AMD AX1800DMT3C - Athlon XP 1.53 GHz Processor Datasheet page 27

24309E—March 2002
STPCLK#
AMD Athlon™
System Bus
CONNECT
PROCRDY
CLKFWDRST
PCI Bus
Figure 4. AMD Athlon™ System Bus Disconnect Sequence in the Stop Grant State
Chapter 4
Preliminary Information
Figure 4 shows STPCLK# assertion resulting in the processor in
the St op Gra nt st ate and the A MD A thlon syst em bus
disconnected.
Stop Grant
An example of the AMD Athlon system bus disconnect
sequence is as follows:
1. The peripheral controller (Southbridge) asserts STPCLK#
to place the processor in the Stop Grant state.
2. When the processor recognizes STPCLK# asserted, it enters
the Stop Grant state and then issues a Stop Grant special
cycle.
3. When the special cycle is received by the Northbridge, it
deasserts CONNECT, assuming no probes are pending,
initiating a bus disconnect to the processor.
4. The processor responds to the Northbridge by deasserting
PROCRDY.
5. The Northbridge asserts CLKFWDRST to complete the bus
disconnect sequence.
6. After the processor is disconnected from the bus, the
processor enters a low-power state. The Northbridge passes
the Stop Grant special cycle along to the Southbridge.
Power Management
AMD Athlon™ XP Processor Model 6 Data Sheet
Stop Grant
15