225

PS8315-2

04/08/99

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PI6C103

Precision Clock Synthesizer for Mobile PCs

CPUCLK

(Internal)

CPUCLK

(Internal)

PCICLK_F

(Free-running)

CPU_STOP#

PCI_STOP#

PWR_DWN#

CPUCLK

(External)

CPU_STOP# is an input signal used to turn off the CPU 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 is internally synchronized to the external

PCICLK_Foutput. All other clocks continue to run while the CPU clocks are disabled. The CPU clocks are always stopped in a low

state and started guaranteeing that the high pulse width is a full pulse. CPU clock on latency is 2 or 3 CPU clocks and CPU clock

off latency is 2 or 3 CPU clocks.

CPU_STOP# Timing Diagram

Notes:

1. All timing is referenced to the 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# is an input signal that must be made synchronous to the free running PCI_F.

4. ON/OFF latency shown in the diagram is 2 CPU clocks.

5. All other clocks continue to run undisturbed.

6. PWR_DWN# , PCI_STOP# are shown in a high state.

7. Diagrams shown with respect to 66 MHz. Similar operation as CPU = 100 MHz.

Power Management Timing

Notes:

1. Clock on/off latency is defined as the number of rising edges of free running PCICLKs

between when the clock disable goes low/high to when the first valid clock comes out of

the device.

2. Power-up latency is from when PWR_DWN# goes inactive (HIGH) to when the first valid

clocks are driven from the device.

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