Datasheet

 2010-2013 Microchip Technology Inc. DS40001452D-page 113
PIC16(L)F1516/7/8/9
12.3 PORTB Registers
12.3.1 DATA REGISTER
PORTB is a 8-bit wide, bidirectional port. The
corresponding data direction register is TRISB
(Register 12-7). 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 12-1 shows how to initialize an I/O port.
Reading the PORTB register (Register 12-6) 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).
12.3.2 DIRECTION CONTROL
The TRISB register (Register 12-7) 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’.
12.3.3 ANALOG CONTROL
The ANSELB register (Register 12-9) 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.
12.3.4 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 12-5.
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 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 the priority list.
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.
TABLE 12-5: PORTB OUTPUT PRIORITY
Pin Name Function Priority
(1)
RB0 RB0
RB1 RB1
RB2 RB2
RB3 CCP2
RB3
RB4 RB4
RB5 RB5
RB6 ICDCLK
RB6
RB7 ICDDAT
RB7
Note 1: Priority listed from highest to lowest.