ATMEGA 32 CONNECTIONS TO RS232; UDR AND UCSR REGISTERS PRESENTED BY: ADITYA THANVI (130080112002) AESHWARYA JAIN(130080112003) PARINITI DOSHI (130080112017) SANKET RATHOD(130080112044) UNDER THE GUIDENCE OF PROF. HIREN PATEL

BASICS OF SERIAL COMMUNICATION When a microprocessor communicates with the outside world, it provides the data in byte-sized chunks serially.

METHODS OF SERIAL DATA COMMUNICATION The synchronous method transfers a block of data (characters) at a time, while the asynchronous method transfers a single byte at a time. The chips for serial data communication are commonly referred to as UART (universal asynchronous receiver-transmitter) and USART (universal synchronous-asynchronous receiver- transmitter). 

WHAT IS RS232? RS-232 is the acronym for 'Recommended Standard no. 232', the EIA (electronic Industries Association) approved standard for communication via pc serial ports.

RS232 STANDARDS RS232 is the most widely used serial I/O interfacing standard. This standard is used in PCs and numerous types of equipment. Since the standard was set long before the advent of the TTL logic family, its input and output voltage levels are not TTL compatible. In RS232, a 1 is represented by -3 to -25 V, while a 0 bit is +3 to +25 V, making -3 to +3 undefined.

MAX232 To connect any RS232 to a microcontroller system we must use voltage converters such as MAX232 to convert the TTL logic levels to the RS232 voltage levels, and vice versa. MAX232 1C chips are commonly referred to as line drivers.

RS232 PINS The pins and their labels for the RS232 cable, commonly referred to as the DB-25 connector. In labelling, DB-25P refers to the plug connector (male) and DB-25S is for the socket connector (female).

CONNECTIONS TO RS-232

UDR: USART Data Register(16-bit)

The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers share the same I/O address referred to as USART Data Register or UDR. The Transmit Data Buffer Register (TXB) will be the destination for data written to the UDR Register location. Reading the UDR Register location will return the contents of the Receive Data Buffer Register (RXB).

UCSRA: USART Control and Status Register A (8-bit)

UCSRB: USART Control and Status Register B (8-bit)

UCSRC: USART Control and Status Register C (8-bit)

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