PIC16F688-I/ML Microchip Technology, PIC16F688-I/ML Datasheet - Page 105

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

Specifications of PIC16F688-I/ML

• Program Memory Type: FLASH
• Program Memory Size: 7KB (4K x 14)
• Package / Case: 16-QFN
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, POR, WDT
• Number Of I /o: 12
• 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
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: EUSART/RS- 232/SCI/USB
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 12
• Number Of Timers: 2
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, DM163014, DM164120-4
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8-ch x 10-bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC164324 - MODULE SKT FOR MPLAB 8DFN/16QFNXLT16QFN1 - SOCKET TRANSITION 14DIP TO 16QFNAC162061 - HEADER INTRFC MPLAB ICD2 20PINAC162056 - HEADER INTERFACE ICD2 16F688
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

10.4
Synchronous serial communications are typically used
in systems with a single master and one or more
slaves. The master device contains the necessary
circuitry for baud rate generation and supplies the clock
for all devices in the system. Slave devices can take
advantage of the master clock by eliminating the
internal clock generation circuitry.
There are two signal lines in Synchronous mode: a
bidirectional data line and a clock line. Slaves use the
external clock supplied by the master to shift the serial
data into and out of their respective receive and trans-
mit shift registers. Since the data line is bidirectional,
synchronous operation is half-duplex only. Half-duplex
refers to the fact that master and slave devices can
receive and transmit data but not both simultaneously.
The EUSART can operate as either a master or slave
device.
Start and Stop bits are not used in synchronous
transmissions.
10.4.1
The following bits are used to configure the EUSART
for Synchronous Master operation:
• SYNC = 1
• CSRC = 1
• SREN = 0 (for transmit); SREN = 1 (for receive)
• CREN = 0 (for transmit); CREN = 1 (for receive)
• SPEN = 1
Setting the SYNC bit of the TXSTA register configures
the device for synchronous operation. Setting the CSRC
bit of the TXSTA register configures the device as a
master. Clearing the SREN and CREN bits of the RCSTA
register ensures that the device is in the Transmit mode,
otherwise the device will be configured to receive. Setting
the SPEN bit of the RCSTA register enables the
EUSART. If the RX/DT or TX/CK pins are shared with an
analog peripheral the analog I/O functions must be
disabled by clearing the corresponding ANSEL bits.
10.4.1.1
Synchronous data transfers use a separate clock line,
which is synchronous with the data. A device
configured as a master transmits the clock on the TX/
CK line. The TX/CK pin is automatically configured as
an output when the EUSART is configured for
synchronous transmit operation. Serial data bits
change on the leading edge to ensure they are valid at
the trailing edge of each clock. One clock cycle is
generated for each data bit. Only as many clock cycles
are generated as there are data bits.
10.4.1.2
A clock polarity option is provided for Microwire
compatibility. Clock polarity is selected with the SCKP
bit of the BAUDCTL register. Setting the SCKP bit sets
© 2009 Microchip Technology Inc.
EUSART Synchronous Mode
SYNCHRONOUS MASTER MODE
Master Clock
Clock Polarity
the clock Idle state as high. When the SCKP bit is set,
the data changes on the falling edge of each clock.
Clearing the SCKP bit sets the Idle state as low. When
the SCKP bit is cleared, the data changes on the rising
edge of each clock.
10.4.1.3
Data is transferred out of the device on the RX/DT pin.
The RX/DT and TX/CK pin output drivers are automat-
ically enabled when the EUSART is configured for
synchronous master transmit operation.
A transmission is initiated by writing a character to the
TXREG register. If the TSR still contains all or part of a
previous character, the new character data is held in
the TXREG until the last bit of the previous character
has been transmitted. If this is the first character, or the
previous character has been completely flushed from
the TSR, the data in the TXREG is immediately trans-
ferred to the TSR. The transmission of the character
commences immediately following the transfer of the
data to the TSR from the TXREG.
Each data bit changes on the leading edge of the
master clock and remains valid until the subsequent
leading clock edge.
10.4.1.4
1.
2.
3.
4.
5.
6.
7.
8.
Note:
Initialize the SPBRGH, SPBRG register pair and
the BRGH and BRG16 bits to achieve the
desired baud rate (see Section 10.3 “EUSART
Baud Rate Generator (BRG)”).
Enable the synchronous master serial port by
setting bits SYNC, SPEN and CSRC.
Disable Receive mode by clearing bits SREN
and CREN.
Enable Transmit mode by setting the TXEN bit.
If 9-bit transmission is desired, set the TX9 bit.
If interrupts are desired, set the TXIE, GIE and
PEIE interrupt enable bits.
If 9-bit transmission is selected, the ninth bit
should be loaded in the TX9D bit.
Start transmission by loading data to the
TXREG register.
The TSR register is not mapped in data
memory, so it is not available to the user.
Synchronous Master Transmission
Synchronous Master Transmission
Set-up:
PIC16F688
DS41203E-page 103