PIC18F4682T-I/ML【PDF 50/183 页】IC PIC MCU FLASH 40KX16 44QFN

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Sheet目录3871

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2011 Microchip Technology Inc.

DS39931D-page 143

PIC18F46J50 FAMILY

10.4

PORTC, TRISC and LATC

Registers

PORTC is an 8-bit wide, bidirectional port. The corre-

sponding Data Direction register is TRISC. Setting a

TRISC bit (= 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.,

put the contents of the output latch on the selected pin).

The Data Latch register (LATC) is also memory

mapped. Read-modify-write operations on the LATC

PORTC.

PORTC is multiplexed with several peripheral functions

(see Table 10-7). The pins have Schmitt Trigger input

buffers.

When enabling peripheral functions, care should be

taken in defining TRIS bits for each PORTC pin. Some

peripherals override the TRIS bit to make a pin an output,

while other peripherals override the TRIS bit to make a

pin an input. The user should refer to the corresponding

peripheral section for additional information.

Pins, RC4 and RC5, are multiplexed with the USB

module. Depending on the configuration of the module,

they can serve as the differential data lines for the on-

chip USB transceiver, or the data inputs from an external

USB transceiver. When used as general purpose inputs,

both RC4 and RC5 input buffers depend on the level of

the voltage applied to the VUSB pin, instead of VDD, like

all other general purpose I/O pins. Therefore, if the RC4

or RC5 general purpose input capability will be used, the

VUSB pin should not be left floating.

Unlike other PORTC pins, RC4 and RC5 do not have

TRISC bits associated with them. As digital ports, they

can only function as digital inputs. When configured for

USB operation, the data direction is determined by the

configuration and status of the USB module at a given

time. If an external transceiver is used, RC4 and RC5

always function as inputs from the transceiver. If the on-

chip transceiver is used, the data direction is determined

by the operation being performed by the module at that

time.

The contents of the TRISC register are affected by

peripheral overrides. Reading TRISC always returns

the current contents, even though a peripheral device

may be overriding one or more of the pins.

EXAMPLE 10-4:

INITIALIZING PORTC

Note:

On a Power-on Reset, PORTC pins

(except RC2, RC4 and RC5) are config-

ured as digital inputs. RC2 will default as

an analog input (controlled by the

ANCON1 register). To use pins, RC4 and

RC5, as digital inputs, the USB module

must be disabled (UCON<3> = 0) and the

on-chip USB transceiver must be dis-

abled (UCFG<3> = 1). The internal USB

transceiver has a POR value of enabled.

CLRF

LATC

; Initialize output data

; latch values for logic

; output low value.

MOVLB

0x0F

; ANCONx registers are

; not in access bank

;Configure RC2/AN11 for digital input mode

BSF

ANCON1, PCFG11, BANKED

;Disable USB transceiver to use RC4/RC5 as

;general purpose inputs

BCF

UCON, USBEN

;Disable USB module

BSF

UCFG, UTRDIS

;Disable USB transceiver

MOVLW

0x3F

; RC0 configured as digital input

MOVWF

TRISC

; RC1 configured as digital input

; RC2 configured as digital input

; RC4 configured as digital input

; RC5 configured as digital input

; RC6 configured as digital output

; RC7 configured as digital output

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