AT90S/LS2333 and AT90S/LS4433
44
UART
The AT90S2333/4433 features a full duplex (separate receive and transmit registers) Universal Asynchronous Receiver
and Transmitter (UART). The main features are:
• Baud rate generator generates any baud rate
• High baud rates at low XTAL frequencies
• 8 or 9 bits data
• Noise filtering
• Overrun detection
• Framing Error detection
• False Start Bit detection
• Three separate interrupts on TX Complete, TX Data Register Empty and RX Complete
• Multi-Processor Communication Mode
Data Transmission
A block schematic of the UART transmitter is shown in Figure 40.
Figure 40. UART Transmitter
Data transmission is initiated by writing the data to be transmitted to the UART I/O Data Register, UDR. Data is transferred
from UDR to the Transmit shift register when:
• A new character has been written to UDR after the stop bit from the previous character has been shifted out. The shift
register is loaded immediately.