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USART Operation: UART Mode
14-9USART Peripheral Interface, UART Mode
14.2.4 USART Receive Enable
The receive enable bit, URXEx, enables or disables data reception on URXDx
as shown in Figure 14−5. Disabling the USART receiver stops the receive
operation following completion of any character currently being received or
immediately if no receive operation is active. The receive-data buffer,
UxRXBUF, contains the character moved from the RX shift register after the
character is received.
Figure 14−5. State Diagram of Receiver Enable
Idle State
(Receiver
Enabled)
Receive
Disable
Receiver
Collects
Character
URXEx = 0
No Valid Start Bit
Not Completed
URXEx = 1
URXEx = 0
URXEx = 1
Valid Start Bit
Handle Interrupt
Conditions
Character
Received
URXEx = 1
URXEx = 0
Note: Re-Enabling the Receiver (Setting URXEx): UART Mode
When the receiver is disabled (URXEx = 0), re-enabling the receiver (URXEx
= 1) is asynchronous to any data stream that may be present on URXDx at
the time. Synchronization can be performed by testing for an idle line
condition before receiving a valid character (see URXWIE).