57.7.8.17 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 respects 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.

Using the FLEX_US_LINMR.WKUPTYP bit, the user can choose to send either a LIN 2.0 wakeup request (WKUPTYP = 0) or a LIN 1.3 wakeup request (WKUPTYP = 1).

A wakeup request is transmitted by writing the FLEX_US_CR.LINWKUP bit to 1. Once the transfer is completed, the LINTC flag is asserted in the Status register (FLEX_US_CSR). It is cleared by writing a one to the FLEX_US_CR.RSTSTA bit.