ICS952601 Datasheet, PDF (16/25 Pages) Integrated Circuit Systems – Programmable Timing Control Hub™ for Next Gen P4™ processor

ICS952601
Programmable Timing Control Hub^TM for Next Gen P4^TM Processor
PD#, Power Down
PD# is an asynchronous active low input used to shut off all clocks cleanly prior to clock power.
When PD# is asserted low all clocks will be driven low before turning off the VCO. In PD# de-assertion all clocks will start
without glitches.
PWRDWN#
1
0
CPU CPU # SRC SRC# 3V66 PCIF/PCI USB/DOT
REF Note
Normal Normal Normal Normal 66MHz 33MHz 48MHz 14.318MHz
Iref * 2 or Float Iref * 2 Float Low
Low
Low
Low
Float
or Float
Notes:
1. Refer to tristate control of CPU and SRC clocks in section 7.7 for tristate timing and operation.
2. Refer to Control Registers in section 16 for CPU_Stop, SRC_Stop and PwrDwn SMBus tristate control addresses.
PD# Assertion
PD# should be sampled low by 2 consecutive CPU# rising edges before stopping clocks. All single ended clocks will be
held low on their next high to low transition.
All differential clocks will be held high on the next high to low transition of the complimentary clock. If the control register
determining to drive mode is set to 'tri-state', the differential pair will be stopped in tri-state mode, undriven.
When the drive mode but corresponding to the CPU or SRC clock of interest is set to '0' the true clock will be driven high at
2 x Iref and the complementary clock will be tristated. If the control register is programmed to '1' both clocks will be tristated.
PWRDWN#
CPU, 133MHz
CPU#, 133MHz
SRC, 100MHz
SRC#, 100MHz
3V66, 66MHz
USB, 48MHz
PCI, 33MHz
REF, 14.31818
IDT^TM Progammable Timing Control Hub^TM for Next Gen P4^TM Processor
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701J—01/25/10