
2001 Microchip Technology Inc.
Advance Information
DS39541A-page 121
PIC18C601/801
9.8
PORTH, LATH, and TRISH
Registers
PORTH is an 8-bit wide, bi-directional 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 Hi-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
AN18:AN11, while pins RH3:RH0 are multiplexed with
system address bus A19:A16. By default, pins
RH7:RH4 will setup as A/D inputs and pins RH3:RH0
will setup as 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 9-9:
INITIALIZING PORTH
FIGURE 9-16:
RH3:RH0 PINS BLOCK
DIAGRAM IN I/O MODE
FIGURE 9-17:
RH7:RH4 PINS BLOCK
DIAGRAM
Note:
PORTH is available only on PIC18C801
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)
Q
D
CK
Q
D
CK
EN
QD
EN
RD LATH
or
PORTH
Note 1: I/O pins have diode protection to VDD and VSS.
Data
Bus
WR LATH
WR TRISH
RD PORTH
Data Latch
TRIS Latch
RD TRISH
Schmitt
Trigger
Input
Buffer
I/O pin(1)
Q
D
CK
Q
D
CK
EN
QD
EN
RD LATH
or
PORTH
To A/D Converter
Note 1: I/O pins have diode protection to VDD and VSS.