Event communication with an external agent using WFE/SEV
A peripheral connected on the coherency port or any other external agent can participate in the WFE/SEV event communication of the Cortex®‑A9 MPCore processor by using the EVENTI pin.
When this pin is asserted, it sends an event message to all the Cortex‑A9 processors in the cluster. This is similar to executing a SEV instruction on one processor of the cluster. This enables the external agent to signal to the processors that it has released a semaphore and that the processors can leave the power-saving mode. The EVENTI input pin must remain high at least one CPUCLK clock cycle to be visible by the processors.
The external agent can see that at least one of the Cortex‑A9 processors in the cluster has executed an SEV instruction by checking the EVENTO pin. This pin is set high for one CLK clock cycle when any of the Cortex‑A9 processors in the cluster executes an SEV instruction.