16F1829 datasheet(138/420 Pages) MICROCHIP

138 / 420 page

PIC16F/LF1825/1829

DS41440A-page 138

Preliminary

 2010 Microchip Technology Inc.

12.4

PORTC Registers

PORTC is a 6-bit wide (8-bit wide for PIC16F/LF1829),

bidirectional port. The corresponding data direction

(= 1) will make the corresponding PORTC pin an input

(i.e., put the corresponding output driver in a

High-Impedance mode). Clearing a TRISC bit (= 0) will

make the corresponding PORTC pin an output (i.e.,

enable the output driver and put the contents of the

output latch on the selected pin). Example 12-2 shows

how to initialize PORTC.

Reading the PORTC register (Register 12-9) 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 (LATC).

The TRISC register (Register 12-10) controls the

PORTC pin output drivers, even when they are being

used as analog inputs. The user should ensure the bits in

the TRISC register are maintained set when using them

as analog inputs. I/O pins configured as analog input

always read ‘0’.

The INLVLC register (Register 12-20) controls the input

voltage threshold for each of the available PORTC

input pins. A selection between the Schmitt Trigger

CMOS or the TTL Compatible thresholds is available.

The input threshold is important in determining the

value of a read of the PORTC register and also the

level at which an Interrupt-on-Change occurs, if that

feature is enabled. See Section 30.4 “DC Character-

istics: PIC16F/LF1825/1829-I/E” for more information

on threshold levels.

12.4.1

ANSELC REGISTER

The ANSELC register (Register 12-12) is used to

configure the Input mode of an I/O pin to analog.

Setting the appropriate ANSELC 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 ANSELC bits has no affect on digital out-

put functions. A pin with TRIS clear and ANSELC 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.

EXAMPLE 12-3:

INITIALIZING PORTC

Note:

Changing the input threshold selection

should be performed while all peripheral

modules are disabled. Changing the

threshold level during the time a module is

active may inadvertently generate a tran-

sition associated with an input pin, regard-

less of the actual voltage level on that pin.

Note:

The ANSELC register must be initialized

to configure an analog channel as a digital

input. Pins configured as analog inputs

will read ‘0’.

BANKSEL PORTC

;

CLRF

PORTC

;Init PORTC

BANKSEL LATC

;Data Latch

CLRF

LATC

;

BANKSEL ANSELC

CLRF

ANSELC

;Make RC<5:0> digital

BANKSEL TRISC

;

MOVLW

B’00110000’;Set RC<5:4> as inputs

;and RC<3:0> as outputs

MOVWF

TRISC

;

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