ST7LITE39 datasheet(107/167 Pages) STMICROELECTRONICS

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LINSCI

™ SERIAL COMMUNICATION INTERFACE (LIN Mode) (Cont’d)

11.5.9.4 LIN Error Detection

LIN Header Error Flag

The LIN Header Error Flag indicates that an invalid

LIN Header has been detected.

When a LIN Header Error occurs:

– The LHE flag is set

– An interrupt is generated if the RIE bit is set and

the I[1:0] bits are cleared in the CCR register.

If autosynchronization is enabled (LASE bit =1),

this can mean that the LIN Synch Field is corrupt-

ed, and that the SCI is in a blocked state (LSF bit is

set). The only way to recover is to reset the LSF bit

and then to clear the LHE bit.

– The LHE bit is reset by an access to the SCISR

LHE/OVR Error Conditions

When Auto Resynchronization is disabled (LASE

bit =0), the LHE flag detects:

– That the received LIN Synch Field is not equal to

55h.

– That an overrun occurred (as in standard SCI

mode)

– Furthermore, if LHDM is set it also detects that a

LIN Header Reception Timeout occurred (only if

LHDM is set).

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 59. (only if LHDM is set to 1)

– An overflow during the Synch Field Measure-

ment, 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 checking 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 be-

tween the first falling edge and the last falling

edge of the Synch Field. Let’s 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 dephas-

ing 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 cur-

rent 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 59. LIN Header Reception Timeout

The time-out counter is enabled at each break de-

tection. It is stopped in the following conditions:

- A LIN Identifier Field has been received

- An LHE error occurred (other than a timeout er-

ror).

- A software reset of LSF bit (transition from high to

low) occurred during the analysis of the LIN Synch

Field or

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).

LIN Synch

Identifier

Field

Break

THEADER

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