Functional Description
ARM DDI 0388I
Copyright © 2008-2012 ARM. All rights reserved.
2-11
ID073015
Non-Confidential
Entry to Dormant or Shutdown mode must be controlled through an external power controller.
Run mode
Run mode is the normal mode of operation, where all of the functionality of the Cortex-A9
processor is available.
Standby modes
WFI and WFE Standby modes disable most of the clocks in a processor, while keeping its logic
powered up. This reduces the power drawn to the static leakage current, leaving a tiny clock
power overhead requirement to enable the device to wake up.
Entry into WFI Standby mode is performed by executing the
WFI
instruction.
The transition from the WFI Standby mode to the Run mode is caused by:
•
An
IRQ
interrupt, regardless of the value of the CSPR.I bit.
•
An
FIQ
interrupt, regardless of the value of the CSPR.F bit.
•
An asynchronous abort, regardless of the value of the CPSR.A bit.
•
A debug event, if invasive debug is enabled and the debug event is permitted.
•
A CP15 maintenance request broadcast by other processors. This applies to the Cortex-A9
MPCore product only.
Entry into WFE Standby mode is performed by executing the
WFE
instruction.
The transition from the WFE Standby mode to the Run mode is caused by:
•
An
IRQ
interrupt, unless masked by the CPSR.I bit.
•
An
FIQ
interrupt, unless masked by the CPSR.F bit.
•
An asynchronous abort, unless masked by the CPSR.A bit.
•
A debug event, if invasive debug is enabled and the debug event is permitted.
•
The assertion of the
EVENTI
input signal.
•
The execution of an
SEV
instruction on any processor in the multiprocessor system. This
applies to the Cortex-A9 MPCore product only.
•
A CP15 maintenance request broadcast by other processors. This applies to the Cortex-A9
MPCore product only.
The debug request can be generated by an externally generated debug request, using the
EDBGRQ
pin on the Cortex-A9 processor, or from a Debug Halt instruction issued to the
Cortex-A9 processor through the APB debug port.
Standby
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Only wake-up logic
is clocked.
Clock is
disabled, or
powered off
Dormant
Retention
state/voltage
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External wake-up event required to wake up
Shutdown
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External wake-up event required to wake up
Table 2-2 Cortex-A9 processor power modes (continued)
Mode
Cortex-A9
processor
RAM arrays
Cortex-A9
processor
logic
Cortex-A9
data engine
Description