12F615 datasheet(34/168 Pages) MICROCHIP

34 / 168 page

PIC12F609/615/12HV609/615

DS41302A-page 32

Preliminary

4.2

Additional Pin Functions

Every GPIO pin on the PIC12F609/615/12HV609/615

has an interrupt-on-change option and a weak pull-up

option. The next three sections describe these

functions.

4.2.1

ANSEL REGISTER

The ANSEL register is used to configure the Input

mode of an I/O pin to analog. Setting the appropriate

ANSEL bit high will cause all digital reads on the pin to

be read as ‘0’ and allow analog functions on the pin to

operate correctly.

The state of the ANSEL bits has no affect on digital

output functions. A pin with TRIS clear and ANSEL set

will still operate as a digital output, but the Input mode

will be analog. This can cause unexpected behavior

when executing read-modify-write instructions on the

affected port.

4.2.2

WEAK PULL-UPS

Each of the GPIO pins, except GP3, has an individually

configurable internal weak pull-up. Control bits WPUx

enable or disable each pull-up. Refer to Register 4-5.

Each weak pull-up is automatically turned off when the

port pin is configured as an output. The pull-ups are

disabled on a Power-on Reset by the GPPU bit of the

OPTION register). A weak pull-up is automatically

enabled for GP3 when configured as MCLR and

disabled when GP3 is an I/O. There is no software

control of the MCLR pull-up.

4.2.3

INTERRUPT-ON-CHANGE

Each GPIO pin is individually configurable as an inter-

rupt-on-change pin. Control bits IOCx enable or disable

the interrupt function for each pin. Refer to Register 4-6.

The interrupt-on-change is disabled on a Power-on

Reset.

For enabled interrupt-on-change pins, the values are

compared with the old value latched on the last read of

GPIO. The ‘mismatch’ outputs of the last read are OR’d

together to set the GPIO Change Interrupt Flag bit

(GPIF) in the INTCON register (Register 2-3).

This interrupt can wake the device from Sleep. The

user, in the Interrupt Service Routine, clears the inter-

rupt by:

Any read of GPIO AND Clear flag bit GPIF. This

will end the mismatch condition;

Any write of GPIO AND Clear flag bit GPIF will

end the mismatch condition;

A mismatch condition will continue to set flag bit GPIF.

Reading GPIO will end the mismatch condition and

allow flag bit GPIF to be cleared. The latch holding the

last read value is not affected by a MCLR nor BOR

Reset. After these resets, the GPIF flag will continue to

be set if a mismatch is present.

Note:

If a change on the I/O pin should occur

when

any

GPIO

operation

being

executed, then the GPIF interrupt flag may

not get set.

12F615 Datasheet(PDF) 34 Page - Microchip Technology

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