PIC16LF1946_13 Datasheet, PDF (130/478 Pages) Microchip Technology – 64-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt XLP Technology

PIC16(L)F1946/47
12.3 PORTA Registers
PORTA is an 8-bit wide, bidirectional port. The
corresponding data direction register is TRISA
(Register 12-3). Setting a TRISA bit (= 1) will make the
corresponding PORTA pin an input (i.e., disable the
output driver). Clearing a TRISA bit (= 0) will make the
corresponding PORTA pin an output (i.e., enables
output driver and puts the contents of the output latch
on the selected pin). Example 12-1 shows how to
initialize PORTA.
Reading the PORTA register (Register 12-2) 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 (LATA).
The TRISA register (Register 12-3) controls the
PORTA pin output drivers, even when they are being
used as analog inputs. The user should ensure the bits
in the TRISA register are maintained set when using
them as analog inputs. I/O pins configured as analog
input always read ‘0’.
12.3.1 ANSELA REGISTER
The ANSELA register (Register 12-5) is used to
configure the Input mode of an I/O pin to analog.
Setting the appropriate ANSELA 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 ANSELA 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.
Note:
The ANSELA 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.
12.3.2 PORTA FUNCTIONS AND OUTPUT
PRIORITIES
Each PORTA pin is multiplexed with other functions. The
pins, their combined functions and their output priorities
are shown in Table 12-2.
When multiple outputs are enabled, the actual pin
control goes to the peripheral with the highest priority.
Analog input functions, such as ADC, comparator and
CapSense inputs, are not shown in the priority lists.
These inputs are active when the I/O pin is set for
Analog mode using the ANSELx registers. Digital
output functions may control the pin when it is in Analog
mode with the priority list.
TABLE 12-2: PORTA OUTPUT PRIORITY
Pin
Name
Function Priority⁽¹⁾
RA0 SEG33 (LCD)
RA0
RA1 SEG18
RA1
RA2 SEG34 (LCD)
RA2
RA3 SEG35 (LCD)
RA3
RA4 SEG14 (LCD)
RA4
RA5 SEG15 (LCD)
RA5
RA6 OSC2 (enabled by Configuration Word)
CLKOUT (enabled by Configuration Word)
SEG36 (LCD)
RA6
RA7 OSC1/CLKIN (enabled by Configuration
Word)
SEG37 (LCD)
RA7
Note 1: Priority listed from highest to lowest.
DS41414D-page 130
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