PMM Operation
283
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Power Management Module (PMM)
5.3
PMM Operation
It is important to understand some fundamental concepts beforehand.
5.3.1 Power Domain State
Each core power domain can be in one of three states: Active, Idle, or Off.
In the
Active
state, a power domain is fully powered with normal supply voltage.
In the
Idle
state, all clocks to a power domain are turned off (driven low). The supply voltage is still
maintained at the normal level.
In this device, the
Off
state is equivalent to the
Idle
state in terms of power saving. Users can still from a
programmer's model perspective put a power domain into the Off state as if the power domain can be
physically turned off.
NOTE:
This device does not implement power switches to physically isolate the power domain from
its power supply. Putting a power domain into the Off state has no effect to remove leakage
power. Power domains in this device are group of modules surrounded by the isolation cells.
Isolation cells are placed at the outputs of the power domains. When a power domain is put
into Off state, the isolation cells are enabled and force inactive states on the output signals.
PMM and the PSCONs do not know the physical implementation of the power domains. The
logic to control the transition from one power state to another will behave the same as if the
power domains can be physically turned off.
5.3.2 Default Power Domain State
The default state of each power domain, except for PD1, is controlled by TI during production testing via
programmation of individual bits within the reset configuration word in the TI-OTP sector of flash bank 0.
This allows each power domain to default to either the active state or the off state.
5.3.3 Disabling a Power Domain Permanently
TI can also permanently disable any power domain, except for PD1. This is also controlled by
programmation of individual bits within the reset configuration word in the TI-OTP sector of flash bank 0.
5.3.4 Changing Power Domain State
A domain can only change state when commanded by the application. Each domain has an associated 4-
bit key to define the intended power state. When the correct key is programmed, the PMM initiates the
sequence to transition that domain to the commanded state.
5.3.4.1
Turning a Power Domain Off
It is necessary to turn off all clocks going to a power domain before that domain can be powered down.
PMM contains the hardware interlocks to handle this. Each power domain has an associated memory-
mapped register which allows the application to turn off clocks to that power domain.
Steps to power down a domain with logic – PD2, PD3, PD4, PD5, PD6:
1. Write to the PDCLK_DISx register to disable all clocks to the power domain.
2. Write 0xA to the LOGICPDPWRCTRL0 register to power down the domain.
3. Poll for LOGICPDPWRSTATx to become “00”. The power domain is now powered down.