Subject: Wire Or/And
From: Kevin Cameron x3251 (Kevin.Cameron@nsc.com)
Date: Tue Aug 13 2002 - 10:01:01 PDT
Just a quick note -
For wired-or and wired-and the drivers of the net can be considered to have different strengths
for 1,0 and X: for wand 0 is strongest, for wor 1 is strongest. For wand you only get a 1 out when
all drivers are 1 or Z, and wor gives a 0 only when all drivers are 0 or Z. The fact that the output
goes to 1 or 0 when all drivers are Z implies there is an additional driver added by the kernel
that does the job of a pull-up or pull-down. If all the drivers of a wor/wand net are handled by
a single D2A it could be assumed that the user will include the pull-up/down in that D2A, however
if the drivers have individual D2As then a D2A needs to be added for the extra kernel driver and it's
driver-type information should indicate it is a kernel pull-up/down - the safe option is to always
include the kernel driver in the driver list.
Kev.
-- National Semiconductor 2900 Semiconductor Drive, Mail Stop A1-520, Santa Clara, CA 95052-8090
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