PIC18F6525/6621/8525/8621
EXAMPLE 10-9:
INITIALIZING PORTJ
10.9 PORTJ, TRISJ and LATJ Registers
CLRF
PORTJ
; Initialize PORTG by
; clearing output
; data latches
Note:
PORTJ is available only on PIC18F8525/
8621 devices.
CLRF
LATJ
; Alternate method
; to clear output
; data latches
; Value used to
; initialize data
; direction
; Set RJ3:RJ0 as inputs
; RJ5:RJ4 as output
; RJ7:RJ6 as inputs
PORTJ is an 8-bit wide, bidirectional port. The corre-
sponding data direction register is TRISJ. Setting a
TRISJ bit (= 1) will make the corresponding PORTJ pin
an input (i.e., put the corresponding output driver in a
high-impedance mode). Clearing a TRISJ bit (= 0) will
make the corresponding PORTJ pin an output (i.e., put
the contents of the output latch on the selected pin).
MOVLW
MOVWF
0xCF
TRISJ
The Data Latch register (LATJ) is also memory
mapped. Read-modify-write operations on the LATJ
register, read and write the latched output value for
PORTJ.
FIGURE 10-21:
PORTJ BLOCK DIAGRAM
IN I/O MODE
PORTJ is multiplexed with the system bus as the
external memory interface; I/O port functions are only
available when the system bus is disabled. When
operating as the external memory interface, PORTJ
provides the control signal to external memory devices.
The RJ5 pin is not multiplexed with any system bus
functions.
RD LATJ
Data
Bus
D
Q
I/O pin(1)
WR LATJ
or
PORTJ
CK
Data Latch
When enabling peripheral functions, care should be
taken in defining TRIS bits for each PORTJ 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 corre-
sponding peripheral section for the correct TRIS bit
settings.
D
Q
Schmitt
Trigger
Input
WR TRISJ
CK
TRIS Latch
Buffer
RD TRISJ
Note:
On a Power-on Reset, these pins are
configured as digital inputs.
The pin override value is not loaded into the TRIS reg-
ister. This allows read-modify-write of the TRIS register
without concern due to peripheral overrides.
Q
D
EN
EN
RD PORTJ
Note 1: I/O pins have diode protection to VDD and VSS.
2005 Microchip Technology Inc.
DS39612B-page 125
MICROCHIP [ MICROCHIP ]
