XC2200 Derivatives
System Units (Vol. 1 of 2)
System Control Unit (SCU)
User’s Manual
6-111
V2.1, 2008-08
SCU, V1.13
6.5.5
Power State Controller (PSC)
The Power State Controller (PSC) controls the operation of the EVRs and PVCs and
handles changes in the different control values.
6.5.5.1
General Overview
A power state transition implies in general a change of the core voltages in one or both
core supply domains. Each power state transition consists of several steps to de-couple
the different phases of the State Transition Sequence (STS). A state transition sequence
defines how EVRs and their associated PVCs are controlled and modified when a
voltage change is requested from the system.
Two sets of configuration data are needed to handle all power state transitions:
•
Sequence A is used for ramp-down power transfers
•
Sequence B is used for ramp-up power transfers
Sequence A; it is invoked if a software trigger bit SEQBTRG in register SEQCON is set.
Sequence B; it is invoked if at least one valid wake-up trigger is asserted. If a wake-up
trigger is valid (can be recognized) depends on the currently entered power state. For
sequence B it is required to be pre-configured by the software when a power saving state
is entered where no software can be executed. Sequence B can only started after a
sequence A was performed. If no sequence A was performed the trigger for the
sequence B is treated as pending as long as a sequence A was performed.