Datasheet
PIC18F6520/8520/6620/8620/6720/8720
DS39609C-page 122 2003-2013 Microchip Technology Inc.
10.8 PORTH, LATH and TRISH
Registers
PORTH is an 8-bit wide, bidirectional I/O port. The cor-
responding data direction register is TRISH. Setting a
TRISH bit (= 1) will make the corresponding PORTH
pin an input (i.e., put the corresponding output driver in
a high-impedance mode). Clearing a TRISH bit (= 0)
will make the corresponding PORTH pin an output (i.e.,
put the contents of the output latch on the selected pin).
Read-modify-write operations on the LATH register,
read and write the latched output value for PORTH.
Pins RH7:RH4 are multiplexed with analog inputs
AN15:AN12. Pins RH3:RH0 are multiplexed with the
system bus as the external memory interface; they are
the high-order address bits, A19:A16. By default, pins
RH7:RH4 are enabled as A/D inputs and pins
RH3:RH0 are enabled as the system address bus.
Register ADCON1 configures RH7:RH4 as I/O or A/D
inputs. Register MEMCON configures RH3:RH0 as I/O
or system bus pins.
EXAMPLE 10-8: INITIALIZING PORTH
FIGURE 10-17: RH3:RH0 PINS BLOCK
DIAGRAM IN I/O MODE
FIGURE 10-18: RH7:RH4 PINS BLOCK
DIAGRAM IN I/O MODE
Note: PORTH is available only on PIC18F8X20
devices.
Note 1: On Power-on Reset, PORTH pins
RH7:RH4 default to A/D inputs and read
as ‘0’.
2: On Power-on Reset, PORTH pins
RH3:RH0 default to system bus signals.
CLRF PORTH ; Initialize PORTH by
; clearing output
; data latches
CLRF LATH ; Alternate method
; to clear output
; data latches
MOVLW 0Fh ;
MOVWF ADCON1 ;
MOVLW 0CFh ; Value used to
; initialize data
; direction
MOVWF TRISH ; Set RH3:RH0 as inputs
; RH5:RH4 as outputs
; RH7:RH6 as inputs
Data
Bus
WR LATH
WR TRISH
RD PORTH
Data Latch
TRIS Latch
RD TRISH
Schmitt
Trigger
Input
Buffer
I/O pin
(1)
QD
CK
QD
CK
EN
QD
EN
RD LATH
or
PORTH
Note 1: I/O pins have diode protection to V
DD and VSS.
Data
Bus
WR LATH
WR TRISH
RD PORTH
Data Latch
TRIS Latch
RD TRISH
Schmitt
Trigger
Input
Buffer
I/O pin
(1)
QD
CK
QD
CK
EN
QD
EN
RD LATH
or
PORTH
To A/D Converter
Note 1: I/O pins have diode protection to VDD and VSS.