Wakeup Request

Any node in a sleeping LIN cluster may request a wakeup.

In the LIN 2.0 specification, the wakeup request is issued by forcing the bus to the dominant state from 250 μs to 5 ms. For this, it is necessary to send the character 0xF0 in order to impose five successive dominant bits. Whatever the baud rate is, this character complies with the specified timings.

• Baud rate min = 1 kbit/s -> t_bit = 1 ms -> 5 t_bit = 5 ms
• Baud rate max = 20 kbit/s -> t_bit = 50 μs -> 5 t_bit = 250 μs

In the LIN 1.3 specification, the wakeup request should be generated with the character 0x80 in order to impose eight successive dominant bits.

The user can choose by the WKUPTYP bit in US_LINMR either to send a LIN 2.0 wakeup request (WKUPTYP = 0) or to send a LIN 1.3 wakeup request (WKUPTYP = 1).

A wakeup request is transmitted by writing a ‘1’ to US_CR.LINWKUP. Once the transfer is completed, US_SR.LINTC flag is asserted. It is cleared by writing a ‘1’ to US_CR.RSTSTA.