ST7L34, ST7L35, ST7L38, ST7L39
On-chip peripherals
Doc ID 11928 Rev 7
1.
A LIN Identifier field has been received
2.
An LHE error occurred (other than a timeout error)
3.
A software reset of LSF bit (transition from high to low) occurred during the analysis of
the LIN synch field
4.
If LHE bit is set due to this error during the LIN synchr field (if LASE bit = 1) then the
SCI goes into a blocked state (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 SCI 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 timeout is equal to 1.4 * (34 + 1) = 49 TBIT_MASTER. TBIT_MASTER refers to the
master baud rate.
When checking this timeout, the slave node is desynchronized for the reception of the LIN
break and synch fields. Consequently, a margin must be allowed, taking into account the
worst case: This occurs when the LIN identifier lasts exactly 10 TBIT_MASTER periods. In this
case, the LIN break and synch fields lasts 49 - 10 = 39 TBIT_MASTER periods.
Assuming the slave measures these first 39 bits with a desynchronized clock of 15.5%. This
leads to a maximum allowed header length of: 39 x (1/0.845) TBIT_MASTER + 10TBIT_MASTER
= 56.15 TBIT_SLAVE. A margin is provided so that the time-out occurs when the header
length is greater than 57 TBIT_SLAVE periods. If it is less than or equal to 57 TBIT_SLAVE
periods, then no timeout occurs.
LIN header length
Even if no timeout occurs on the LIN header, it is possible to have access to the effective LIN
header length (THEADER) through the LHL register. This allows monitoring at software level
the TFRAME_MAX condition given by the LIN protocol.
This feature is only available when LHDM bit = 1 or when LASE bit = 1.
Mute mode and errors
In mute mode when LHDM bit = 1, if an LHE error occurs during the analysis of the LIN
synch field or if a LIN header time-out occurs then the LHE bit is set but it does not wake up
from mute mode. In this case, the current header analysis is discarded. If needed, the
software has to reset LSF bit. Then the SCI searches for a new LIN header.
In mute mode, if a framing error occurs on a data (which is not a break), it is discarded and
the FE bit is not set.
When LHDM bit = 1, any LIN header which respects the following conditions causes a wake-
up from mute mode:
●
A valid LIN break field (at least 11 dominant bits followed by a recessive bit)
●
A valid LIN synch field (without deviation error)
●
A LIN identifier field without framing error. Note that a LIN parity error on the LIN
identifier field does not prevent wake-up from mute mode.
●
No LIN header time-out should occur during header reception.