STM8S datasheet(357/467 Pages) STMICROELECTRONICS

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RM0016

Universal asynchronous receiver transmitter (UART)

377

Figure 137. 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 fMASTER 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 fMASTER 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.

STM8S Datasheet(PDF) 357 Page - STMicroelectronics