A4.6 Power modes

The following figure shows the supported modes for each core domain, and the legal transitions between them.

Figure A4-4 Cortex®-A55 Core Power Domain Mode Transitions
To view this graphic, your browser must support the SVG format. Either install a browser with native support, or install an appropriate plugin such as Adobe SVG Viewer.


The darker (blue) blocks indicate the modes that the core can be initialized into. The dotted line transition from On to Core Dynamic Retention is only allowed if SIMD retention is not implemented or has been disabled.

The power domains can be controlled independently to give different combinations when powered-up and powered-down.

However, only some powered-up and powered-down domain combinations are valid and supported. The following table describes the power modes, and the corresponding supported power domain states for individual cores.

Caution:

States that are not shown in the following tables are unsupported and must not occur.

Table A4-2 Supported core power mode and power domain states

Power mode Power domain Description
PDCPU PDADVSIMD
Debug recovery On On Core on. Advanced SIMD and floating-point block on. Block is active.
On On On Core on. Advanced SIMD and floating-point block on. Block is active.
SIMD dynamic retention On Ret Core on. Advanced SIMD and floating-point block in retention. Block is active.
Core dynamic retention Ret Ret Core retention. Core logic and Advanced SIMD and floating-point block in retention. Logic and RAM retention power only.
Off (emulated) On On Core on. Advanced SIMD and floating-point block on. Block is active.
Off Off Off Core off. Power to the block is gated.

Deviating from the legal power modes can lead to unpredictable results. You must comply with the dynamic power management and powerup and powerdown sequences described in the following sections.

This section contains the following subsections:
Non-ConfidentialPDF file icon PDF version100442_0200_00_en
Copyright © 2016–2018 Arm Limited or its affiliates. All rights reserved.