the serial USART is used for duplex (two-way) communication between a receiver and transmitter. This is accomplished by equipping the ATmega16 with independent hardware for the transmitter and receiver. The USART is typically used for asychronous communication. That is, there is not a common clock between the transmitter and receiver to keep them synchronized with one another. To maintain synchronization between the transmitter and receiver, framing start and stop bits bits are used at the beginning and of each data byte in a transmission sequence