.......................DOC #: SP-AP-0021 (Rev AA) Page 16 of 28
CPU_STP# Assertion
The CPU_STP# signal is an active LOW input used for
synchronous stopping and starting the CPU output clocks
while the rest of the clock generator continues to function.
When the CPU_STP# pin is asserted, all CPU outputs that are
set with the SMBus configuration to be stoppable are stopped
within two to six CPU clock periods after sampled by two rising
edges of the internal CPUC clock. The final states of the
stopped CPU signals are CPUT = HIGH and CPUC = LOW.
CPU_STP# Deassertion
The deassertion of the CPU_STP# signal causes all stopped
CPU outputs to resume normal operation in a synchronous
manner. No short or stretched clock pulses are produced when
the clock resumes. The maximum latency from the
deassertion to active outputs is no more than two CPU clock
cycles.
PCI_STP# Assertion
The PCI_STP# signal is an active LOW input used for
synchronously stopping and starting the PCI outputs while the
rest of the clock generator continues to function. The set-up
time for capturing PCI_STP# going LOW is 10 ns (t
SU
). (See
Figure 6.) The PCIF clocks are affected by this pin if their
corresponding control bit in the SMBus register is set to allow
them to be free running.
.
Figure 4. CPU_STP# Assertion Waveform
CPU_STP#
CPUT
CPUC
CPUT Internal
Tdrive_CPU_STP#,10 ns>200 mV
CPUC Internal
Figure 5. CPU_STP# Deassertion Waveform
Tsu
PCI_STP#
PCI_F
PCI
SRC 100MHz
Figure 6. PCI_STP# Assertion Waveform
