4.14.4.2 Using a Pin for Wake Forwarding

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This section applies to devices of revision D0 and later.

When selected, wake forwarding will generate a valid wake pulse upon wake from SLEEP on either the WAKE_OUT pin or the WAKE_IN/WAKE_IO pin.

Wake forwarding is enabled by setting the Wake Forward Enable (WKOFWDEN) bit of the Sleep Control 1 (SLPCTL1) register prior to entering the SLEEP state. When enabling this feature, ensure that the desired output pin is selected as described below.

WAKE_OUT pin

WAKE_OUT is configured as a push-pull output. It cannot be connected to another output. This behavior is configured by default, or can be reconfigured by writing a ‘0’ into the WAKE_IO Enable (WIOEN) bit of the Sleep Control 1 (SLPCTL1) register.

Tip: The WAKE_OUT pin is shared with RXCLK on the LAN8670 and can be used only if the device is configured for RMII operation.
Important: The WAKE_OUT pin operates from the VDDP power domain and therefore will only be asserted once the external VDDP supply has been powered.

WAKE_IN/WAKEIO pin

If the WAKE_OUT pin is not available or there is a need for multiple devices are to be connected as wake sources, the WAKE_IN/WAKE_IO pin can be configured to provide wake forwarding and it becomes an open-drain input/output. In this mode, the pin is still available as a wake input as described in the section External Pin Wake-up. When WAKE_IN/WAKE_IO is selected for wake forwarding, the WAKE_OUT pin will be unused and is connected internally to ground.

To select WAKE_IN/WAKE_IO as the output for wake forwarding write a ‘1’ into the WAKE_IO Enable (WIOEN) bit of the Sleep Control 1 (SLPCTL1) register. The polarity of the both the detected and generated wake pulse is determined by the WAKE_IN Polarity (WIPOL) bit in the SLPCTL1 register.