PIC18F4550ESOSQTP datasheet(119/430 Pages) MICROCHIP

119 / 430 page

Preliminary

DS39632D-page 117

PIC18F2455/2550/4455/4550

10.3

PORTC, TRISC and LATC

Registers

PORTC is a 7-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).

In PIC18F2455/2550/4455/4550 devices, the RC3 pin

is not implemented.

The Data Latch register (LATC) is also memory

mapped. Read-modify-write operations on the LATC

PORTC.

PORTC is primarily multiplexed with serial communica-

tion modules, including the EUSART, MSSP module

and the USB module (Table 10-5). Except for RC4 and

RC5, PORTC uses Schmitt Trigger input buffers.

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. Both RC4 and RC5 have

TTL input buffers instead of the Schmitt Trigger buffers

on the other pins.

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.

When the external transceiver is enabled, RC2 also

serves as the output enable control to the transceiver.

Additional information on configuring USB options is

provided in Section 17.2.2.2 “External Transceiver”.

When enabling peripheral functions on PORTC pins

other than RC4 and RC5, care should be taken in defin-

ing the TRIS bits. 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

the correct TRIS bit settings.

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 10-3:

INITIALIZING PORTC

Note:

On a Power-on Reset, these pins, except

RC4 and RC5, are configured as digital

inputs. To use pins RC4 and RC5 as digi-

tal inputs, the USB module must be dis-

abled (UCON<3> = 0) and the on-chip

USB

transceiver

must

disabled

(UCFG<3> = 1).

CLRF

PORTC

; Initialize PORTC by

; clearing output

; data latches

CLRF

LATC

; Alternate method

; to clear output

; data latches

MOVLW

07h

; Value used to

; initialize data

; direction

MOVWF

TRISC

; RC<5:0> as outputs

; RC<7:6> as inputs

PIC18F4550ESOSQTP Datasheet(PDF) 119 Page - Microchip Technology

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