SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
A power domain is a section (that is, a group of modules) of the device with an independent and dedicated power manager (see Figure 3-9). A power domain can be turned on and off without affecting other parts of the device.
To minimize device power consumption, the modules are grouped into power domains. A power domain can be split into logic and memory areas.
The memory area contains two entities:
The logic area in the power domain can also be split between retention flip-flops (RFFs) and nonretention flip-flops (DFFs).
Table 3-18 lists the possible states and substates of the logic area in a power domain.
State | Substate | Description |
---|---|---|
ON | ON-ACTIVE | Logic is fully powered and at least one enclosed clock domain is active. |
ON-INACTIVE | Logic is fully powered and all enclosed clock domains are idled. | |
RETENTION | CSWR (close switch retention) | Logic is fully powered and all enclosed clock domains are idled. |
OFF | Logic power switches are off. All the logic (DFF and RFF) is lost except for the context, which has been saved in the scratchpad memory of an always-on power domain. Vdd can be set to 0 V if all associated power domains are in this state. |
RETENTION state is useful for quickly switching to low-power idle mode (in which the domain clocks are gated and the domain voltage is less than the on-voltage level) without losing the context, and then quickly switching back to ON-ACTIVE state when necessary. In RETENTION state, power consumption is less than in ON power state.
The behavior of the memory array power switch and memory logic power switch can be selected through software settings in the PRCM module or can be hardwired. Once the behavior is selected, the PRCM module hardware automatically handles these elements to ensure correct power transition sequencing between the power domain states.
Software can also initiate power state changes of the memory array when the associated power domain is in ON power state. This allows the memory array to be turned off and on as needed.
The memory area can be configured to any of the power states listed in Table 3-19.
State | Description |
---|---|
ON | The memory array is powered and fully functional. |
RETENTION | The memory array is fully powered, but memory is not accessible. The array can be put into retention through an applicable direct retention control signal. Data in memory are always retained. |
OFF | The memory array is powered down. Data in memory are lost. |