C5002
Low Skew Multiple Frequency PCI Clock Generator with EMI Reducing SSCG
Approved Product
Power Up Bi-Directional Pin Timing (all clock outputs)
VDD
Power Supply
CLK (0:9)
Toggle, outputs
Hi-Z (tristate), inputs
Fig.1
Note: a pull-up or logic high programming voltage will select a 66.6 MHz output clock frequency on that specific pin. A
logic low level will select a 33.3 MHz clock frequency in that specific pin.
Output Frequency Selections
The device contains 3 specific output mode type pins. They are:
REF-CLK0/S0
This pin powers up as a 33.3 or 66.6 MHz PCI clock. Via SMBus command byte 1 bit 4 it may be changed to be a
14.318 MHz clock. When it is acting as a PCI clock its frequency may be changed between 33 and 66 Mhz using SMBus
command byte 1 bit 3. The PCI clock may also be initially set at device power up using the bi-directional programming
capability of the pin (device pin number 27)
CLK (1:8)
These are dual frequency PCI clock pins that may be stopped enabled and have their frequency changed at power up
and then on the fly (at any time) via their respective SMBus register control bits.
CLK9/S9
This bit acts in the same manner as the CLK (1:8) bits. Additionally by selection in SMBus byte 3 Bits 5 and 6 it can
output both 16.5 Mhz or 8.25 Mhz on its pin. Like the other clock pins SMBus byte 3 Bit 6 is initially set (via the clocks bi-
directional; pin function) at power up depending on the level of the clocks pin.
NOTE: Clocks REF-CLK0/S0 (pin 27) and CLK1/S1 (pin 26) are powered from VDD1 (pin 28). This data sheet
characterizes the guaranteed performance of these 2 clocks with respect to jitter and skew. Designers that use this
device need to understand that if these 2 clocks are operated at different frequencies (e.g., pin 27 is set to the REF
output mode while pin 26 is enabled at either 33 pr 66 Mhz frequency mode) that the data sheet values of these clocks
will not be guaranteed. It is therefor prudent to disable the CLK1 output when the REF-CLK0/S0 output has been
programmed to output a 14.31818 Mhz clock to realize the devices best performance.
Cypress Semiconductor Corporation
525 Los Coches St.
Document#: 38-07014 Rev. **
5/4/2001
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
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