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ICS950812

0542G—08/21/03

PD# Functionality

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CPU_STOP# - De-assertion (transition from logic "0" to logic "1")

De-assertion of CPU_STOP# Waveforms

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.

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.

PD# - Assertion (transition from logic "1" to logic "0")

Power Down Assertion of Waveforms

0ns

PD#

CPUCLKT 100MHz

CPUCLKC 100MHz

3V66MHz

66MHz_IN

66MHz_OUT

PCICLK 33MHz

USB 48MHz

REF 14.318MHz

25ns

50ns

CPU_STOP#

CPUCLKT(2:0)

*CPUCLKT(2:0)TS

CPUCLKC(2:0)

Tdrive_CPU_STOP# <10ns @ 200mV

*Signal TS is CPUCLKT in Tri-State mode