ICS9248-55 Datasheet, PDF (2/10 Pages) Integrated Circuit Systems – Pentium/Pro/IITM System Clock Chip

ICS9248-55
Pin Descriptions
PIN NUMBER
1, 2
3
PIN NAME
REF0, REF1
GND1
4
X1
5
6, 12, 18
7
8, 10, 11, 13, 14, 16, 17
9, 15
19, 33
20, 32
21
22, 23
24
25, 26, 27
28
29
30
31
37, 41
34, 38
35, 36, 39, 40
42
43
44, 45
46
X2
GND2
PCICLK_F
PCICLK (0:6)
VDD2
VDD
GND
VDD3
48MHz (0:1)
GND3
FS (0:2)
SPREAD#
PD#
CPU_STOP#
PCI_STOP#
VDDL2
GNDL2
CPUCLK (3:0)
N/C
GNDL1
IOAPIC (0:1)
VDDL1
47
SS_SEL
REF2
48
VDD1
TYPE
OUT
PWR
IN
OUT
PWR
OUT
OUT
PWR
PWR
PWR
PWR
OUT
PWR
IN
IN
IN
IN
IN
PWR
PWR
OUT
-
PWR
OUT
PWR
IN
OUT
PWR
DESCRIPTION
14.318MHz clock output
Ground for REF outputs
XTAL_IN 14.318MHz Crystal input, has internal 33pF
load cap and feed back resistor from X2
XTAL_OUT Crystal output, has internal load cap 33pF
Ground for PCI outputs
Free Running PCI output
PCI clock outputs. TTL compatible 3.3V
Power for PCICLK outputs, nominally 3.3V
Isolated power for core, nominally 3.3V
Isolated ground for core
Power for 48MHz outputs, nominally 3.3V
48MHz outputs
Ground for 48MHz outputs
Frequency Select pins
Enables Spread Spectrum feature when LOW
Powers down chip, active low
Halts CPU clocks at logic "0" level when low
Halts PCI Bus at logic "0" level when low
Power for CPU outputs, nominally 2.5V
Ground for CPU outputs.
CPU and Host clock outputs @ 2.5V
Not internally connected
Ground for IOAPIC outputs
IOAPIC outputs (14.318MHz) @ 2.5V
Power for IOAPIC outputs, nominally 2.5V
±.25% Spread Spectrum Selector at power up.
Logic 0 for Downspread
Logic 1 for Centerspread
14.318MHz clock output
Supply for REF (0:2), X1, X2, nominal 3.3V
Select Functions
Functionality
Tristate
Testmode
Spread Spectrum
CPU
HI - Z
TCLK/2¹
Modulated²
PCI,
PCI_F
HI - Z
TCLK/6¹
Modulated²
REF
HI - Z
TCLK¹
14.318MHz
IOAPIC
HI - Z
TCLK¹
14.318MHz
48 MHz
Selection
HI - Z
TCLK/2¹
48.0MHz
FS2 FS1 FS0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
CPU MHz
133
83.3
75
66.6
124
133
112
100
PCI MHz
33.25
41.65
37.5
33.3
41.33
44.3
37.3
33.3
2