ICS9250-12 Datasheet, PDF (4/12 Pages) Integrated Circuit Systems – Frequency Timing Generator for PENTIUM II/III Systems

ICS9250-12
Power Management Requirements:
Singal
CPU_STOP
PCI_STOP#
PD#
Singal State
0 (disabled)
1 (enabled)
0 (disabled)
1 (enabled)
1 (normal operation)
0 (power down)
Latency
No. of rising edges of
PCICLK
1
1
1
1
3mS
2max.
Note:
1. Clock on/off latency is defined in the number of rising edges of free running PCICLKs between the clock disable goes low/
high to the first valid clock comes out of the device.
2. Power up latency is when PWR_DWN# goes inactive (high to when the first valid clocks are dirven from the device.
CPU_STOP# Timing Diagram
CPU_STOP# is an asynchronous input to the clock synthesizer. It is used to turn off the CPU and 3V66 clocks for low power
operation. CPU_STOP# is asserted asynchronously by the external clock control logic with the rising edge of free running PCI
clock (and hence CPU clock) and must be internally synchronized to the external output. All other clocks will continue to run
while the CPU clocks are disabled. The CPU clocks must always be stopped in a low state and started in such a manner as to
guarantee that the high pulse width is a full pulse. ONLY one rising edge of PCICLK_F is allowed after the clock control logic
switched for both the CPU and 3V66 outputs to become enabled/disabled.
Notes:
1. All timing is referenced to the internal CPUCLK.
2. The internal label means inside the chip and is a reference only. This
in fact may not be the way that the control is designed.
3. CPU_STOP# signal is an input singal that must be made synchronous
to free running PCICLK_F
4. 3V66 clocks also stop/start before
5. PD# and PCI_STOP# are shown in a high state.
6. Diagrams shown with respect to 133MHz. Similar operation when CPU
is 100MHz
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