RM0016 Universal asynchronous receiver transmitter (UART)
Doc ID 14587 Rev 8 339/449
LHE is set if one of the following conditions occurs:
● Break Delimiter is too short
● Synch Field is different from 55h
● Framing error in Synch Field or Identifier Field
● A LIN header reception time-out
Note: If a LIN header error occurs, the LSF bit in the UART_CR6 register must be cleared by
software
LIN header time-out error
The UART automatically monitors the THEADER_MAX condition given by the LIN protocol.
If the entire Header (up to and including the STOP bit of the LIN Identifier Field) is not
received within the maximum time limit of 57 bit times then a LIN Header Error is signaled
and the LHE bit is set in the UART_SR register.
Figure 133. LIN header reception time-out
The time-out counter is enabled at each break detection. It is stopped in the following
conditions:
● A LIN Identifier Field has been received
● An LHE error occurred (other than a time-out error).
● A software reset of LSF bit (transition from high to low) occurred during the analysis of
the LIN Synch Field
If LHE bit is set due to this error during the LIN Synch Field (if LASE bit = 1) then the UART
goes into a blocked state (the LSF bit is set).
If LHE bit is set due to this error during Fields other than LIN Synch Field or if LASE bit is
reset then the current received Header is discarded and the UART searches for a new Break
Field.
Note on LIN Header time-out limit
According to the LIN specification, the maximum length of a LIN Header which does not
cause a time-out is equal to:
1.4 * (34 + 1) = 49 TBIT_MASTER.
TBIT_MASTER refers to the master baud rate.
LIN Synch LIN Synch Identifier
Field
Field
Break
T
HEADER
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