PIC18FXX20
FIGURE 10-20:
PORTJ BLOCK DIAGRAM
IN I/O MODE
10.9 PORTJ, TRISJ and LATJ
Registers
Note: PORTJ is available only on PIC18F8X20
RD LATJ
devices.
Data
Bus
PORTJ is an 8-bit wide, bi-directional 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).
D
Q
I/O pin(1)
WR LATJ
or
CK
Data Latch
PORTJ
D
Q
Schmitt
Trigger
Input
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.
PORTJ is multiplexed with the system bus as the exter-
nal memory interface; I/O port functions are only avail-
able 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.
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 out-
put, 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.
WR TRISJ
CK
TRIS Latch
Buffer
RD TRISJ
Q
D
EN
EN
RD PORTJ
Note 1: I/O pins have diode protection to VDD and VSS.
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.
EXAMPLE 10-9:
INITIALIZING PORTJ
; Initialize PORTG by
; clearing output
; data latches
CLRF
PORTJ
CLRF
LATJ
; Alternate method
; to clear output
; data latches
MOVLW 0xCF
; Value used to
; initialize data
; direction
MOVWF TRISJ
; Set RJ3:RJ0 as inputs
; RJ5:RJ4 as output
; RJ7:RJ6 as inputs
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 125
MICROCHIP [ MICROCHIP ]
