Both, Parallel and Serial modes of communication have certain advantages and disadvantages over one another. The serial communication is a preferred option due to its ability of long distance communication with error detection capability. The microcontrollers consist of an inbuilt hardware unit known as USART (Universal Synchronous Asynchronous Reception and Transmission) to facilitate serial transfer of data. For more details, refer to USART in AVR section.
Before starting USART, some general terms related to communication need to be understood. These terms are explained below.


Bit 7
|
Bit 6
|
Bit 5
|
Bit 4
|
Bit 3
|
Bit 2
|
Bit 1
|
Bit 0
|
CSRC
|
TX9
|
TXEN
|
SYNC
|
SENDB
|
BRGH
|
TRMT
|
TX9D
|
Bit 7
|
Bit 6
|
Bit 5
|
Bit 4
|
Bit 3
|
Bit 2
|
Bit 1
|
Bit 0
|
SPEN
|
RX9
|
SREN
|
CREN
|
ADDEN
|
FERR
|
OERR
|
RX9D
|
Fig. 5: Bit configuration of RCSTA /Receive Status and Control Register in EUSART of PIC Microcontroller
Bit 7
|
Bit 6
|
Bit 5
|
Bit 4
|
Bit 3
|
Bit 2
|
Bit 1
|
Bit 0
|
SPPIF
|
ADIF
|
RCIF
|
TXIF
|
SSPIF
|
CCP1IF
|
TMR2IF
|
TMR1IF
|
Fig. 6: Bit Configuration of PIR1 /Peripheral Interrupt Request Register of PIC’s EUSART
Bit 7
|
Bit 6
|
Bit 5
|
Bit 4
|
Bit 3
|
Bit 2
|
Bit 1
|
Bit 0
|
SPPIE
|
ADIE
|
RCIE
|
TXIE
|
SSPIE
|
CCP1IE
|
TMR2IE
|
TMR1IE
|
Fig. 7: Bit configuration of PIE1/ Peripheral Interrupt Enable Register 1of EUSART in PIC Microcontroller
Bit 7
|
Bit 6
|
Bit 5
|
Bit 4
|
Bit 3
|
Bit 2
|
Bit 1
|
Bit 0
|
ABDOVF
|
RCIDL
|
RXDTP
|
TXCKP
|
BRG16
|
—
|
WUE
|
ABDEN
|
Configuration Bits
|
BRG/EUSART Mode
|
Baud Rate Formula
|
||
SYNC
|
BRG16
|
BRGH
|
||
0
|
0
|
0
|
8-bit/Asynchronous
|
Fosc / [64 (n + 1)]
|
0
|
0
|
1
|
8-bit/Asynchronous
|
Fosc / [16 (n + 1)]
|
0
|
1
|
0
|
16-bit/Asynchronous
|
|
0
|
1
|
1
|
16-bit/Asynchronous
|
Fosc / [4 (n + 1)]
|
1
|
0
|
x
|
8-bit/Synchronous
|
|
1
|
1
|
x
|
16-bit/Synchronous
|

Project Source Code
###
// Program to depict the configuration of EUSART in PIC18F4550 // This code receives and then transmits the same data back to the PC .. // ..through PC's Serial Port // Configuration bits /* _CPUDIV_OSC1_PLL2_1L, // Divide clock by 2 _FOSC_HS_1H, // Select High Speed (HS) oscillator _WDT_OFF_2H, // Watchdog Timer off MCLRE_ON_3H // Master Clear on */ void tx_data(unsigned char); unsigned char rx_data(void); unsigned char serial_data; unsigned int i=0; #define FREQ 12000000 // Frequency = 12MHz #define baud 9600 #define spbrg_value (((FREQ/64)/baud)-1) // Refer to the formula for Baud rate calculation in Description tab void main() { SPBRG=spbrg_value; // Fill the SPBRG register to set the Baud Rate RCSTA.SPEN=1; // To activate Serial port (TX and RX pins) TXSTA.TXEN=1; // To enable transmission RCSTA.CREN=1; // To enable continuous reception while(1) { serial_data=rx_data(); // Receive data from PC tx_data(serial_data); // Transmit the same data back to PC } } void tx_data(unsigned char data1) { TXREG=data1; // Store data in Transmit register while(PIR1.TXIF==0); // Wait until TXIF gets low } unsigned char rx_data(void) { while(PIR1.RCIF==0); // Wait until RCIF gets low return RCREG; // Retrieve data from reception register }
###
Circuit Diagrams
Project Components
Project Video
Filed Under: PIC Microcontroller
Filed Under: PIC Microcontroller
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