Intel III Xeon 500 MHz 80525KX5001M User Manual
Product codes
80525KX5001M
Pentium
®
III Xeon™ Processor at 500 and 550 MHz
38
Datasheet
4.2.3
Stop-Grant State — State 3
The Stop-Grant state on the Pentium
III
Xeon processor is entered when the STPCLK# signal is
asserted. The Pentium
III
Xeon processor will issue a Stop-Grant Transaction Cycle. Exit latency
from this mode is 10 BLCK periods after the STPCLK# signal is deasserted.
Since the AGTL+ signal pins receive power from the system bus, these pins should not be driven
(allowing the level to return to V
(allowing the level to return to V
TT
) for minimum power drawn by the termination resistors in this
state. In addition, all other input pins on the system bus should be driven to the inactive state.
BINIT# will not be serviced while the processor is in Stop-Grant state. The event will be latched
and can be serviced by software upon exit from Stop-Grant state.
and can be serviced by software upon exit from Stop-Grant state.
FLUSH# will not be serviced during Stop Grant state.
RESET# will cause the processor to immediately initialize itself; but the processor will stay in Stop
Grant state. A transition back to the Normal state will occur with the deassertion of the STPCLK#
signal.
Grant state. A transition back to the Normal state will occur with the deassertion of the STPCLK#
signal.
A transition to the HALT/Grant Snoop state will occur when the processor detects a snoop phase on
the system bus. A transition to the Sleep state will occur with the assertion of the SLP# signal.
the system bus. A transition to the Sleep state will occur with the assertion of the SLP# signal.
While in the Stop Grant State, all other interrupts will be latched by the Pentium
III
Xeon processor,
and only serviced when the processor returns to the Normal State.
Figure 16. Stop Clock State Machine
2. Auto HALT Power Down State
BCLK running.
Snoops and interrupts allowed.
Snoops and interrupts allowed.
HALT Instruction and
HALT Bus Cycle Generated
HALT Bus Cycle Generated
INIT#, BINIT#, INTR, NMI,
SMI#, RESET#
SMI#, RESET#
1. Normal State
Normal execution.
STPCLK#
Asserted
Asserted
STPCLK#
De-asserted
De-asserted
3. Stop Grant State
BCLK running.
Snoops and interrupts allowed.
Snoops and interrupts allowed.
SLP#
Asserted
Asserted
SLP#
De-asserted
De-asserted
5. Sleep State
BCLK running.
No snoops or interrupts allowed.
No snoops or interrupts allowed.
4. HALT/Grant Snoop State
BCLK running.
Service snoops to caches.
Service snoops to caches.
Snoop Event Occurs
Snoop Event Serviced
Snoop
Event
Occurs
Event
Occurs
Snoop
Event
Serviced
Event
Serviced
STPCL
K# Ass
erted
STPCL
K# De-
asserted