PIC16F707-ESLASHML datasheet(65/284 Pages) MICROCHIP

65 / 284 page

 2010 Microchip Technology Inc.

Preliminary

DS41418A-page 65

PIC16F707/PIC16LF707

6.6

PORTE and TRISE Registers

PORTE is a 4-bit wide, bidirectional port. The

corresponding data direction register is TRISE. Setting a

TRISE bit (= 1) will make the corresponding PORTE pin

an input (i.e., put the corresponding output driver in a

High-Impedance mode). Clearing a TRISE bit (= 0) will

make the corresponding PORTE pin an output (i.e.,

enable the output driver and put the contents of the

output latch on the selected pin). The exception is RE3,

which is input only and its TRIS bit will always read as

‘1’. Example 6-5 shows how to initialize PORTE.

Reading the PORTE register (Register 6-16) 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. RE3 reads ‘0’ when

MCLRE = 1.

The TRISE register (Register 6-17) controls the PORTE

pin output drivers, even when they are being used as

analog inputs. The user should ensure the bits in the

TRISE register are maintained set when using them as

analog inputs. I/O pins configured as analog input always

read ‘0’.

EXAMPLE 6-5:

INITIALIZING PORTE

6.6.1

ANSELE REGISTER

The ANSELE register (Register 6-18) is used to

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

Setting the appropriate ANSELE 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 ANSELE bits has no affect on digital

output functions. A pin with TRIS clear and ANSELE

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:

The ANSELE register must be initialized to

configure an analog channel as a digital

input. Pins configured as analog inputs will

read ‘0’.

BANKSEL PORTE

;

CLRF

PORTE

;Init PORTE

BANKSEL ANSELE

;

CLRF

ANSELE

;digital I/O

BANKSEL TRISE

;

MOVLW

B‘00001100’ ;Set RE<2> as an input

MOVWF

TRISE

;and set RE<1:0>

;as outputs

PORTE: PORTE REGISTER

U-0

R-x

R/W-x

—

RE3

RE2

RE1

RE0

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 7-4

Unimplemented: Read as ‘0’

bit 3-0

RE<3:0>: PORTE I/O Pin bits

1 = Port pin is > VIH

0 = Port pin is < VIL

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