PIC16F631-I/P Microchip Technology Inc., PIC16F631-I/P Datasheet - Page 61

• Manufacturer Part Number: PIC16F631-I/P
• Description: MCU, 8-Bit, 1KW Flash, 64 RAM, 18 I/O, PDIP-20
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F631-I/P

• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 128 Bytes
• Input Output: 18
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 20-pin PDIP
• Programmable Memory: 1.75K Bytes
• Ram Size: 64 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 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.
4.1
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., 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). 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
REGISTER 4-1:
REGISTER 4-2:
© 2007 Microchip Technology Inc.
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7-6
bit 5-0
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7-6
bit 5-0
Note 1:
U-0
U-0
—
—
2:
I/O PORTS
PORTA and the TRISA Registers
TRISA<3> always reads ‘1’.
TRISA<5:4> always reads ‘1’ in XT, HS and LP Oscillator modes.
Unimplemented: Read as ‘0’
RA<5:0>: PORTA I/O Pin bit
1 = Port pin is > V
0 = Port pin is < V
Unimplemented: Read as ‘0’
TRISA<5:0>: PORTA Tri-State Control bit
1 = PORTA pin configured as an input (tri-stated)
0 = PORTA pin configured as an output
U-0
U-0
—
—
PORTA: PORTA REGISTER
TRISA: PORTA TRI-STATE REGISTER
W = Writable bit
‘1’ = Bit is set
W = Writable bit
‘1’ = Bit is set
IH
IL
TRISA5
R/W-1
R/W-x
RA5
PIC16F631/677/685/687/689/690
TRISA4
R/W-x
R/W-1
RA4
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
TRISA3
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 PORTA 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 4-1:
RA3
R-x
R-1
BCF
BCF
CLRF
BSF
CLRF
BSF
BCF
MOVLW 0Ch
MOVWF TRISA
BCF
Note:
STATUS,RP0
STATUS,RP1
PORTA
STATUS,RP1
ANSEL
STATUS,RP0
STATUS,RP1
STATUS,RP0
The ANSEL register must be initialized to
configure an analog channel as a digital
input. Pins configured as analog inputs will
read ‘0’.
TRISA2
R/W-1
R/W-x
RA2
;Bank 0
;
;Init PORTA
;Bank 2
;digital I/O
;Bank 1
;
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
;Bank 0
INITIALIZING PORTA
x = Bit is unknown
x = Bit is unknown
TRISA1
R/W-1
R/W-x
RA1
DS41262D-page 59
TRISA0
R/W-x
R/W-1
RA0
bit 0
bit 0