Low Power Features
termination resistors in this state. In addition, all other input pins on the FSB should
be driven to the inactive state.
RESET# causes the processor to immediately initialize itself, but the processor will
stay in Stop-Grant state. When RESET# is asserted by the system, the STPCLK#,
SLP#, DPSLP#, and DPRSTP# pins must be de-asserted prior to RESET# de-assertion.
When re-entering the Stop-Grant state from the Sleep state, STPCLK# should be de-
asserted after the de-assertion of SLP#.
While in Stop-Grant state, the processor will service snoops and latch interrupts
delivered on the FSB. The processor will latch SMI#, INIT# and LINT [1:0] interrupts
and will service only one of each upon return to the Normal state.
The PBE# signal may be driven when the processor is in Stop-Grant state. PBE# will
be asserted if there is any pending interrupt or Monitor event latched within the
processor. Pending interrupts that are blocked by the EFLAGS.IF bit being clear will
still cause assertion of PBE#. Assertion of PBE# indicates to system logic that the
entire processor should return to the Normal state.
A transition to the Stop-Grant Snoop state occurs when the processor detects a snoop
on the FSB (see Section 2.1.2.3). A transition to the Sleep state (see Section 2.1.2.4)
occurs with the assertion of the SLP# signal.
2.1.2.3
2.1.2.4
Stop-Grant Snoop State
The processor responds to snoop or interrupt transactions on the FSB while in Stop-
Grant state by entering the Stop-Grant Snoop state. The processor will stay in this
state until the snoop on the FSB has been serviced (whether by the processor or
another agent on the FSB) or the interrupt has been latched. The processor returns to
the Stop-Grant state once the snoop has been serviced or the interrupt has been
latched.
Sleep State
The Sleep state is a low-power state in which the processor maintains its context,
maintains the phase-locked loop (PLL), and stops all internal clocks. The Sleep state is
entered through assertion of the SLP# signal while in the Stop-Grant state. The SLP#
pin should only be asserted when the processor is in the Stop-Grant state. SLP#
assertion while the processor is not in the Stop-Grant state is out of specification and
may result in unapproved operation.
In the Sleep state, the processor is incapable of responding to snoop transactions or
latching interrupt signals. No transitions or assertions of signals (with the exception of
SLP#, DPSLP#, or RESET#) are allowed on the FSB while the processor is in Sleep
state. Snoop events that occur while in Sleep state or during a transition into or out of
Sleep state will cause unpredictable behavior. Any transition on an input signal before
the processor has returned to the Stop-Grant state will result in unpredictable
behavior.
If RESET# is driven active while the processor is in the Sleep state, and held active as
specified in the RESET# pin specification, then the processor will reset itself, ignoring
the transition through Stop-Grant state. If RESET# is driven active while the processor
is in the Sleep state, the SLP# and STPCLK# signals should be de-asserted
immediately after RESET# is asserted to ensure the processor correctly executes the
Reset sequence.
14
Datasheet
INTEL [ INTEL ]
