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W83194R-39

100MHZ 3-DIMM CLOCK

Winbond 

W83194R-39/-39A

11.0 OPERATION OF DUAL FUCTION PINS

PRELIMINARY

Pins 2, 7, 8, 25, and 26 are dual function pins and are used for selecting different functions in this

device (see Pin description). During power up, these pins are in input mode (see Fig1), therefore,

and are considered input select pins. When Vdd reaches 2.5V, the logic level that is present on these

pins are latched into their appropriate internal registers. Once the correct information are properly

latched, these pins will change into output pins and will be pulled low by default. At the end of the

power up timer (within 3 ms) outputs starts to toggle at the specified frequency.

2.5V

Vdd

#7 PCICLK_F/MODE

#46 REF1/FS2

#25 24/FS1

#26 48/FS0

Output tri-state

Input

Output pull-low

Within 3ms

Output

All other clocks Output tri-state Output pull-low

Each of these pins are a large pull-up resistor ( 250 kΩ @3.3V ) inside. The default state will be logic

1, but the internal pull-up resistor may be too large when long traces or heavy load appear on these

dual function pins. Under these conditions, an external 10 kΩ resistor is recommended to be

connected to Vdd if logic 1 is expected. Otherwise, the direct connection to ground if a logic 0 is

desired. The 10 kΩ resistor should be place before the serious terminating resistor. Note that these

logic will only be latched at initial power on.

If optional EMI reducing capacitor are needed, they should be placed as close to the series

terminating resistor as possible and after the series terminating resistor. These capacitor has typical

values ranging from 4.7pF to 22pF.

- 18 -

Publication Release Date: May 1998

Revision 0.20

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