PIC18F6525/6621/8525/8621
FIGURE 10-9:
PORTD BLOCK DIAGRAM
IN I/O PORT MODE
10.4 PORTD, TRISD and LATD
Registers
PORTD is an 8-bit wide, bidirectional port. The corre-
sponding data direction register is TRISD. Setting a
TRISD bit (= 1) will make the corresponding PORTD
pin an input (i.e., put the corresponding output driver in
a high-impedance mode). Clearing a TRISD bit (= 0)
will make the corresponding PORTD pin an output (i.e.,
put the contents of the output latch on the selected pin).
RD LATD
Data
Bus
D
Q
WR LATD
or
PORTD
I/O pin(1)
CK
Data Latch
The Data Latch register (LATD) is also memory
mapped. Read-modify-write operations on the LATD
register, read and write the latched output value for
PORTD.
D
Q
Schmitt
Trigger
Input
WR TRISD
RD TRISD
CK
TRIS Latch
Buffer
PORTD is an 8-bit port with Schmitt Trigger input
buffers. Each pin is individually configurable as an input
or output.
Note:
On a Power-on Reset, these pins are
configured as digital inputs.
Q
D
PORTD is multiplexed with the system bus as the
external memory interface. I/O port functions are only
available when the system bus is disabled by setting
the EBDIS bit in the MEMCOM register
(MEMCON<7>). When operating as the external
memory interface, PORTD is the low-order byte of the
multiplexed address/data bus (AD7:AD0).
EN
EN
RD PORTD
Note 1: I/O pins have diode protection to VDD and VSS.
PORTD can also be configured as an 8-bit wide
microprocessor port (Parallel Slave Port) by setting
control bit PSPMODE (TRISE<4>). In this mode, the
input buffers are TTL. See Section 10.10 “Parallel
Slave Port” for additional information on the Parallel
Slave Port (PSP).
EXAMPLE 10-4:
INITIALIZING PORTD
CLRF
PORTD
; Initialize PORTD by
; clearing output
; data latches
CLRF
LATD
; Alternate method
; to clear output
; data latches
MOVLW
MOVWF
0xCF
; Value used to
; initialize data
; direction
; Set RD<3:0> as inputs
; RD<5:4> as outputs
; RD<7:6> as inputs
TRISD
2005 Microchip Technology Inc.
DS39612B-page 111
MICROCHIP [ MICROCHIP ]
