INTEDG datasheet(145/478 Pages) MICROCHIP

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DS41414D-page 145

PIC16(L)F1946/47

12.13 PORTF Registers

PORTF is an 8-bit wide, bidirectional port. The

corresponding data direction register

is TRISF

(Register 12-21). Setting a TRISF bit (= 1) will make the

corresponding PORTF pin an input (i.e., put the

corresponding output driver in a High-Impedance mode).

Clearing a TRISF bit (= 0) will make the corresponding

PORTF pin an output (i.e., enable the output driver and

put the contents of the output latch on the selected pin).

Example 12-1 shows how to initialize an I/O port.

Reading the PORTF register (Register 12-13) 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 (LATF).

The TRISF register (Register 12-14) controls the

PORTF pin output drivers, even when they are being

used as analog inputs. The user should ensure the bits

in the TRISF register are maintained set when using

them as analog inputs. I/O pins configured as analog

inputs always read ‘0’.

12.13.1

ANSELF REGISTER

The ANSELF register (Register 12-23) is used to

configure the Input mode of an I/O pin to analog.

Setting the appropriate ANSELF 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 ANSELF bits has no effect 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.

12.13.2

PORTF FUNCTIONS AND OUTPUT

PRIORITIES

Each PORTF pin is multiplexed with other functions. The

pins, their combined functions and their output priorities

are shown in Table 12-13.

When multiple outputs are enabled, the actual pin

control goes to the peripheral with the highest priority.

Analog input and some digital input functions are not

included in the list below. These input functions can

remain active when the pin is configured as an output.

Certain digital input functions override other port

functions and are included in the priority list.

Note:

The ANSELF register must be initialized

to configure an analog channel as a digital

input. Pins configured as analog inputs

will read ‘0’.

TABLE 12-13: PORTF OUTPUT PRIORITY

Pin Name

Function Priority(1)

RF0

SEG41 (LCD)

RF0

RF1

C2OUT (Comparator)

SRNQ (SR Latch)

SEG19 (LCD)

RF1

RF2

C1OUT (Comparator)

SEG20 (LCD)

SRQ (SR Latch)

RF2

RF3

SEG21 (LCD)

RF3

RF4

SEG22 (LCD)

RF4

RF5

DACOUT (DAC)

SEG23 (LCD)

RF5

RF6

SEG24 (LCD)

RF6

RF7

SEG25 (LCD)

RF7

Note 1:

Priority listed from highest to lowest.

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