devices have a 6-bit wide PORTA, except for the

PIC16C61 which has a 5-bit wide PORTA.

Pin RA4/T0CKI is a Schmitt Trigger input and an open

drain output. All other RA port pins have TTL input lev-

els and full CMOS output drivers. All pins have data

direction bits (TRIS registers) which can conﬁgure

these pins as output or input.

Setting a bit in the TRISA register puts the correspond-

ing output driver in a hi-impedance mode. Clearing a bit

in the TRISA register puts the contents of the output

latch on the selected pin.

Reading PORTA register reads the status of the pins

whereas writing to it will write to the port latch. All write

operations are read-modify-write operations. There-

fore, a write to a port implies that the port pins are read,

this value is modiﬁed, and then written to the port data

latch.

Pin RA4 is multiplexed with Timer0 module clock input

to become the RA4/T0CKI pin.

EXAMPLE 5-1:

INITIALIZING PORTA

BCF

STATUS, RP0

;

BCF

STATUS, RP1

; PIC16C66/67 only

CLRF

PORTA

; Initialize PORTA by

; clearing output

; data latches

BSF

STATUS, RP0

; Select Bank 1

MOVLW

0xCF

; Value used to

; initialize data

; direction

MOVWF

TRISA

; Set RA<3:0> as inputs

; RA<5:4> as outputs

; TRISA<7:6> are always

; read as '0'.

Applicable Devices

61 62 62A R62 63 R63 64 64A R64 65 65A R65 66 67

Applicable Devices

61 62 62A R62 63 R63 64 64A R64 65 65A R65 66 67

FIGURE 5-1:

BLOCK DIAGRAM OF THE

RA3:RA0 PINS AND THE RA5

FIGURE 5-2:

BLOCK DIAGRAM OF THE

RA4/T0CKI PIN

Data

bus

Port

TRIS

Data Latch

TRIS Latch

RD TRIS

RD PORT

TTL

input

buffer

VSS

VDD

I/O pin(1)

Note 1:

I/O pins have protection diodes to VDD and

VSS.

The PIC16C61 does not have an RA5 pin.

Data

bus

PORT

TRIS

RD PORT

Data Latch

TRIS Latch

RD TRIS

Schmitt

Trigger

input

buffer

VSS

I/O pin(1)

TMR0 clock input

Note 1: I/O pin has protection diodes to VSS only.

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