PIC12F683-ISLASHP datasheet(33/176 Pages) MICROCHIP

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DS41211D-page 31

PIC12F683

4.0

GPIO PORT

There are as many as six general purpose I/O pins

available.

Depending

which

peripherals

are

enabled, some or all of the pins may not be available as

general purpose I/O. In general, when a peripheral is

enabled, the associated pin may not be used as a

general purpose I/O pin.

4.1

GPIO and the TRISIO Registers

GPIO

6-bit

wide,

bidirectional

port.

The

corresponding data direction register is TRISIO.

Setting a TRISIO bit (= 1) will make the corresponding

GPIO pin an input (i.e., put the corresponding output

driver in a High-Impedance mode). Clearing a TRISIO

bit (= 0) will make the corresponding GPIO pin an

output (i.e., put the contents of the output latch on the

selected pin). An exception is GP3, which is input only

and its TRISIO bit will always read as ‘1’. Example 4-1

shows how to initialize GPIO.

Reading the GPIO 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.

Therefore, a write to a port implies that the port pins are

read, this value is modified and then written to the

PORT data latch. GP3 reads ‘0’ when MCLRE = 1.

The TRISIO register controls the direction of the GPIO

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

The user must ensure the bits in the TRISIO register

are maintained set when using them as analog inputs.

I/O pins configured as analog input always read ‘0’.

EXAMPLE 4-1:

INITIALIZING GPIO

Note:

The ANSEL and CMCON0 registers must

be initialized to configure an analog

channel as a digital input. Pins configured

as analog inputs will read ‘0’.

BANKSEL

GPIO

;

CLRF

GPIO

;Init GPIO

MOVLW

07h

;Set GP<2:0> to

MOVWF

CMCON0

;digital I/O

BANKSEL

ANSEL

;

CLRF

ANSEL

;digital I/O

MOVLW

0Ch

;Set GP<3:2> as inputs

MOVWF

TRISIO

;and set GP<5:4,1:0>

;as outputs

GPIO: GENERAL PURPOSE I/O REGISTER

U-0

R/W-x

R/W-0

R-x

R/W-0

—

GP5

GP4

GP3

GP2

GP1

GP0

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7-6

Unimplemented: Read as ‘0’

bit 5-0

GP<5:0>: GPIO I/O Pin bit

= Port pin is > VIH

= Port pin is < VIL

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