PIC16F882/883/884/886/887
The TRISD register (Register 3-12) 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’.
3.6
PORTD and TRISD Registers
PORTD(1) is a 8-bit wide, bidirectional port. The
corresponding data direction register is TRISD
(Register 3-12). 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 3-5 shows how to initialize PORTD.
EXAMPLE 3-5:
INITIALIZING PORTD
BANKSELPORTD
;
CLRF
BANKSELTRISD
PORTD
;Init PORTD
;
Reading the PORTD register (Register 3-11) 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.
MOVLW
MOVWF
B‘00001100’ ;Set RD<3:2> as inputs
TRISD
;and set RD<7:4,1:0>
;as outputs
Note 1: PORTD is available on PIC16F884/887
only.
REGISTER 3-11: PORTD: PORTD REGISTER
R/W-x
RD7
R/W-x
RD6
R/W-x
RD5
R/W-x
RD4
R/W-x
RD3
R/W-x
RD2
R/W-x
RD1
R/W-x
RD0
bit 7
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-0
RD<7:0>: PORTD General Purpose I/O Pin bit
1= Port pin is > VIH
0= Port pin is < VIL
REGISTER 3-12: TRISD: PORTD TRI-STATE REGISTER
R/W-1
R/W-1
R/W-1
R/W-1
R/W-1
R/W-1
R/W-1
R/W-1
TRISD7
TRISD6
TRISD5
TRISD4
TRISD3
TRISD2
TRISD1
TRISD0
bit 7
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-0
TRISD<7:0>: PORTD Tri-State Control bit
1= PORTD pin configured as an input (tri-stated)
0= PORTD pin configured as an output
© 2007 Microchip Technology Inc.
Preliminary
DS41291D-page 57
MICROCHIP [ MICROCHIP ]
