ICS9248-56 Datasheet, PDF (3/11 Pages) Integrated Circuit Systems – Frequency Timing Generator for Pentium II Systems

ICS9248-56
Select Functions
(Functionality determined by TS# and SEL100/66# pin, see below)
Functionality
Tristate
Testmode
CPUCLK
HI - Z
TCLK/2¹
PCI,
PCI_F
HI - Z
TCLK/6¹
REF0
HI - Z
TCLK¹
Notes:
1. TCLK is a test clock driven on the X1 (crystal in pin) input during test mode.
SEL 100/66# TS#
0
0
0
-
0
-
0
1
1
0
1
-
1
-
1
1
Function
Tri-State
(Reserved)
(Reserved)
Active 66.6MHz CPU, 33.3 PCI
Test Mode
(Reserved)
(Reserved)
Active 100MHz CPU, 33.3 PCI
Power Management
Clock Enable Configuration
CPU_STOP# PCI_STOP# PWR_DWN#
X
X
0
0
0
1
0
1
1
1
0
1
1
1
1
CPUCLK
Low
Low
Low
100/66.6MHz
100/66.6MHz
PCICLK PCICLK_F
Low
Low
Low
33.3MHz
33.3 MHz 33.3MHz
Low
33.3MHz
33.3 MHz 33.3MHz
REF
Stopped
Running
Running
Running
Running
Crystal
Off
Running
Running
Running
Running
VCOs
Off
Running
Running
Running
Running
Full clock cycle timing is guaranteed at all times after the system has initially powered up except where noted. During power
up and power down operations using the PD# pin will not cause clocks of a short or longer pulse than that of the running clock.
The first clock pulse coming out of a stopped clock condition may be slightly distorted due to clock network charging circuitry.
Board routing and signal loading may have a large impact on the initial clock distortion also.
ICS9248-56 Power Management Requirements
Latency
SIGNAL
SIGNAL STATE
No. of rising edges of free running
PCICLK
CPU_ STOP#
0 (Disabled)²
1
1 (Enabled)¹
1
PCI_STOP#
0 (Disabled)²
1
1 (Enabled)¹
1
PD#
1 (Normal Operation)³
3ms
0 (Power Down)⁴
2max
Notes.
1. Clock on latency is defined from when the clock enable goes active to when the first valid clock comes out of the device.
2. Clock off latency is defined from when the clock enable goes inactive to when the last clock is driven low out of the device.
3. Power up latency is when PD# goes inactive (high) to when the first valid clocks are output by the device.
4. Power down has controlled clock counts applicable to CPUCLK, PCICLK only.
The REF will be stopped independant of these.
3