SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
The wakeup interrupt is used to allow the SCI/LIN module to automatically exit a low-power mode. A SCI/LIN wakeup is triggered when a low level is detected on the receive RX pin, and this clears the POWERDOWN bit.
In LIN mode, any node can terminate sleep mode by sending a wakeup signal, see Figure 13-252. A responder node that detects the bus in sleep mode, and with a wakeup request pending, sends a wakeup signal. The wakeup signal is a dominant value on the LIN bus for TWUSIG; this is at least 5 Tbits for the LIN bus baud rates. The wakeup signal is generated by sending a 0xF0 byte containing 5 dominant Tbits and 5 recessive Tbits.
Assuming a bus with no noise or loading effects, a write of 0xF0 to TD0 loads the transmitter to meet the wakeup signal timing requirement for TWUSIG. Then, setting the GENWU bit transmits the preloaded value in TD0 for a wakeup signal transmission.
The TI TPIC1021 LIN transceiver, upon receiving a wakeup signal, translates it to the microcontroller for wakeup with a dominant level on the RX pin, or a signal to the voltage regulator. While the POWERDOWN bit is set, if the LIN module detects a recessive-to-dominant edge (falling edge) on the RX pin, the LIN module generates a wakeup interrupt if enabled in the SCISETINT register.
According to LIN protocol 2.0, the TI TPIC1021 LIN transceiver detecting a dominant level on the bus longer than 150ms detects it as a wakeup request. The LIN responder is ready to listen to the bus in less than 100ms (TINITIALIZE<100ms) after a dominant-to-recessive edge (end-of-wakeup signal).