Datasheet
15
Low Power Features
2.1.2.5
Deep Sleep State
Deep Sleep state is a very low-power state the processor can enter while maintaining
context. Deep Sleep state is entered by asserting the DPSLP# pin while in the Sleep
state. BCLK may be stopped during the Deep Sleep state for additional platform level
power savings. BCLK stop/restart timings on appropriate chipset based platforms with
the CK505 clock chip are as follows:
• Deep Sleep entry: the system clock chip may stop/tristate BCLK within 2 BCLKs of
DPSLP# assertion. It is permissible to leave BCLK running during Deep Sleep.
• Deep Sleep exit: the system clock chip must drive BCLK to differential DC levels
within 2-3 ns of DPSLP# deassertion and start toggling BCLK within 10 BCLK
periods.
To re-enter the Sleep state, the DPSLP# pin must be deasserted. BCLK can be re-
started after DPSLP# deassertion as described above. A period of 15 microseconds (to
allow for PLL stabilization) must occur before the processor can be considered to be in
the Sleep state. Once in the Sleep state, the SLP# pin must be deasserted to re-enter
the Stop-Grant state.
While in Deep Sleep state, the processor is incapable of responding to snoop
transactions or latching interrupt signals. No transitions of signals are allowed on the
FSB while the processor is in Deep Sleep state. Any transition on an input signal before
the processor has returned to Stop-Grant state results in unpredictable behavior.
2.2
Low-Power FSB Features
The processor incorporates FSB low-power enhancements:
• Dynamic On Die Termination disabling
• Low V
CCP
(I/O termination voltage)
The On Die Termination on the processor FSB buffers is disabled when the signals are
driven low, resulting in power savings. The low I/O termination voltage is on a
dedicated voltage plane independent of the core voltage, enabling low I/O switching
power at all times.
2.3
Processor Power Status Indicator (PSI#) Signal
The PSI# signal is asserted when the processor is in a reduced power consumption
state. PSI# can be used to improve light load efficiency of the voltage regulator,
resulting in platform power savings and extended battery life. The algorithm that the
processor uses for determining when to assert PSI# is different from the algorithm
used in previous processors.
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