W83L197R-16 Datasheet, PDF (8/11 Pages) Winbond – 2-CHIP 100MHZ CLOCK FOR BX NOTEBOOK

W83L197R-16
PRELIMINARY
9.0 OPERATION OF DUAL FUCTION PINS
Pin16 and pin26 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
#16 48/SPREAD*
#26 REF2X/FS0*
Output
tri-state
All other clocks
Input
Output
tri-state
Output
pull-low
Within 3ms
Output
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. The same 10 kΩ 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.
Publication Release Date: Mar. 1999
-8-
Revision 0.10