Datasheet

795
SAM9X35 [DATASHEET]
11055E–ATARM–10-Mar-2014
Figure 39-39. Header Transmission
39.7.8.7 Header Reception (Slave Node Configuration)
All the LIN Frames start with a header which is sent by the master node and consists of a Synch Break Field, Synch Field
and Identifier Field.
In Slave node configuration, the frame handling starts with the reception of the header.
The USART uses a break detection threshold of 11 nominal bit times at the actual baud rate. At any time, if 11
consecutive recessive bits are detected on the bus, the USART detects a Break Field. As long as a Break Field has not
been detected, the USART stays idle and the received data are not taken in account.
When a Break Field has been detected, the flag LINBK in the Channel Status register (US_CSR) is set to 1 and the
USART expects the Synch Field character to be 0x55. This field is used to update the actual baud rate in order to stay
synchronized (see Section 39.7.8.8). If the received Synch character is not 0x55, an Inconsistent Synch Field error is
generated (see Section 39.7.8.14).
After receiving the Synch Field, the USART expects to receive the Identifier Field.
When the Identifier Field has been received, the flag LINID in the Channel Status register (US_CSR) is set to 1. At this
moment the field IDCHR in the LIN Identifier register (US_LINIR) is updated with the received character. The Identifier
parity bits can be automatically computed and checked (see Section 39.7.8.9).
The flags LINID and LINBK are reset by writing the bit RSTSTA to 1 in the Control register (US_CR).
TXD
Baud Rate
Clock
Start
Bit
Write
US_LINIR
10101010
TXRDY
Stop
Bit
Start
Bit
ID0 ID1 ID2 ID3 ID4 ID5 ID6 ID7Break Field
13 dominant bits (at 0)
Stop
Bit
Break
Delimiter
1 recessive bit
(at 1)
Synch Byte = 0x55
US_LINIR
ID
LINID
in US_CSR
LINBK
in US_CSR
Write RSTSTA=1
in US_CR