Functional Description
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
2-26
ID021414
Non-Confidential
The external agent can determine that at least one of the cores in the cluster has executed an
SEV
instruction by checking the
EVENTO
pin. When
SEV
is executed by any of the cores in the
cluster, an event is signaled to all the cores in the device, and the
EVENTO
pin is asserted. This
pin is asserted HIGH for three
CLKIN
clock cycles when any core in the cluster executes an
SEV
instruction.
2.4.4
Communication to the Power Management Controller
Communication between the Cortex-A53 processor and the system power management
controller can be performed using one or both of the:
•
STANDBYWFI[3:0] and STANDBYWFIL2 signals
.
•
Q-channel
on page 2-27
.
STANDBYWFI[3:0]
and
STANDBYWFIL2
signals
The
STANDBYWFI[n]
signal indicates when an individual core is in idle and low power state.
The power management controller can remove power from an individual core when
STANDBYWFI[n]
is asserted. See
Individual core shutdown mode
on page 2-21
for more
information.
The
STANDBYWFIL2
signal indicates when all individual cores and the L2 memory system
are in idle and low power state. A power management controller can remove power from the
Cortex-A53 processor when
STANDBYWFIL2
is asserted. See
Cluster shutdown mode
without system driven L2 flush
on page 2-22
and
Cluster shutdown mode with system driven L2
flush
on page 2-23
for more information.
Note
The Cortex-A53 processor includes a minimal L2 memory system in configurations without an
L2 cache. Therefore, the power management controller must always wait for assertion of
STANDBYWFIL2
before removing power from the Cortex-A53 processor.
Figure 2-11 on page 2-27
shows how
STANDBYWFI[3:0]
and
STANDBYWFIL2
correspond
to individual cores and the Cortex-A53 processor.