PIC12F609-ESLASHP datasheet(43/212 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS41302D-page 43

PIC12F609/615/617/12HV609/615

5.0

I/O PORT

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

available. Depending on 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.

5.1

GPIO and the TRISIO Registers

GPIO is a 6-bit wide port with 5 bidirectional and 1 input-

only pin. The corresponding data direction register is

TRISIO (Register 5-2). Setting a TRISIO bit (= 1) will

make the corresponding GPIO pin an input (i.e., disable

the output driver). Clearing a TRISIO bit (= 0) will make

the corresponding GPIO pin an output (i.e., enables

output driver and puts the contents of the output latch on

the selected pin). The exception is GP3, which is input

only and its TRIS bit will always read as ‘1’. Example 5-

1 shows how to initialize GPIO.

Reading the GPIO register (Register 5-1) 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

inputs. I/O pins configured as analog input always read

‘0’.

EXAMPLE 5-1:

INITIALIZING GPIO

Note:

GPIO = PORTA

TRISIO = TRISA

Note:

The ANSEL register must be initialized to

configure an analog channel as a digital

input. Pins configured as analog inputs will

read ‘0’ and cannot generate an interrupt.

BANKSEL

GPIO

;

CLRF

GPIO

;Init GPIO

BANKSEL

ANSEL

;

CLRF

ANSEL

;digital I/O, ADC clock

;setting ‘don’t care’

MOVLW

0Ch

;Set GP<3:2> as inputs

MOVWF

TRISIO

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

;as outputs

GPIO: GPIO REGISTER

U-0

R/W-x

R-x

R/W-x

—

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

= GPIO pin is > VIH

= GPIO pin is < VIL

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