PIC16F722-ESLASHML datasheet(80/302 Pages) MICROCHIP

80 / 302 page

PIC16F72X/PIC16LF72X

DS41341E-page 80

6.5

PORTD and TRISD Registers

PORTD(1) is a 8-bit wide, bidirectional port. The

corresponding

data

direction

TRISD

(Register 6-13). 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 6-4 shows how to initialize PORTD.

Reading the PORTD register (Register 6-12) 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.

The TRISD register (Register 6-13) 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’.

EXAMPLE 6-4:

INITIALIZING PORTD

6.5.1

ANSELD REGISTER

The ANSELD register (Register 6-9) 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.

Note 1: PORTD is available on PIC16F724/LF724

and PIC16F727/LF727 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 ANSELD

CLRF

ANSELD

;Make PORTD digital

BANKSEL TRISD

;

MOVLW

B‘00001100’

;Set RD<3:2> as inputs

MOVWF

TRISD

;and set RD<7:4,1:0>

;as outputs

PORTD: PORTD REGISTER(1)

R/W-x

RD7

RD6

RD5

RD4

RD3

RD2

RD1

RD0

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 7-0

RD<7:0>: PORTD General Purpose I/O Pin bits

= Port pin is > VIH

= Port pin is < VIL

Note 1:

PORTD is not implemented on PIC16F722/723/726/PIC16LF722/723/726 devices, read as ‘0’.

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