PIC16F882_12 datasheet(59/338 Pages) MICROCHIP

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 2006-2012 Microchip Technology Inc.

DS41291G-page 59

PIC16F882/883/884/886/887

3.6

PORTD and TRISD Registers

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

corresponding data direction register is TRISD

(Register 3-12). 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 3-5 shows how to initialize PORTD.

Reading the PORTD register (Register 3-11) 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 3-12) 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 3-5:

INITIALIZING PORTD

Note 1: PORTD is available on PIC16F884/887

only.

BANKSEL PORTD

;

CLRF

PORTD

;Init PORTD

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

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 bit

1 = Port pin is > VIH

0 = Port pin is < VIL

TRISD: PORTD TRI-STATE REGISTER

R/W-1

TRISD7

TRISD6

TRISD5

TRISD4

TRISD3

TRISD2

TRISD1

TRISD0

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

TRISD<7:0>: PORTD Tri-State Control bit

1 = PORTD pin configured as an input (tri-stated)

0 = PORTD pin configured as an output

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