Microchip Technology GPIODM-KPLCD Data Sheet
© 2009 Microchip Technology Inc.
DS39632E-page 119
PIC18F2455/2550/4455/4550
10.3
PORTC, TRISC and LATC
Registers
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).
The RC3 pin is not implemented in these devices.
The Data Latch register (LATC) is also memory
mapped. Read-modify-write operations on the LATC
register read and write the latched output value for
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”.
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 RC3 pin is not implemented in these devices.
The Data Latch register (LATC) is also memory
mapped. Read-modify-write operations on the LATC
register read and write the latched output value for
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.
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.
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
digital inputs, the USB module must be
disabled (UCON<3> = 0) and the on-chip
USB transceiver must be disabled
(UCFG<3> = 1).
RC4 and RC5, are configured as digital
inputs. 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 disabled
(UCFG<3> = 1).
CLRF
PORTC
; Initialize PORTC by
; clearing output
; data latches
; clearing output
; data latches
CLRF
LATC
; Alternate method
; to clear output
; data latches
; to clear output
; data latches
MOVLW
07h
; Value used to
; initialize data
; direction
; initialize data
; direction
MOVWF
TRISC
; RC<5:0> as outputs
; RC<7:6> as inputs
; RC<7:6> as inputs