SCIRXSHF
7 0
SCITXSHF
7 0
RX
TX
CHECKSUM CALCULATOR
Compare
Checksum
Send
Checksum
LIN
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1652
SPNU563A–March 2018
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Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI)/ Local Interconnect Network (LIN)
Module
Figure 29-20. Checksum Compare and Send for Extended Frames
29.3.1.7 Timeout Control
Any LIN node listening to the bus and expecting a response initiated from a master node could flag a no-
response error timeout event. The LIN protocol defines four types of timeout events, which are all handled
by the hardware of the LIN module. The four LIN protocol events are:
• No-response timeout error
• Bus idle detection
• Timeout after wakeup signal
• Timeout after three wakeup signals
29.3.1.7.1 No-Response Error (NRE)
The no-response error will occur when any node expecting a response waits for T
FRAME_MAX
time and the
message frame is not fully completed within the maximum length allowed, T
FRAME_MAX
. After this time a no-
response error (NRE) is flagged in the NRE bit of the SCIFLR register. An interrupt is triggered if enabled.
As specified in the LIN 1.3 standard, the minimum time to transmit a frame is:
T
FRAME_MIN
= T
HEADER_MIN
+ T
DATA_FIELD
+ T
CHECKSUM_FIELD
= 44 + 10N
where N = number of data fields.
And the maximum time frame is given by:
T
FRAME_MAX
= T
FRAME_MIN
* 1.4
= (44 + 10N) * 1.4
The timeout value T
FRAME_MAX
is derived from the N number of data fields value. The N value is either
embedded in the header’s ID field for messages or is part of the description file. In the latter case, the 3-
bit CHAR value in SCIFORMAT register, will indicate the value for N.
NOTE: The length coding of the ID field does not apply to two extended frame identifiers, ID fields of
0x3E (62) and 0x3F (63). In these cases, the ID field can be followed by an arbitrary number
of data byte fields. Also, the LIN 2.0 protocol specification mentions that ID field 0x3F (63)
cannot be used. For these two cases, the NRE will not be handled by the LIN controller
hardware.
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