215
7647H–AVR–03/12
Atmel ATmega16/32/64/M1/C1
17.5.6.2 Re-synchronization in LIN Mode
When waiting for Rx Header, LBT[5..0] = 32 in LINBTR register. The re-synchronization begins
when the BREAK is detected. If the BREAK size is not in the range (11 bits min., 28 bits max. —
13 bits nominal), the BREAK is refused. The re-synchronization is done by adjusting LBT[5..0]
value to the SYNCH field of the received header (0x55). Then the PROTECTED IDENTIFIER is
sampled using the new value of LBT[5..0]. The re-synchronization implemented in the controller
tolerates a clock deviation of ±20% and adjusts the baud rate in a ±2% range.
The new LBT[5..0] value will be used up to the end of the response. Then, the LBT[5..0] will be
reset to 32 for the next header.
The LINBTR register can be used to re-calibrate the clock oscillator.
The re-synchronization is not performed if the LIN node is enabled as a master.
17.5.6.3 Handling LBT[5..0]
LDISR bit of LINBTR register is used to:
• To enable the setting of LBT[5..0] (to manually adjust the baud rate especially in the case of
UART mode). A minimum of 8 is required for LBT[5..0] due to the sampling operation.
• Disable the re-synchronization in LIN Slave Mode for test purposes.
Note that the LENA bit of LINCR register is important for this handling (see Figure 17-8 on page
215).
Figure 17-8. Handling LBT[5..0]
17.5.7 Data Length
Section 17.4.6 “LIN Commands” on page 209 describes how to set or how are automatically set
the LRXDL[3..0] or LTXDL[3..0] fields of LINDLR register before receiving or transmitting a
response.
In the case of Tx Response the LRXDL[3..0] will be used by the hardware to count the number of
bytes already successfully sent.
In the case of Rx Response the LTXDL[3..0] will be used by the hardware to count the number of
bytes already successfully received.
If an error occurs, this information is useful to the programmer to recover the LIN messages.
Write in LINBTR register
LENA ?
(LINCR bit 4)
LDISR
to write
=0
=0
=1
LBT[5..0] forced to 0x20
LDISR forced to 0
Enable re-synch. in LIN mode
LBT[5..0] = LBT[5..0] to write
(LBT[5..0]
min
=8)
LDISR forced to 1
Disable re-synch. in LIN mode
=1
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