PIC16LC72A-04ESP 查看數據表（PDF） - Microchip Technology

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PIC16LC72A-04ESP

28-Pin 8-Bit CMOS Microcontrollers

Microchip Technology 

3.0 I/O PORTS

Some I/O port pins are multiplexed with an alternate

function 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.

Additional information on I/O ports may be found in the

PICmicro™ Mid-Range Reference Manual,

(DS33023).

3.1 PORTA and the TRISA Register

PORTA is a 6-bit wide bi-directional port. The corre-

sponding data direction register is TRISA. Setting a

TRISA bit (=1) will make the corresponding PORTA pin

an input, i.e., put the corresponding output driver in a

hi-impedance mode. Clearing a TRISA bit (=0) will

make the corresponding PORTA pin an output, (i.e., put

the contents of the output latch on the selected pin).

The PORTA register reads the state 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 the Timer0 module clock

input to become the RA4/T0CKI pin. The RA4/T0CKI

pin is a Schmitt Trigger input and an open drain output.

All other RA port pins have TTL input levels and full

CMOS output drivers.

Pin RA5 is multiplexed with the SSP to become the

RA5/SS pin.

On the PIC16C72A device, other PORTA pins are mul-

tiplexed with analog inputs and analog VREF input. The

operation of each pin is selected by clearing/setting the

control bits in the ADCON1 register (A/D Control

Register1).

Note:

On a Power-on Reset, pins with analog

functions are configured as analog inputs

with digital input buffers disabled . A digital

read of these pins will return ’0’.

The TRISA register controls the direction of the RA

pins, even when they are being used as analog inputs.

The user must ensure the bits in the TRISA register are

maintained set when using them as analog inputs.

PIC16C62B/72A

FIGURE 3-1: BLOCK DIAGRAM OF

RA3:RA0 AND RA5 PINS

Data

Bus

WR

Port

D

Q

CK Q

Data Latch

D

Q

VDD

P

N

I/O pin(1)

WR

TRIS

CK Q

TRIS Latch

RD TRIS

VSS

Analog

input

mode

(72A

only)

Q

D

TTL

input

buffer

EN

RD PORT

To A/D Converter (72A only)

Note 1: I/O pins have protection diodes to VDD and

VSS.

FIGURE 3-2: BLOCK DIAGRAM OF

RA4/T0CKI PIN

Data

Bus

WR

PORT

DQ

CK Q

Data Latch

N

I/O pin(1)

WR

TRIS

DQ

CK Q

TRIS Latch

VSS

Schmitt

Trigger

input

buffer

RD TRIS

QD

RD PORT

ENEN

TMR0 clock input

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

© 1999 Microchip Technology Inc.

Preliminary

DS35008B-page 19

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