CY28409 Cypress Semiconductor, CY28409 Datasheet - Page 11

• Manufacturer Part Number: CY28409
• Description: Clock Synthesizer with Differential SRC and CPU Outputs
• Manufacturer: Cypress Semiconductor

Document #: 38-07445 Rev. *B
PCI_STP# Assertion
The PCI_STP# signal is an active LOW input used for
synchronous 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
Figure 7.) The PCIF clocks will not be affected by this pin if
their corresponding control bit in the SMBus register is set to
allow them to be free-running.
PCI_STP# Deassertion
The deassertion of the PCI_STP# signal will cause all PCI and
stoppable PCIF clocks to resume running in a synchronous
manner within two PCI clock periods after PCI_STP# transi-
tions to a high level.
Note:
2.
The PCI STOP function is controlled by two inputs. One is the device PCI_STP# pin number 34 and the other is SMBus byte 0 bit 3. These two inputs are logically
ANDed. If either the external pin or the internal SMBus register bit is set low then the stoppable PCI clocks will be stopped in a logic low state. Reading SMBus
Byte 0 Bit 3 will return a 0 value if either of these control bits are set LOW thereby indicating the device’s stoppable PCI clocks are not running.
SRC 100MHz
SRC 100MHz
PCI_STP#
PCI_STP#
[2]
PCI_F
PCI_F
PCI
PCI
Tsu
Figure 8. PCI_STP# Deassertion Waveform
Tsu
Figure 7. PCI_STP# Assertion Waveform
Tdrive_SRC
SU
). (See
CY28409
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