Datasheet

179
7728G–AVR–06/10
ATtiny87/ATtiny167
The LIN protocol says that a message with an identifier from 60 (0x3C) up to 63 (0x3F) uses a
classic checksum (sum over the data bytes only). Software will be responsible for switching
correctly the LIN13 bit to provide/check this expected checksum (the insertion of the ID field in
the computation of the CRC is set - or not - just after entering the Rx or Tx Response
command).
15.5.15 Data Management
15.5.15.1 LIN FIFO Data Buffer
To preserve register allocation, the LIN data buffer is seen as a FIFO (with address pointer
accessible). This FIFO is accessed via the LINDX[2..0] field of LINSEL register through the
LINDAT register.
LINDX[2..0], the data index, is the address pointer to the required data byte. The data byte can
be read or written. The data index is automatically incremented after each LINDAT access if
the LAINC
(active low) bit is cleared. A roll-over is implemented, after data index=7 it is data
index=0. Otherwise, if LAINC
bit is set, the data index needs to be written (updated) before
each LINDAT access.
The first byte of a LIN frame is stored at the data index=0, the second one at the data index=1,
and so on. Nevertheless, LINSEL must be initialized by the user before use.
15.5.15.2 UART Data Register
The LINDAT register is the data register (no buffering - no FIFO). In write access, LINDAT will
be for data out and in read access, LINDAT will be for data in.
In UART mode the LINSEL register is unused.
15.5.16 OCD Support
When a debugger break occurs, the state machine of the LIN/UART controller is stopped
(included frame time-out) and further communication may be corrupted.