BCM43907 Preliminary Data Sheet
PMU Sequencing
PMU Sequencing
The PMU sequencer minimizes system power consumption. It enables and disables various system resources
based on a computation of required resources and a table that describes the relationship between resources
and the time required to enable and disable them.
Resource requests can come from several sources: clock requests from cores, the minimum resources defined
in the ResourceMin register, and the resources requested by any active resource-request timers. The PMU
sequencer maps clock requests into a set of resources required to produce the requested clocks.
Each resource is in one of the following four states:
•
•
•
•
enabled
disabled
transition_on
transition_off
The timer contains 0 when the resource is enabled or disabled and a nonzero value when in a transition state.
The timer is loaded with the time_on or time_off value of the resource after the PMU determines that the
resource must be enabled or disabled and decrements on each 32.768 kHz PMU clock. When it reaches 0, the
state changes from transition_off to disabled or transition_on to enabled. If the time_on value is 0, the resource
can transition immediately from disabled to enabled. Similarly, a time_off value of 0 indicates that the resource
can transition immediately from enabled to disabled. The terms enable sequence and disable sequence refer
to either the immediate transition or the timer load-decrement sequence.
During each clock cycle, the PMU sequencer performs the following actions:
•
•
Computes the required resource set based on requests and the resource dependency table.
Decrements all timers whose values are nonzero. If a timer reaches 0, the PMU clears the
ResourcePending bit of the resource and inverts the ResourceState bit.
•
•
•
Compares the request with the current resource status and determines which resources must be enabled
or disabled.
Initiates a disable sequence for each resource that is enabled, is no longer being requested, and has no
powered-up dependents.
Initiates an enable sequence for each resource that is disabled, is being requested, and has all of its
dependencies enabled.
Broadcom®
March 12, 2016 • 43907-DS104-R
Page 22
BROADCOM CONFIDENTIAL
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