PIC16F684-ISL

Manufacturer Part NumberPIC16F684-ISL
ManufacturerMicrochip Technology Inc.
PIC16F684-ISL datasheets
 

Specifications of PIC16F684-ISL

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4.0
I/O PORTS
There are as many as twelve general purpose I/O pins
available. Depending on which peripherals are
enabled, some or all of the pins may not be available as
general purpose I/O. In general, when a peripheral is
enabled, the associated pin may not be used as a
general purpose I/O pin.
Note:
Additional information on I/O ports may be
®
found in the “PICmicro
Mid-Range MCU
Family Reference Manual” (DS33023).
4.1
PORTA and the TRISA Registers
PORTA is a 6-bit wide, bidirectional port. The
corresponding data direction register is TRISA
(Register 4-2). Setting a TRISA bit (= 1) will make the
corresponding PORTA pin an input (i.e., put the
corresponding output driver in a High-impedance
mode). Clearing a TRISA bit (= 0) will make the
corresponding PORTA pin an output (i.e., put the
contents of the output latch on the selected pin). The
exception is RA3, which is input only and its TRIS bit
will always read as ‘1’. Example 4-1 shows how to
initialize PORTA.
Reading the PORTA register (Register 4-1) 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. RA3 reads ‘0’ when
MCLRE = 1.
The TRISA register controls the direction of the
PORTA pins, even when they are being used as analog
inputs. The user must ensure the bits in the TRISA
register are maintained set when using them as analog
inputs. I/O pins configured as analog input always read
‘0’.
Note:
The ANSEL (91h) and CMCON0 (19h)
registers must be initialized to configure
an analog channel as a digital input. Pins
configured as analog inputs will read ‘0’.
REGISTER 4-1:
PORTA – PORTA REGISTER (ADDRESS: 05h)
U-0
bit 7
bit 7-6:
Unimplemented: Read as ‘0’
bit 5-0:
RA<5:0>: PORTA I/O Pin bit
1 = Port pin is > V
0 = Port pin is < V
Legend:
R = Readable bit
-n = Value at POR
 2004 Microchip Technology Inc.
EXAMPLE 4-1:
BCF
STATUS,RP0
CLRF
PORTA
MOVLW
07h
MOVWF
CMCON0
BSF
STATUS,RP0
CLRF
ANSEL
MOVLW
0Ch
MOVWF
TRISA
BCF
STATUS,RP0
4.2
Additional Pin Functions
Every PORTA pin on the PIC16F684 has an interrupt-
on-change option and a weak pull-up option. RA0 has
an Ultra Low-Power Wake-up option. The next three
sections describe these functions.
4.2.1
WEAK PULL-UPS
Each of the PORTA pins, except RA3, has an individu-
ally configurable internal weak pull-up. Control bits
WPUAx enable or disable each pull-up. Refer to
Register 4-3. Each weak pull-up is automatically turned
off when the port pin is configured as an output. The
pull-ups are disabled on a Power-on Reset by the
RAPU bit (OPTION_REG<7>). A weak pull-up is auto-
matically enabled for RA3 when configured as MCLR
and disabled when RA3 is an I/O. There is no software
control of the MCLR pull-up.
U-0
R/W-x
R/W-x
R/W-x
RA5
RA4
RA3
IH
IL
W = Writable bit
U = Unimplemented bit, read as ‘0’
‘1’ = Bit is set
‘0’ = Bit is cleared
Preliminary
PIC16F684
INITIALIZING PORTA
;Bank 0
;Init PORTA
;Set RA<2:0> to
;digital I/O
;Bank 1
;digital I/O
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
;Bank 0
R/W-x
R/W-0
R/W-0
RA2
RA1
RA0
bit 0
x = Bit is unknown
DS41202C-page 31