PIC12F752 datasheet(45/204 Pages) MICROCHIP

45 / 204 page

 2011 Microchip Technology Inc.

Preliminary

DS41576A-page 45

PIC12F752/HV752

5.0

I/O PORTS

For this device there is one port available, PORTA. In

general, when a peripheral is enabled on a port pin,

that pin cannot be used as a general purpose output.

However, the pin can still be read.

PORTA has three standard registers for its operation.

These registers are:

• TRISA registers (data direction)

• PORTA registers (reads the levels on the pins of

the device)

• LATA registers (output latch)

Some ports may have one or more of the following

additional registers. These registers are:

• ANSELA (analog select)

• WPUA (weak pull-up)

The Data Latch (LATA register) is useful for read-

modify-write operations on the value that the I/O pins

are driving.

A write operation to the LATA register has the same

effect as a write to the corresponding PORTA register.

A read of the LATA register reads the values held in the

I/O PORT latches, while a read of the PORTA register

reads the actual I/O pin value.

Ports that support analog inputs have an associated

ANSEL register. When an ANSELA bit is set, the digital

input buffer associated with that bit is disabled.

Disabling the input buffer prevents analog signal levels

on the pin between a logic high and low from causing

excessive current in the logic input circuitry. A

simplified model of a generic I/O port, without the

interfaces to other peripherals, is shown in Figure 5-1.

FIGURE 5-1:

GENERIC I/O PORTA

OPERATION

EXAMPLE 5-1:

INITIALIZING PORTA

Write LATA

Data Register

I/O pin

Read PORTA

Write PORTA

TRISA

Read LATA

Data Bus

To peripherals

ANSELA

VDD

VSS

; This code example illustrates

; initializing the PORTA register. The

; other ports are initialized in the same

; manner.

BANKSEL

PORTA

;

CLRF

PORTA

;Init PORTA

BANKSEL

LATA

;Data Latch

CLRF

LATA

;

BANKSEL

ANSELA

;

CLRF

ANSELA

;digital I/O

BANKSEL

TRISA

;

MOVLW

B'00111000'

;Set RA<5:3> as inputs

MOVWF

TRISA

;and set RA<2:0> as

;outputs

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