Rainbow Electronics AT90LS4433 - Manual (Page 120)

120
AT90S/LS4433
1042G–AVR–09/02
1. UART Loses Synchronization if RXD Line is Low when UART Receive is
Disabled
The UART will detect a UART start bit and start reception even if the UART is not
enabled. If this occurs, the first byte after reenabling the UART will be corrupted.
Problem Fix/Workaround
Make sure that the RX line is high at start-up and when the UART is disabled. An
external RS-232 level converter keeps the line high during start-up.