
2010 Microchip Technology Inc.
DS39774D-page 137
PIC18F85J11 FAMILY
11.5
PORTD, TRISD and
LATD Registers
PORTD is an 8-bit wide, bidirectional port. The corre-
sponding Data Direction and Output Latch registers are
TRISD and LATD. All pins on PORTD are digital only
and tolerate voltages up to 5.5V.
All pins on PORTD are implemented with Schmitt
Trigger input buffers. Each pin is individually
configurable as an input or output.
Each of the PORTD pins has a weak internal pull-up. A
single control bit can turn off all the pull-ups. This is
performed by clearing bit, RDPU (PORTG<7>). The
weak pull-up is automatically turned off when the port
pin is configured as an output. The pull-ups are
disabled on all device Resets.
On 80-pin devices, PORTD is multiplexed with the
system bus as part of the external memory interface.
I/O port and other functions are only available when the
interface is disabled, by setting the EBDIS bit
(MEMCON<7>). When the interface is enabled,
PORTD is the low-order byte of the multiplexed
address/data bus (AD<7:0>). The TRISD bits are also
overridden.
PORTD can also be configured to function as an 8-bit
wide, parallel microprocessor port by setting the
PSPMODE control bit (PSPCON<4>). In this mode,
parallel port data takes priority over other digital I/O (but
not the external memory interface). When the parallel
port is active, the input buffers are TTL. For more
EXAMPLE 11-4:
INITIALIZING PORTD
Note:
These pins are configured as digital inputs
on any device Reset.
CLRF
PORTD
; Initialize PORTD by
; clearing output
; data latches
CLRF
LATD
; Alternate method
; to clear output
; data latches
MOVLW
0CFh
; Value used to
; initialize data
; direction
MOVWF
TRISD
; Set RD<3:0> as inputs
; RD<5:4> as outputs
; RD<7:6> as inputs