PIC16F721-E/SO Microchip Technology, PIC16F721-E/SO Datasheet - Page 47

• Manufacturer Part Number: PIC16F721-E/SO
• Description: 7 KB FLASH, 256 B SRAM, 18 I/O 20 SOIC .300in TUBE
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 16Fr

Specifications of PIC16F721-E/SO

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 17
• Program Memory Size: 7KB (4K x 14)
• Program Memory Type: FLASH
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 12x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.0
There are as many as eighteen 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.
6.1
PORTA is a 8-bit wide, bidirectional port. The
corresponding data direction register is TRISA
(Register
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).
initialize PORTA.
Reading the PORTA register
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
pin output drivers, even when they are being used as
analog inputs. The user should 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’.
EXAMPLE 6-1:
 2010 Microchip Technology Inc.
BANKSEL PORTA
CLRF
BANKSEL ANSELA
CLRF
BANKSEL TRISA
MOVLW
MOVWF
Note:
I/O PORTS
PORTA and the TRISA Registers
6-2). Setting a TRISA bit (= 1) will make the
PORTA
ANSELA
0Ch
TRISA
The ANSELA register must be initialized
to configure an analog channel as a digital
input. Pins configured as analog inputs
will read ‘0’.
(Register
INITIALIZING PORTA
;
;Init PORTA
;
;digital I/O
;
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
Example 6-1
6-2) controls the PORTA
(Register
shows how to
6-1) reads the
6.1.1
Each of the PORTA pins has an individually
configurable internal weak pull-up. Control bits
WPUA<5:0> enable or disable each pull-up (see
Register
turned off when the port pin is configured as an output.
All pull-ups are disabled on a Power-on Reset by the
RABPU bit of the OPTION register.
6.1.2
All of the PORTA pins are individually configurable as
an interrupt-on-change pin. Control bits IOCA<5:0>
enable or disable the interrupt function for each pin
(see
disabled on a Power-on Reset.
For enable interrupt-on-change pins, the present value
is compared with the old value latched on the last read
of PORTA to determine which bits have changed or
mismatched the old value. The ‘mismatch’ outputs of
the last read are OR’d together to set the PORTA
Change Interrupt Flag bit (RABIF) in the INTCON
register. This interrupt can wake the device from Sleep.
The user, in the Interrupt Service Routine, clears the
interrupt by:
1.
2.
A mismatch condition will continue to set flag bit RABIF.
Reading or writing PORTA will end the mismatch
condition and allow flag bit RABIF to be cleared. The
latch holding the last read value is not affected by a
MCLR or Brown-out Reset. After these Resets, the
RABIF flag will continue to be set if a mismatch is
present.
Note:
Any read or write of PORTA. This will end the
mismatch condition.
Clear the flag bit RABIF.
Register
PIC16F/LF720/721
6-5). Each weak pull-up is automatically
WEAK PULL-UPS
INTERRUPT-ON-CHANGE
When a pin change occurs at the same
time as a read operation on PORTA, the
RABIF flag will always be set. If multiple
PORTA pins are configured for the inter-
rupt-on-change, the user may not be able
to identify which pin changed state.
6-6). The interrupt-on-change feature is
DS41430A-page 47