Configuration and Low Power Features
While in the Stop-Grant State, SMI#, INIT#, BINIT# and LINT[1:0] will be latched by the
processor, and only serviced when the processor returns to the Normal State. Only one occurrence
of each event will be recognized upon return to the Normal state.
While in Stop-Grant state, the processor will process a system bus snoop.
7.2.4
7.2.5
HALT/Grant Snoop State
The processor will respond to snoop transactions on the system bus while in Stop-Grant state or in
AutoHALT Power Down state. During a snoop transaction, the processor enters the HALT/Grant
Snoop state. The processor will stay in this state until the snoop on the system bus has been
serviced (whether by the processor or another agent on the system bus). After the snoop is serviced,
the processor will return to the Stop-Grant state or AutoHALT Power Down state, as appropriate.
Sleep State
The Sleep state is a low power state in which the processor maintains its context, maintains the
phase-locked loop (PLL), and has stopped all internal clocks. The Sleep state can only be entered
from Stop-Grant state. Once in the Stop-Grant state, the processor will enter the Sleep state upon
the assertion of the SLP# signal. The SLP# pin should only be asserted when the processor is in the
Stop Grant state. SLP# assertions while the processor is not in the Stop-Grant state is out of
specification and may result in unapproved operation.
Snoop events that occur while in Sleep State or during a transition into or out of Sleep state will
cause unpredictable behaviour.
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 system bus while the processor is in Sleep state. Any transition on an
input signal before the processor has returned to Stop-Grant state will result in unpredictable
behaviour.
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 deasserted immediately after RESET# is asserted to ensure the
processor correctly executes the Reset sequence.
While in the Sleep state, the processor is capable of entering an even lower power state, the Deep
Sleep state, by asserting the DPSLP# pin. (See Section 7.2.6.) Once in the Sleep or Deep Sleep
states, the SLP# pin must be de-asserted if another asynchronous system bus event needs to occur.
The SLP# pin has a minimum assertion of one BCLK period.
When the processor is in Sleep state, it will not respond to interrupts or snoop transactions.
7.2.6
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. The DPSLP# pin must be de-asserted to re-
enter the Sleep state. A period of 30 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 can be deasserted to re-enter the Stop-Grant state.
Mobile Intel Pentium 4 Processor-M Datasheet
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