PIC16F722AT-ISS Datasheet, PDF (48/286 Pages) Microchip Technology – 28-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC16(L)F722A/723A
6.2 PORTA and the TRISA Registers
PORTA is a 8-bit wide, bidirectional port. The
corresponding data direction register is TRISA
(Register 6-3). Setting a TRISA bit (= 1) will make the
corresponding PORTA pin an input (i.e., disable the
output driver). Clearing a TRISA bit (= 0) will make the
corresponding PORTA pin an output (i.e., enables
output driver and puts the contents of the output latch
on the selected pin). Example 6-1 shows how to
initialize PORTA.
Reading the PORTA register (Register 6-2) 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.
The TRISA register (Register 6-3) controls the PORTA
pin output drivers, even when they are being used as
analog inputs. The user should ensure the bits in the
REGISTER 6-2: PORTA: PORTA REGISTER
R/W-x
RA7
bit 7
R/W-x
RA6
R/W-x
RA5
R/W-x
RA4
TRISA register are maintained set when using them as
analog inputs. I/O pins configured as analog input always
read ‘0’.
Note:
The ANSELA register must be initialized
to configure an analog channel as a digital
input. Pins configured as analog inputs
will read ‘0’.
EXAMPLE 6-1:
BANKSEL PORTA
CLRF PORTA
BANKSEL ANSELA
CLRF ANSELA
BANKSEL TRISA
MOVLW 0Ch
MOVWF TRISA
INITIALIZING PORTA
;
;Init PORTA
;
;digital I/O
;
;Set RA<3:2> as inputs
;and set RA<7:4,1:0>
;as outputs
R/W-x
RA3
R/W-x
RA2
R/W-x
RA1
R/W-x
RA0
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
RA<7:0>: PORTA I/O Pin bit
1 = Port pin is > VIH
0 = Port pin is < VIL
REGISTER 6-3: TRISA: PORTA TRI-STATE REGISTER
R/W-1
TRISA7
bit 7
R/W-1
TRISA6
R/W-1
TRISA5
R/W-1
TRISA4
R/W-1
TRISA3
R/W-1
TRISA2
R/W-1
TRISA1
R/W-1
TRISA0
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
TRISA<7:0>: PORTA Tri-State Control bit
1 = PORTA pin configured as an input (tri-stated)
0 = PORTA pin configured as an output
DS41417B-page 48
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