PIC16F1934-ESLASHML datasheet(145/508 Pages) MICROCHIP

145 / 508 page

 2009 Microchip Technology Inc.

Preliminary

DS41364D-page 145

PIC16F193X/LF193X

12.6

PORTE 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 12-5 shows how to initialize PORTE.

Reading the PORTE register (Register 12-18) 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

(LATE). RE3 reads ‘0’ when MCLRE = 1.

12.6.1

ANSELE REGISTER

The ANSELE register (Register 12-21) 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 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.

The TRISE register (Register 12-19) 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 12-5:

INITIALIZING PORTE

12.6.2

PORTE FUNCTIONS AND OUTPUT

PRIORITIES

Each PORTE 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, such as the EUSART RX

signal, override other port functions and are included in

the priority list.

RE0

SEG21 (LCD)

CCP3/P3A (CCP)

RE0

RE1

SEG22 (LCD)

P3B (CCP)

RE1

RE2

SEG23 (LCD)

CCP5 (CCP)

RE2

Note:

RE<2:0> and TRISE<2:0> pins are

available on PIC16F1936 and PIC16F1938

only.

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

LATE

;Data Latch

CLRF

LATE

;

BANKSEL ANSELE

;

CLRF

ANSELE

;digital I/O

BANKSEL TRISE

;

MOVLW

B‘00001100’

;Set RE<3:2> as inputs

MOVWF

TRISE

;and set RE<1:0>

;as outputs

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