PIC16F1516 datasheet(119/344 Pages) MICROCHIP

119 / 344 page

 2010 Microchip Technology Inc.

Preliminary

DS41452B-page 119

PIC16(L)F1516/7/8/9

12.3

PORTB Registers

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).

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’.

12.3.1

ANSELB REGISTER

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 affect 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.

12.3.2

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 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 Table 12-5.

Note:

The ANSELB register must be initialized

to configure an analog channel as a digital

input. Pins configured as analog inputs

will read ‘0’.

TABLE 12-5:

PORTB OUTPUT PRIORITY

Pin Name

Function Priority(1)

RB0

RB1

RB2

RB3

CCP2

RB3

RB4

RB5

RB6

ICDCLK

RB6

RB7

ICDDAT

RB7

Note 1:

Priority listed from highest to lowest.

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