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AMD Geode™ SC1200/SC1201 Processor Data Book 83
General Configuration Block
32579B
4.5 Clock Generators and PLLs
This section describes the registers for the clocks required
by the GX1 module, Core Logic module, and the Video
Processor, and how these clocks are generated. See Fig-
ure 4-2 for a clock generation diagram.
The clock generators are based on 32.768 KHz and 27.000
MHz crystal oscillators. The 32.768 KHz crystal oscillator is
described in Section 5.5.2 "RTC Clock Generation" on
page 105 (functional description of the RTC).
Figure 4-2. Clock Generation Block Diagram
32.768 KHz
Crystal
External PCI Clock
PLL5
Internal Fast-PCI Clock
PLL6
ACPI Clock (14.318 MHz)
PLL2
Dot Clock
Core Clock
ADL
PLL4
USB Clock (48 MHz)
Divider
SDRAM Clock
32.768 KHz
and I/O Block Clock
Real-Time Clock (RTC)
24.576 MHz
PLL3
AC97_CLK
Divide
by 4
Divide
by 2
(33.3 MHz)
48 MHz
33 MHz
66 MHz
Oscillator
(24.576 MHz)
To PAD
DISABLE
DISABLE
DISABLE
Shutdown
Shutdown
Shutdown
Shutdown
Shutdown
27 MHz
Crystal
Oscillator
CLK27M Ball
(ACPI)
(ACPI)
High-Resolution Timer Clock
Shutdown
CLK
Shutdown
48 MHz
57.273 MHz
25-135 MHz
66.67 MHz
100-333 MHz
Note: V
PLL2
powers PLL2 and PLL5. V
PLL3
powers PLL3, PLL4, and PLL6.