ARM Cortex-A8 MPU Subsystem
NOTE:
L1 and L2 array memories have separate control signals into the in MPU Subsystem, thus
directly controlled by PRCM For details on the physical power domains and the voltage
domains, see
, Power, Reset, and Clock Management (PRCM).
3.1.6.2
Power States
Each power domain can be driven by the PRCM in 3 different states, depending on the functional mode
required by the user.
For each power domain the PRCM manages all transitions by controlling domain clocks, domain resets,
domain logic power switches and memory power switches.
Table 3-5. MPU Power States
Power State
Logic Power
Memory Power
Clocks
Active
On
On or Off
On (at least one clock)
Inactive
On
On or Off
Off
Off
Off
Off
Off (all clocks)
3.1.6.3
Power Modes
The major part of the MPU subsystem belongs to the MPU power domain. The modules inside this power
domain can be off at a time when the ARM processor is in an OFF or standby mode. IDLE/WAKEUP
control is managed by the clock generator block but initiated by the PRCM module.
The MPU Standby status can be checked with PRCM.CM_IDLEST_MPU[0] ST_MPU bit. For the MPU to
be on, the core (referred here as the device core) power must be on. Device power management does not
allow INTC to go to OFF state when MPU domain is on (active or one of retention modes).
The NEON core has independent power off mode when not in use. Enabling and disabling of NEON can
be controlled by software.
CAUTION
The MPU L1 cache memory does not support retention mode, and its array
switch is controlled together with the MPU logic. For compliance, the L1
retention control signals exist at the PRCM boundary, but are not used. The
ARM L2 can be put into retention independently of the other domains.
outlines the supported operational power modes. All other combinations are illegal. The ARM
L2, NEON, and ETM/Debug can be powered up/down independently. The APB/ATB ETM/Debug column
refers to all three features: ARM emulation, trace, and debug.
The MPU subsystem must be in a power mode where the MPU power domain, NEON power domain,
debug power domain, and INTC power domain are in standby, or off state.
173
SPRUH73H – October 2011 – Revised April 2013
ARM MPU Subsystem
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