AN3258

HSI calibration

Doc ID 17825 Rev 1

7/16

Figure 2.

LIN header

Usually, the master node uses a crystal or resonator oscillator to generate the correct baud

rate. The sync field byte is used by the slave node to synchronize with the master clock.

The STM8A/S LINUART peripheral has an automatic resynchronization feature which

makes use of the sync byte field to synchronize with the master baud rate. The automatic

resynchronization feature measures the sync byte field and automatically adjusts the slave

baud rate generator after each LIN sync field reception from the master node (see Figure 3).

Figure 3.

LIN synch field measurement

After each LIN break reception, the time duration between five falling edges on the LIN Rx

19-bit register called SM which is not user accessible. Then, the LIN baud rate divider

(LDIV) is automatically updated at the end of the fifth falling edge.

Note:

STM8A/S slave node (please refer to the clock tree figure in the STM8A and STM8S

reference manuals) and should not be considered as the frequency of the master node.

LIN break

LIN synch

Identifier

Parity bits

field

field

LIN break

Break

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Bit7

Start

bit

Stop

bit

Next

start

bit

LIN synch field

LDIV(n)

LDIV(n+1)

delim.