PIC16F882/883/884/886/887
The TRISE register (Register 3-14) controls the PORTE
pin output drivers, even when they are being used as
analog inputs. The user should ensure the bits in the
TRISE register are maintained set when using them as
analog inputs. I/O pins configured as analog input always
read ‘0’.
3.7
PORTE and TRISE Registers
PORTE(1) is a 4-bit wide, bidirectional port. The
corresponding data direction register is TRISE. Setting a
TRISE bit (= 1) will make the corresponding PORTE pin
an input (i.e., put the corresponding output driver in a
High-Impedance mode). Clearing a TRISE bit (= 0) will
make the corresponding PORTE pin an output (i.e.,
enable the output driver and put the contents of the
output latch on the selected pin). The exception is RE3,
which is input only and its TRIS bit will always read as
‘1’. Example 3-6 shows how to initialize PORTE.
Note:
The ANSEL register must be initialized to
configure an analog channel as a digital
input. Pins configured as analog inputs will
read ‘0’.
EXAMPLE 3-6:
INITIALIZING PORTE
Reading the PORTE register (Register 3-13) 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. RE3 reads ‘0’ when MCLRE =
1.
BANKSELPORTE
;
CLRF
PORTE
;Init PORTE
;
;digital I/O
;Bank 1
;
BANKSELANSEL
CLRF
BCF
ANSEL
STATUS,RP1
BANKSELTRISE
MOVLW
MOVWF
B‘00001100’ ;Set RE<3:2> as inputs
TRISE
;and set RE<1:0>
;as outputs
Note 1: RE<2:0> pins are available on
PIC16F884/887 only.
REGISTER 3-13: PORTE: PORTE REGISTER
U-0
—
U-0
—
U-0
—
U-0
—
R-x
R/W-x
RE2
R/W-x
RE1
R/W-x
RE0
RE3
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 7-4
bit 3-0
Unimplemented: Read as ‘0’
RD<3:0>: PORTE General Purpose I/O Pin bit
1= Port pin is > VIH
0= Port pin is < VIL
REGISTER 3-14: TRISE: PORTE TRI-STATE REGISTER
U-0
—
U-0
—
U-0
—
U-0
—
R-1(1)
R/W-1
R/W-1
R/W-1
TRISE3
TRISE2
TRISE1
TRISE0
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 7-4
bit 3-0
Unimplemented: Read as ‘0’
TRISE<3:0>: PORTE Tri-State Control bit
1= PORTE pin configured as an input (tri-stated)
0= PORTE pin configured as an output
Note 1: TRISE<3> always reads ‘1’.
© 2007 Microchip Technology Inc.
Preliminary
DS41291D-page 59
MICROCHIP [ MICROCHIP ]
