On-chip peripherals
ST7L34, ST7L35, ST7L38, ST7L39
Doc ID 11928 Rev 7
When the LIN auto-resynchronization is enabled (LASE bit = 1), the LHE flag detects:
●
That the deviation error on the synch field is outside the LIN specification which allows
up to
± 15.5% of period deviation between the slave and master oscillators.
●
A LIN header reception timeout occurred. If THEADER > THEADER_MAX then the LHE flag
is set. Refer to
Figure 63 (only if LHDM is set to 1).
●
An overflow during the synch field measurement, which leads to an overflow of the
divider registers. If LHE is set due to this error then the SCI goes into a blocked state
(LSF bit is set).
●
That an overrun occurred on Fields other than the Synch Field (as in standard SCI
mode)
Deviation error on the synch field
The deviation error is checked by comparing the current baud rate (relative to the slave
oscillator) with the received LIN synch field (relative to the master oscillator). Two checks are
performed in parallel:
●
The first check is based on a measurement between the first falling edge and the last
falling edge of the synch field. Let us refer to this period deviation as D:
If the LHE flag is set, it means that D > 15.625%
If LHE flag is not set, it means that D < 16.40625%
If 15.625%
≤ D < 16.40625%, then the flag can be either set or reset depending on the
dephasing between the signal on the RDI line and the CPU clock.
●
The second check is based on the measurement of each bit time between both edges
of the synch field. This checks that each of these bit times is large enough compared to
the bit time of the current baud rate.
When LHE is set due to this error then the SCI goes into a blocked state (LSF bit is set).
LIN header time-out error
When the LIN identifier field detection method is used (by configuring LHDM to 1) or when
LIN auto-resynchronization is enabled (LASE bit = 1), the LINSCI 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 signalled
and the LHE bit is set in the SCISR register.
Figure 63.
LIN header reception timeout
The time-out counter is enabled at each break detection. It is stopped in the following
conditions:
THEADER
LIN synch
Identifier
field
break