PIC12F1840-I/P Microchip Technology, PIC12F1840-I/P Datasheet - Page 288

• Manufacturer Part Number: PIC12F1840-I/P
• Description: 7 KB Flash, 256 Bytes RAM, 32 MHz Int. Osc, 6 I/0, Enhanced Mid Range Core 8 PDI
• Manufacturer: Microchip Technology

Specifications of PIC12F1840-I/P

• Processor Series: PIC12F
• Core: PIC
• Program Memory Type: Flash
• Program Memory Size: 7 KB
• Data Ram Size: 256 B
• Interface Type: MI2C, SPI, EUSART
• Number Of Timers: 3
• Operating Supply Voltage: 1.8 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• Package / Case: PDIP-8
• Development Tools By Supplier: MPLAB IDE Software
• Minimum Operating Temperature: - 40 C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC12(L)F1840
26.4
Synchronous serial communications are typically used
in systems with a single master and one or more
slaves. The master device contains the necessary cir-
cuitry 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 inter-
nal clock generation circuitry.
There are two signal lines in Synchronous mode: a bidi-
rectional 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 trans-
missions.
26.4.1
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.
26.4.1.1
Synchronous data transfers use a separate clock line,
which is synchronous with the data. A device config-
ured as a master transmits the clock on the TX/CK line.
The TX/CK pin output driver is automatically enabled
when the EUSART is configured for synchronous
transmit or receive operation. Serial data bits change
on the leading edge to ensure they are valid at the trail-
ing edge of each clock. One clock cycle is generated
for each data bit. Only as many clock cycles are gener-
ated as there are data bits.
26.4.1.2
A clock polarity option is provided for Microwire
compatibility. Clock polarity is selected with the SCKP
bit of the BAUDCON register. Setting the SCKP bit sets
the clock Idle state as high. When the SCKP bit is set,
the data changes on the falling edge of each clock.
DS41441B-page 288
EUSART Synchronous Mode
SYNCHRONOUS MASTER MODE
Master Clock
Clock Polarity
Preliminary
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.
26.4.1.3
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 syn-
chronous 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 pre-
vious character has been completely flushed from the
TSR, the data in the TXREG is immediately transferred
to the TSR. The transmission of the character com-
mences immediately following the transfer of the data
to the TSR from the TXREG.
Each data bit changes on the leading edge of the mas-
ter clock and remains valid until the subsequent leading
clock edge.
26.4.1.4
1.
2.
3.
4.
5.
6.
7.
8.
Note:
Initialize the SPBRGH, SPBRGL register pair
and the BRGH and BRG16 bits to achieve the
desired baud rate (see
Baud Rate Generator
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 bit of the
PIE1 register and the GIE and PEIE bits of the
INTCON register.
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:
 2011 Microchip Technology Inc.
Section 26.3 “EUSART
(BRG)”).