Using the automatic feature in Protel does work but sometimes does not give you
what you really need. The way I do this is to define a class with the nets you
need to equalize. Then add a rule for the min and max length you need for this
class in Rules/High Speed/Length Constrant. Then define max/min length to some
silly number that will give you an error when you run a DRC check. Switch off
all DRC except for Length Constraint and switch on Online DRC. Now you will get
your netclass producing errors on all its nets and you will see what sort of
average length you will need to work to. Set some more appriopriate value in
your rules and then you can start to manually shorten the long nets or lengthen
the short nets etc. Then you can pick up a net from Browse PCB/Violations and
use Edit/Move/Break to lengthen a section or Edit/Move/End to shorten a section.
One bug is the net you are altering falls to the bottom of the violations list
after the Online DRC has done its thing so you might think you have altered it
to the correct lenght but its still out of range.

BR Clive







Abd ul-Rahman Lomax <[EMAIL PROTECTED]> on 07/01/2004 09:58:11 AM

Please respond to "Protel EDA Forum" <[EMAIL PROTECTED]>

To:   "Protel EDA Forum" <[EMAIL PROTECTED]>
cc:    (bcc: Clive Broome/sdc)

Subject:  Re: [PEDA] Using the "Equalize net lengts" function



At 04:40 AM 1/6/2004, you wrote:
>In the near future I am going to layout a board (in Protel 99SE) with high
>speed digital signals (PC motherboard). The tracks in some of the buses must
>be of same length due to the high speeds and I must use the "Equalize Net
>Lengts" function.
>
>Anybody who has experiences using this function and maybe have some hints
>for optimising for best results ??

Yes, we have used it. For those who don't know, this function adds meanders
to track, i.e., the track wiggles back and forth with a controllable pitch
and side-to-side deviation.

The function is a command in the Tools menu; when run, it "attempts to
match the length of nets identified by the Matched Net Length design rule.
You must set up this design rule prior to running the process. Track
segments will be added to all nets that are shorter than the longest net in
the set of nets." The tool will look for places along the net where there
is room to add the defined meanders, so you might want to think about
providing such space.

You can see your net lengths in the Netlist Status Report, to verify that
the job has been done to your satisfaction. If you need to make some
adjustments, then you'll check your work with that report. It helps if the
nets involved have names such that they will appear next to each other in
the report....











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