2.4.4. Event communication using WFE and SEV instructions

In the Cortex-A15 processor, an external agent can participate in the WFE and SEV event communication using the EVENTI pin. When this pin is asserted, it sends an event message to all the Cortex-A15 processors in the cluster. This is similar to executing an SEV instruction on one processor of the cluster. This enables the external agent to signal to the processor that it has released a semaphore and that the processor can leave the WFE standby power saving mode. The EVENTI input pin must remain HIGH for at least one CLK cycle to be visible by the processors.

The external agent can determine that at least one of the Cortex-A15 processors in the cluster has executed an SEV instruction by checking the EVENTO pin. When any of the Cortex-A15 processor in the cluster executes an SEV instruction, an event is signalled to all the processors in the cluster, and the EVENTO pin is asserted. This pin is asserted HIGH for three CLK cycles when any of the Cortex-A15 processor executes an SEV instruction.

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