PIC16F570 datasheet(27/134 Pages) MICROCHIP

27 / 134 page

 2012-2014 Microchip Technology Inc.

DS40001652C-page 27

PIC16F527

6.0

I/O PORT

As with any other register, the I/O register(s) can be

written and read under program control. However, read

instructions (e.g., MOVF PORTB,W) always read the I/O

pins independent of the pin’s Input/Output modes. On

Reset, all I/O ports are defined as input (inputs are at high-

impedance) since the I/O control registers are all set.

6.1

PORTA

PORTA is a 6-bit I/O register. Only the low-order six

bits are used (RA<5:0>). Bits 7 and 6 are

unimplemented and read as ‘0’s. Please note that RA3

is an input-only pin. The Configuration Word can set

several I/Os to alternate functions. When acting as

alternate functions, the pins will read as ‘0’ during a

port read. Pins RA0, RA1, RA3 and RA4 can be

configured with weak pull-ups and also for wake-up on

change. The wake-up on change and weak pull-up

functions are not pin selectable. If RA3/MCLR is

configured as MCLR, weak pull-up is always on and

wake-up on change for this pin is not enabled.

6.2

PORTB

PORTB is a 4-bit I/O register. Only the high-order four

bits are used (RB<7:4>). Bits 0 through 3 are

unimplemented and read as ‘0’s.

6.3

PORTC

PORTC is an 8-bit I/O register.

6.4

TRIS Register

The Output Driver Control register is loaded with the

contents of the W register by executing the TRIS

instruction. A ‘1’ from a TRIS register bit puts the

corresponding output driver in a High-Impedance

mode. A ‘0’ puts the contents of the output data latch

on the selected pins, enabling the output buffer. The

exceptions are RA3, which is input-only and the T0CKI

pin, which may be controlled by the OPTION register

(see Register 4-2).

TRIS registers are “write-only”. Active bits in these

registers are set (output drivers disabled) upon Reset.

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