ST STM32F102 Series Reference Manual page 626

Universal synchronous asynchronous receiver transmitter (USART)
Figure 244. Break detection in LIN mode (11-bit break length - LBDL bit is set)
Case 1: break signal not long enough => break discarded, LBD is not set
Capture Strobe
Break State machine
Read Samples
Case 2: break signal just long enough => break detected, LBD is set
Capture Strobe
Break State machine
Read Samples
Case 3: break signal long enough => break detected, LBD is set
Capture Strobe
Break State machine
Read Samples
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RX line
Idle Bit0 Bit1
0 0
RX line
Idle Bit0 Bit1
0 0
LBD
RX line
Idle Bit0 Bit1
0 0
LBD
“Short” Break F
Bit2 Bit3 Bit4 Bit5 Bit6
0 0 0 0 0
“Short” Break F
Bit2 Bit3 Bit4 Bit5 Bit6
0 0 0 0 0
“Short” Break F
Bit2 Bit3 Bit4 Bit5 Bit6
0 0 0 0 0
Bit7 Bit8 Bit9 Bit10
0 0 0 1
delimiter is immediate
Bit7 Bit8 Bit9 B10
0 0 0 0
Bit7 Bit8 Bit9 Bit10 wait delimiter
0 0 0 0
RM0008
Idle
Idle
Idle