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PRCM Functional Description
, Sleep and Wake-Up Dependencies, summarizes the possible dependency combinations
between power domains.
3.5.2.2.5 Power Domain Controls
3.5.2.2.5.1 Power Domain Hardware Control
Each power domain in the device is controlled by a dedicated power state controller (PSCON) in the
PRCM module.
When a state transition occurs for a given power domain, the related PSCON automatically manages the
sequence.
The following sequences are for information only. They do not require software control and are
hardware-managed by the PSCON.
•
Active-to-retention transition:
1. The PSCON isolates the power domain outputs.
2. The PSCON saves the flip-flop content.
3. The PSCON opens the power switch.
•
Retention-to-active transition:
1. The PSCON closes the power switch.
2. The PSCON restores the flip-flop content.
3. The PSCON deactivates the isolation of the power domain outputs.
•
Active-to-off transition:
1. The PSCON isolates the power domain outputs.
2. The PSCON opens the power switch.
•
Off-to-active transition:
1. The PSCON closes the power switch.
2. The PSCON deactivates the isolation of the power domain outputs.
Device power domain implementation also depends on hardwired dependencies, both sleep and wake-up
transitions, between power domains. This means a single power domain transitions from one power state
to another depending on the states and transitions of the linked domains.
For details about the dependencies between power domains, see
, Idle and Wake-Up
Management, and
, Basic Programming Model.
3.5.2.2.5.2 Power Domain Software Controls
If all conditions are met to initiate a power domain state transition (all the modules are idle/standby and
the related clocks are shut down), the PRCM module automatically manages the transition according to
the following settings:
•
Dependencies setting: The PRCM.CM_SLEEPDEP_<domain> registers and
PRCM.PM_WKDEP_<domain> registers are used to set/clear programmable dependencies between
power domains.
Not all dependencies are programmable by software; some are hardwired and thus do not allow any
control. For more information about the dependencies between power domains, see
, Idle
and Wake-Up Management, and
, Basic Programming Model.
•
Power state transitions setting: The transitions of each power domain state can be controlled by
software through a set of dedicated status registers (PRCM.PM_PWSTCTRL_<domain_name>) that
allow the configuration of the power state that the domain enters after completing a transition
(PRCM.PM_PWSTCTRL_<domain_name>[1:0] POWERSTATE bit field). These status registers are
used to check the current state of the logic and memories in a power domain and to learn about any
ongoing state transition.
Also, if the power domain offers different settings for logic and memory, the
PRCM.PM_PWSTCTRL_<domain_name> registers allow selection of the state to which the logic and
memory go when the power domain is put in retention. They also allow selection of the state to which
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SWPU177N – December 2009 – Revised November 2010
Power, Reset, and Clock Management
Copyright © 2009–2010, Texas Instruments Incorporated