PIC16F1938_13 Datasheet, PDF (139/488 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver

12.11 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 12-1 shows how to initialize an I/O port.
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.
Note: RE<2:0> and TRISE<2:0> pins are
available on PIC16(L)F1939 only.
12.11.1 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 effect 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’.
Note:
The ANSELE bits default to the Analog
mode after Reset. To use any pins as
digital general purpose or peripheral
inputs, the corresponding ANSEL bits
must be initialized to ‘0’ by user software.
PIC16(L)F1938/9
12.11.2 PORTE FUNCTIONS AND OUTPUT
PRIORITIES
Each PORTE pin is multiplexed with other functions. The
pins, their combined functions and their output priorities
are shown in Table 12-12.
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 priority list.
TABLE 12-12: PORTE OUTPUT PRIORITY
Pin Name
Function Priority⁽¹⁾
RE0
SEG21 (LCD)
CCP3/P3A (CCP)
RE0
RE1
SEG22 (LCD)
P3B (CCP)
RE1
RE2
SEG23 (LCD)
CCP5 (CCP)
RE2
Note 1: Priority listed from highest to lowest.
 2011-2013 Microchip Technology Inc.
DS40001574C-page 139