PIC16LF1454 Datasheet, PDF (135/418 Pages) Microchip Technology – 14/20-Pin Flash, 8-Bit USB Microcontrollers with XLP Technology

12.5 PORTB Registers
(PIC16(L)F1455/9 only)
12.5.1 DATA REGISTER
PORTB is a 4-bit wide, bidirectional port. The
corresponding data direction register is TRISB
(Register 12-3). Setting a TRISB bit (= 1) will make the
corresponding PORTB pin an input (i.e., disable the
output driver). Clearing a TRISB bit (= 0) will make the
corresponding PORTB pin an output (i.e., enables
output driver and puts the contents of the output latch
on the selected pin). Example 12-2 shows how to
initialize an I/O port.
Reading the PORTB 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 (LATB).
12.5.2 DIRECTION CONTROL
The TRISB register (Register 12-3) controls the
PORTB pin output drivers, even when they are being
used as analog inputs. The user should ensure the bits
in the TRISB register are maintained set when using
them as analog inputs. I/O pins configured as analog
input always read ‘0’.
12.5.3 ANALOG CONTROL
The ANSELB register (Register 12-5) is used to
configure the Input mode of an I/O pin to analog.
Setting the appropriate ANSELB 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 ANSELB 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 ANSELB 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)F1454/5/9
12.5.4 PORTB FUNCTIONS AND OUTPUT
PRIORITIES
Each PORTB 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 and comparator
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 shown below in Table 12-2.
TABLE 12-5: PORTB OUTPUT PRIORITY
Pin Name
Function Priority⁽¹⁾
RB4
SDA
RB4
RB5
RX
RB5
RB6
SCL
SCK
RB6
RB7
TX
RB7
Note 1: Priority listed from highest to lowest.
2: Default pin (see APFCON register).
3: Alternate pin (see APFCON register).
 2012 Microchip Technology Inc.
Preliminary
DS41639A-page 135