PIC16F1934-ESLASHML datasheet(142/508 Pages) MICROCHIP

142 / 508 page

PIC16F193X/LF193X

DS41364D-page 142

Preliminary

 2009 Microchip Technology Inc.

12.5

PORTD Registers

PORTD is a 8-bit wide, bidirectional port. The

corresponding data direction register is TRISD

(Register 12-14). Setting a TRISD bit (= 1) will make the

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

corresponding output driver in a High-Impedance mode).

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

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

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

Example 12-4 shows how to initialize PORTD.

Reading the PORTD register (Register 12-14) 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 (LATD).

The TRISD register (Register 12-15) controls the

PORTD pin output drivers, even when they are being

used as analog inputs. The user should ensure the bits

in the TRISD register are maintained set when using

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

input always read ‘0’.

12.5.1

ANSELD REGISTER

The ANSELD register (Register 12-17) is used to

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

Setting the appropriate ANSELD 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 ANSELD 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.

EXAMPLE 12-4:

INITIALIZING PORTD

12.5.2

PORTD FUNCTIONS AND OUTPUT

PRIORITIES

Each PORTD pin is multiplexed with other functions. The

pins, their combined functions and their output priorities

are briefly described here. For additional information,

refer to the appropriate section in this data sheet.

When multiple outputs are enabled, the actual pin

control goes to the peripheral with the lowest number in

the following lists.

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.

RD0

COM3 (LCD)

RD0

RD1

CCP4 (CCP)

RD1

RD2

P2B (CCP)

RD2

RD3

SEG16 (LCD)

P2C (CCP)

RD3

RD4

SEG17 (LCD)

P2D (CCP)

RD4

RD5

SEG18 (LCD)

P1B (CCP)

RD5

RD6

SEG19 (LCD)

P1C (CCP)

RD6

RD7

SEG20 (LCD)

P1D (CCP)

RD7

Note:

PORTD is available on PIC16F1936 and

PIC16F1938 only.

Note:

The ANSELD register must be initialized

to configure an analog channel as a digital

input. Pins configured as analog inputs will

read ‘0’.

BANKSEL

PORTD

;

CLRF

PORTD

;Init PORTD

BANKSEL

LATD

;Data Latch

CLRF

LATD

;

BANKSEL

ANSELD

;

CLRF

ANSELD

;digital I/O

BANKSEL

TRISD

;

MOVLW

B'11110000' ;Set RD<7:4> as inputs

MOVWF

TRISD

;and set RD<3:0> as

;outputs

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