PIC16F636-I/P Microchip Technology Inc., PIC16F636-I/P Datasheet - Page 41

• Manufacturer Part Number: PIC16F636-I/P
• Description: 14 PIN, 3.5 KB FLASH, 128 RAM, 12 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F636-I/P

• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 12
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 14-pin PDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 128 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

4.0
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.
4.1
PORTA is a 6-bit wide, bidirectional port. The
corresponding
(Register 4-4). 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 4-3) 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 inputs always
read ‘0’.
EXAMPLE 4-1:
© 2005 Microchip Technology Inc.
BCF
BCF
CLRF
MOVLW
MOVWF
BSF
BCF
MOVLW
MOVWF
BCF
BCF
Note:
I/O PORTS
PORTA and the TRISA Registers
STATUS,RP0
STATUS,RP1
PORTA
07h
CMCON0
STATUS,RP0
STATUS,RP1
0Ch
TRISA
STATUS,RP0
STATUS,RP1
The CMCON0 (19h) register must be
initialized to configure an analog channel
as a digital input. Pins configured as
analog inputs will read ‘0’.
data
INITIALIZING PORTA
direction
;Bank 0
;
;Init PORTA
;Set RA<2:0> to
;digital I/O
;Bank 1
;
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
;Bank 0
;
register
is
TRISA
PIC12F635/PIC16F636/639
Preliminary
4.2
Every PORTA pin on the PIC12F635/PIC16F636/639
has an interrupt-on-change option and a weak pull-up/
pull-down option. RA0 has an Ultra Low-Power Wake-
up option. The next three sections describe these
functions.
4.2.1
Each of the PORTA pins, except RA3, has an internal
weak pull-up and pull-down. The WDA bits select either
a pull-up or pull-down for an individual port bit.
Individual control bits can turn on the pull-up or pull-
down. These pull-ups/pull-downs are automatically
turned off when the port pin is configured as an output,
as an alternate function or on a Power-on Reset,
setting the RAPU bit (OPTION_REG<7>). A weak pull-
up on RA3 is enabled when configured as MCLR in the
Configuration Word register and disabled when high
voltage is detected, to reduce current consumption
through RA3, while in Programming mode.
Note:
Additional Pin Functions
TRISA = TRISIO
WEAK PULL-UP/PULL-DOWN
PORTA = GPIO
DS41232B-page 39