Microchip Technology AC244045 Data Sheet
PIC16F72X/PIC16LF72X
DS41341E-page 80
© 2009 Microchip Technology Inc.
6.5
PORTD and TRISD Registers
PORTD
(1)
is a 8-bit wide, bidirectional port. The
corresponding data direction register is TRISD
(Register 6-13). 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., enable the output driver and
put the contents of the output latch on the selected pin).
Example 6-4 shows how to initialize PORTD.
(Register 6-13). 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., enable the output driver and
put the contents of the output latch on the selected pin).
Example 6-4 shows how to initialize PORTD.
Reading the PORTD register (Register 6-12) reads the
status of the pins, whereas writing to it will write to the
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then written
to the PORT data latch.
status of the pins, whereas writing to it will write to the
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then written
to the PORT data latch.
The TRISD register (Register 6-13) controls the
PORTD pin output drivers, even when they are being
used as analog inputs. The user should ensure the bits
in the TRISD register are maintained set when using
them as analog inputs. I/O pins configured as analog
input always read ‘0’.
PORTD pin output drivers, even when they are being
used as analog inputs. The user should ensure the bits
in the TRISD register are maintained set when using
them as analog inputs. I/O pins configured as analog
input always read ‘0’.
EXAMPLE 6-4:
INITIALIZING PORTD
6.5.1
ANSELD REGISTER
The ANSELD register (Register 6-9) is used to
configure the Input mode of an I/O pin to analog.
Setting the appropriate ANSELD bit high will cause all
digital reads on the pin to be read as ‘0’ and allow
analog functions on the pin to operate correctly.
configure the Input mode of an I/O pin to analog.
Setting the appropriate ANSELD bit high will cause all
digital reads on the pin to be read as ‘0’ and allow
analog functions on the pin to operate correctly.
The state of the ANSELD bits has no affect on digital
output functions. A pin with TRIS clear and ANSEL set
will still operate as a digital output, but the Input mode
will be analog. This can cause unexpected behavior
when executing read-modify-write instructions on the
affected port.
output functions. A pin with TRIS clear and ANSEL set
will still operate as a digital output, but the Input mode
will be analog. This can cause unexpected behavior
when executing read-modify-write instructions on the
affected port.
Note 1: PORTD is available on PIC16F724/LF724
and PIC16F727/LF727 only.
Note:
The ANSELD register must be initialized
to configure an analog channel as a digital
input. Pins configured as analog inputs will
read ‘0’.
to configure an analog channel as a digital
input. Pins configured as analog inputs will
read ‘0’.
BANKSEL PORTD
;
CLRF
PORTD
;Init PORTD
BANKSEL ANSELD
CLRF
ANSELD
;Make PORTD digital
BANKSEL TRISD
;
MOVLW
B‘00001100’
;Set RD<3:2> as inputs
MOVWF
TRISD
;and set RD<7:4,1:0>
;as outputs
REGISTER 6-12:
PORTD: PORTD REGISTER
(1)
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
R/W-x
RD7
RD6
RD5
RD4
RD3
RD2
RD1
RD0
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-0
RD<7:0>: PORTD General Purpose I/O Pin bits
1
1
= Port pin is > V
IH
0
= Port pin is < V
IL
Note 1:
PORTD is not implemented on PIC16F722/723/726/PIC16LF722/723/726 devices, read as ‘0’.