PIC16F688-I/STG Microchip Technology, PIC16F688-I/STG Datasheet - Page 35

• Manufacturer Part Number: PIC16F688-I/STG
• Description: IC PIC MCU FLASH 4KX14 14TSSOP
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F688-I/STG

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, POR, WDT
• Number Of I /o: 12
• Program Memory Size: 7KB (4K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 14-TSSOP
• For Use With: XLT14SS-1 - SOCKET TRANSITION 14DIP/14SSOPAC162061 - HEADER INTRFC MPLAB ICD2 20PINAC162056 - HEADER INTERFACE ICD2 16F688
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 data direction register is TRISA. 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 TRISA
bit will always read as ‘1’. Example 4-1 shows how to
initialize PORTA.
Reading the PORTA register reads the status of the
pins, whereas writing to it will write to the PORT latch.
All write operations are read-modify-write operations.
REGISTER 4-1:
REGISTER 4-2:
© 2009 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 bits
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-x
R/W-1
RA5
TRISA4
R/W-0
R/W-1
RA4
U = Unimplemented bit, read as ‘0’
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
‘0’ = Bit is cleared
TRISA3
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’.
EXAMPLE 4-1:
RA3
BANKSEL PORTA
CLRF
MOVLW
MOVWF
BANKSEL ANSEL
CLRF
MOVLW
MOVWF
R-x
R-1
Note:
PORTA
07h
CMCON0
ANSEL
0Ch
TRISA
The ANSEL and CMCON0 registers must
be initialized to configure an analog
channel as a digital input. Pins configured
as analog inputs will read ‘0’.
TRISA2
R/W-0
R/W-1
RA2
INITIALIZING PORTA
x = Bit is unknown
x = Bit is unknown
PIC16F688
;
;Init PORTA
;Set RA<2:0> to
;digital I/O
;
;digital I/O
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
TRISA1
R/W-0
R/W-1
RA1
DS41203E-page 33
TRISA0
R/W-0
R/W-1
RA0
bit 0
bit 0