Dear Matt,

you wrote :

> Leaving CMOS logic inputs floating is bad design practice . The inputs are
> high impedance and wideband and pick up noise that translates in outputs
> toggling state randomly at high speed . This has nothing to do with pcb
> layout and is an electrical design issue.

Absolutely right !

> You shouldn't have to deal with
> this type of problem unless you're also the person who _designed_ the
> schematic and are not just doing the capture and layout. Protel schematic is
> not intended as a digital design tool .

Principally you are right. The primary layouter's job is not to think about the
schematic design,
 --- b u t  ---
electronic engineers "sometimes" are normal human persons and forget  the
"easiest" things. :-)
So i intend the layout designer always to ask the developer, if he finds
something unusual.
Therefore it is necessary to know the basics in the analog and digital design.
I think, if the layout designer doesn't know this, the product will not be able
to approve the EMI tests of an industrial
environment.

Peter Schoepe
( Elektronik-Service Schoepe )

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