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AR# 3000

CPLD XC9500 Family - Why do the XC9500 family libraries have pull-up elements?


Keywords: 9500, pullups, pull-ups, XC9500

Urgency: Standard

General Description:
Although the XC9500/XL family devices have pull-ups, they are not user-
controllable. Why are they still included as library elements?



In 3.1i, the pull-up elements have been removed from the CPLD library.

If an internal 3-state mux is drawn in a schematic (using 2 or more
BUFE/BUFT buffers), direct functional simulation of the schematic
will fail to produce a 1 state if all buffers are disabled (actual
chip behavior), unless a pull-up symbol is connected.


Users can retarget an FPGA design containing pullup symbols to
9k without having to remove the pullups; the resulting
implementation will still be accurate.
AR# 3000
Date Created 10/28/1997
Last Updated 10/04/2000
Status Archive
Type General Article