ICS950813 Datasheet, PDF (18/22 Pages) Integrated Circuit Systems – Frequency Generator with 200MHz Differential CPU Clocks

ICS950813
Advance Information
CPU_STOP# - De-assertion (transition from logic "0" to logic "1")
All CPU outputs that were stopped are to resume normal operation in a glitch free manner. The maximum latency from the
de-assertion to active outputs is to be defined to be between 2 - 6 CPU clock periods (2 clocks are shown). If the I2C
Bit 6 of Byte 1 is programmed to "1" then the stopped CPU outputs will be driven High within 10 nS of CPU_Stop# de-
assertion.
CPU_STOP#
CPUCLKT(2:0)
*CPUCLKT(2:0)TS
CPUCLKC(2:0)
De-assertion of CPU_STOP# Waveforms
Tdrive_CPU_STOP# <10ns @ 200mV
*Signal TS is CPUCLKT in Tri-State mode
PD# - Assertion (transition from logic "1" to logic "0")
When PWRDWN# is sampled low by two consecutive rising edges of CPU clock, then all clock outputs except CPU clocks
must be held low on their next high to low transitions. When the I2C Bit 6 of Byte 0 is programmed to '0' CPU clocks must
be held with the CPU clock pin driven high with a value of 2 x Iref, and CPU# undriven. If Bit 6 of Byte 0 is '1' then both
CPU and CPU# are undriven. Note the example below shows CPU = 133 MHz and Bit 6 of Byte 0 = '0', this diagram and
description is applicable for all valid CPU frequencies 66, 100, 133, 200 MHz.
Due to the state if the internal logic, stopping and holding the REF clock outputs in the LOW state may require more than
one clock cycle to complete.
Power Down Assertion of Waveforms
0ns
PD#
CPUCLKT 100MHz
CPUCLKC 100MHz
3V66MHz
PCICLK 33MHz
USB 48MHz
REF 14.318MHz
25ns
50ns
PD# Functionality
PD#
CPUCLKT CPUCLKC
1
Normal
Normal
0
iref * Mult
Float
3V66
66MHz
Low
PCICLK_F USB/DOT
PCICLK 48MHz
33MHz
48MHz
Low
Low
0708—10/10/02
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