ICS1531 Data Sheet - Preliminary
Chapter 7 Programming
7.3.2 Programming Flow for Modifying Settings for Spread Spectrum
Figure 7-4. ICS1531 Flow for PNLCLK and MCLK PLL Spread-Spectrum Settings
PNLCLK Reg 25:1 = 0
MCLK Reg 2B:1 = 0
Disable Spread
Spectrum Mode
Change
PLL Freq.
Yes
No
?
Set M, N, PFD Gain,
and Output Scaler
PNLCLK Regs 20, 21, 24
MCLK Regs 26, 27, 2A
Change
No
Spread
Spectrum
Mode?
Yes
Set Spread Sepctrum
Counter and Gain
PNLCLK Regs 22, 23, 24
MCLK Regs 28, 29, 2A
PLL Software
Reset
PNLCLK and MCLK
Reg 2D
Wait ~1ms
Yes
PNLCLK Reg 25:1 = 1
MCLK Reg 2B:1 = 1
Enable Spread Spectrum Mode
No
Done
ICS1531 Rev N 12/1/99
December, 1999
Copyright © 1999, Integrated Circuit Systems, Inc.
All rights reserved.
57
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