ICS9248-143 Datasheet, PDF (3/16 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers for PENTIUM II/IIITM & K6

ICS9248 - 143
General Description
The ICS9248-143 is the single chip clock solution for Notebook designs using thE 440BX, MX, VIAApollo Pro 133, Apollo Pro
Media or MVP4 style chip set. It provides all necessary clock signals for such a system.
Spread spectrum may be enabled through I²C programming. Spread spectrum typically reduces system EMI by 8dB to 10dB.
This simplifies EMI qualification without resorting to board design iterations or costly shielding. The ICS9248-143 employs a
proprietary closed loop design, which tightly controls the percentage of spreading over process and temperature variations.
Serial Configuration Command Bitmap
Byte0: Functionality and Frequency Select Register (default = 0)
Bit
Bit 7
Bit
[2, 6:4]
Bit 3
Bit 1
Bit 0
Description
0 - ±0.25% Spread Spectrum Modulation, Center Spread
1 - 0 to -0.5% Down Spread
Bit [2, 6:4]
CPUCLK
(MHz)
PCICLK
(MHz)
0000
66.67
33.33
0001
100.00
33.33
0010
100.30
33.43
0011
133.33
33.33
0100
105.00
35.00
0101
133.37
33.34
0110
137.00
34.25
0111
75.00
37.50
1000
100.00
33.33
1001
95.00
31.67
1010
97.00
32.33
1011
133.33
33.33
1100
90.00
30.00
1101
96.22
32.07
1110
66.82
33.41
1111
91.50
30.50
0 - Frequency and Spread Spectrum are selected by hardware
select, latched inputs
1 - Frequency is selected by Bit [2, 6:4]; Spread Spectrum is
selected by bit 1
0 - Normal
1 - Spread Spectrum Enabled
0 - Running
1- Tristate all outputs
PWD
1
Note1
0
1
0
Notes:
1, Default at Power-up will be for latched logic inputs to define frequency. Bit [2, 6:4] are default to 0011.
2, PWD = Power-Up Default
3