4.14.4 Wake-up

For the device to wake, it must receive a wake event and all of the power supplies of the device must be at or above operational levels. After wake, the device will be in a state similar to a power-on reset; this includes asserting IRQ_N to indicate that the device is ready for configuration. Unlike a power-on reset, upon wake the STATUS 2 (STS2) register will contain information about the wake event, and, if configured, wake forwarding will automatically send wake signals to additional devices. As after any reset, the device must be reconfigured, as described in the section Initialization.

The host controller can identify that the device was powered up from a wake event, by examining the Wake-up MDI (WKEMDI) and Wake-up WAKE_IN (WKEWI) status bits in the Status 2 (STS2) register indicating the source of the wake event. Once the device has awakened, it will continue to drive the INH pin high causing the ECU to remain awake until the controller initiates a new transition into the SLEEP state. The device may optionally be configured to forward a received wake event to other devices by driving a wake pulse on WAKE_OUT and/or generating a wake signal on the MDI. As the device configuration is reset to its default state upon wake-up, it must be reconfigured, including wake/sleep settings, prior to sleeping again.