ATtiny167-ESSZ datasheet(168/282 Pages) ATMEL

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168

7728D–AVR–07/09

ATtiny87/ATtiny167

15.4.6.2

Tx Header Function

In accordance with the LIN protocol, only the master task must enable this function. The

header is sent in the appropriate timed slots at the programmed baud rate (c.f. LINBRR & LIN-

BTR registers).

The controller is responsible for:

• The transmission of the BREAK field - 13 dominant bits,

• The transmission of the SYNCH field - character 0x55,

• The transmission of the PROTECTED IDENTIFIER field. It is the full content of the LINIDR

At the end of this transmission, the controller automatically returns to Rx Header / LIN Abort

state (i.e. LCMD[1..0] = 00) after setting the appropriate flags. This function leaves the control-

ler in the same setting as after the Rx Header function. This means that, in LIN 1.3, the

LINDLR register is set with the uncoded length value at the end of the Tx Header function.

During this function, the controller is also responsible for:

• The starting of the Frame_Time_Out,

• The checking of the LIN communication integrity.

15.4.6.3

Rx & TX Response Functions

These functions are initiated by the slave task of a LIN node. They must be used after sending

an header (master task) or after receiving an header (considered as belonging to the slave

task). When the TX Response order is sent, the transmission begins. A Rx Response order

can be sent up to the reception of the last serial bit of the first byte (before the stop-bit).

In LIN 1.3, the header slot configures the LINDLR register. In LIN 2.1, the user must configure

the LINDLR register, either LRXDL[3..0] for Rx Response either LTXDL[3..0] for Tx Response.

When the command starts, the controller checks the LIN13 bit of the LINCR register to apply

the right rule for computing the checksum. Checksum calculation over the DATA bytes and the

PROTECTED IDENTIFIER byte is called enhanced checksum and it is used for communica-

tion with LIN 2.1 slaves. Checksum calculation over the DATA bytes only is called classic

checksum and it is used for communication with LIN 1.3 slaves. Note that identifiers 60 (0x3C)

to 63 (0x3F) shall always use classic checksum.

At the end of this reception or transmission, the controller automatically returns to Rx Header /

LIN Abort state (i.e. LCMD[1..0] = 00) after setting the appropriate flags.

If an LIN error occurs, the reception or the transmission is stopped, the appropriate flags are

set and the LIN bus is left to recessive state.

During these functions, the controller is responsible for:

• The initialization of the checksum operator,

• The transmission or the reception of ‘n’ data with the update of the checksum calculation,

• The transmission or the checking of the CHECKSUM field,

• The checking of the Frame_Time_Out,

• The checking of the LIN communication integrity.

While the controller is sending or receiving a response, BREAK and SYNCH fields can be

detected and the identifier of this new header will be recorded. Of course, specific errors on

the previous response will be maintained with this identifier reception.

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