ST STM8S Reference Manual

Universal asynchronous receiver transmitter (UART) RM0016
342/449 Doc ID 14587 Rev 8
Figure 136. UARTDIV read / write operations when LDUM = 1
Deviation error on the synch field
The deviation error is checked by comparing the current baud rate (relative to the slave
oscillator) with the received LIN Synch Field (relative to the master oscillator). Two checks
are performed in parallel.
The first check is based on a measurement between the first falling edge and the last falling
edge of the Synch Field.
● If D1 > 14.84% LHE is set
● If D1< 14.06% LHE is not set
● If 14.06% < D1 < 14.84% LHE can be either set or reset depending on the dephasing
between the signal on UART_RX pin and the f
MASTER
clock
The second check is based on a measurement of time between each falling edge of the
Synch Field
● If D2 > 18.75% LHE is set
● If D2 < 15.62% LHE is not set
● If 15.62% < D2 < 18.75% LHE can be either set or reset depending on dephasing
between the signal on UART_RX pin and the f
MASTER
clock
Note that the UART does not need to check if the next edge occurs slower than expected.
This is covered by the check for deviation error on the full synch byte.
UARTDIV
UARTDIV_NOM
Baud Rate
Read UART2_BRR1
Write UART2_BRR2
Update
RXNE=1
at end of
Synch Field
UARTDIV_MEAS
Write UART2_BRR1
Read UART2_BRR2
Generation
LIN Sync Field
Measurement
LDUM is reset
UARTDIV[3:0]
UARTDIV[11:4]
UARTDIV[15:12]
UARTDIV[3:0]
UARTDIV[11:4]
UARTDIV[15:12]
UARTDIV[3:0]
UARTDIV[11:4]
UARTDIV[15:12]

ST STM8S Specifications

General

Brand	ST
Model	STM8S
Category	Microcontrollers
Language	English