PRELIMINARY
C9641
133 MHz Clock Generator for ALI 1641 Chipset Systems
Pin Description (Cont.)
PIN No.
Pin Name
IOAPIC
TYPE
OUT
Description
46
14.31818 MHz, 2.5V clock output. This output is used to clock the CPU communication bus
in multi processor systems.
48
IN /
OUT
This is a power on bi-directional pin with an internal pull-up. During power up, this pin is an
input “FS1” for setting the CPU frequency (see table1, page 1) (see app not, page 4). When
the power reaches the rail, this pin becomes a buffered output of the signal applied at Xin
(typically 14.318 MHz).
FS2 /
REF0
44, 43
2
9
10
18, 29, 37
45
47
OUT
2.5V host bus (CPU) clock outputs. See Table 1 Page 1 for frequency programming.
3.3V power supply for reference output clocks and crystal circuitry.
3.3 Volt Power supply for AGP clock.
3.3V power supply for PCI clocks.
3.3 Volt Power supply pins for SDRAM's.
2.5 Volt Power supply pin for CPU (1:0) output buffers.
2.5 Volt Power supply pin for IOAPIC output.
Power supply Ground return pins for the device.
CPU (1:0)
VDDR
VDDA
VDDP
VDDS
VDDC
VDDI
PWR
PWR
PWR
PWR
PWR
PWR
PWR
5, 6, 14, 28,
33, 41, 42,
23
VSS
26
PWR
Power supply pin for the 48 MHz output.
VDD48
Internal pull-ups are typically 250KΩ. They may vary between 200KΩ and 500KΩ.
Power on Bi-Directional Pins
Power Up Condition:
Pins 1, 11, 27, and 48 are Power up bi-directional pins and are used for programming initial power up frequency and
desktop/mobil mode functions in this device (see Pin description, Page 2). During power-up, these pins are in input mode
(see Fig 2, below), therefore, they are considered input select pins internal to the IC. After a settling time, the Selection
data is latched into internal control registers and these pins then become toggling clock outputs.
VDD Rail
Power Supply
Ramp
FS1/REF1
FS0/PCI_F
48_24#MHz/MODE
FS2/REF0
-
Hi-Z Inputs
Toggle Outputs
Select Data is latched into register then pin becomes clock output signal.
Fig. 2
Cypress Semiconductor Corporation
525 Los Coches St.
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Document#: 38-07037 Rev. **
5/02/2001
Page 3 of 18
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