PIC16LF1507 Datasheet, PDF (105/266 Pages) Microchip Technology – 20-Pin Flash, 8-Bit Microcontrollers

PIC16(L)F1507
11.3 PORTB Registers
PORTB is a 4-bit wide, bidirectional port. The
corresponding data direction register is TRISB
(Register 11-8). Setting a TRISB bit (= 1) will make the
corresponding PORTB pin an input (i.e., put the
corresponding output driver in a High-Impedance mode).
Clearing a TRISB bit (= 0) will make the corresponding
PORTB pin an output (i.e., enable the output driver and
put the contents of the output latch on the selected pin).
Example 11-1 shows how to initialize an I/O port.
Reading the PORTB register (Register 11-7) 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).
The TRISB register (Register 11-8) 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’.
11.3.1 ANSELB REGISTER
The ANSELB register (Register 11-10) 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 out-
put functions. A pin with TRIS clear and ANSELB set will
still operate as a digital output, but the Input mode will be
analog. This can cause unexpected behavior when exe-
cuting 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.
11.3.2
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 11-5.
When multiple outputs are enabled, the actual pin
control goes to the peripheral with the highest priority.
Analog input and some digital input functions are not
included in the output priority list. 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 the output priority list.
TABLE 11-5: PORTB OUTPUT PRIORITY
Pin Name
Function Priority⁽¹⁾
Note
RB4
RB4
RB5
RB5
RB6
RB6
RB7
RB7
1: Priority listed from highest to lowest.
2: Default pin (see APFCON register).
DS41586A-page 105
Preliminary
 2011 Microchip Technology Inc.