Though this may not seem like it at the moment, this is a very
important feature (layer re-mapping) in PCB-ST because it can
save hours of work when using a mix of library sources.
When you create a library symbol you place graphic elements on
various data layers. each of these data layers may have been attributed
with a property such as TOP Pads, BOTTOM PADS, etc.. Since users
are free to use and arrange data layers as needed to support a
specific design approach a possible problem can arise when re-using
symbols in a different design wherein the assignment and arrangement
of the various data layers can be quite different. This is where
the Layer-Re-Mapping concept steps in. Rather than simply doing
a straight one-to-one copy of the library symbol to an design
window the software first scans the library layering attributes
and compares them to the design windows current layering attributes.
For example it looks at data layer (1) one in the library and
then sees that it is attributed as a TOPSILK property. It then
scans the design window looking for the first available design
data layer which has the matching attribute property. From this
it develops a partial re-mapping table.
After it completes the first scan it then repeats the scan, but
this time it tries to complete the mapping by doing a one-to-one
assignment of the data layers on the remaining unassigned library
data layers where the target design layer has not as yet been
used in the results of the first pass.
If necessary the software will make one more final pass and take
any remaining unassigned library data layers and assign them what
ever design layers are still free.
In the event that the software may have concerns about the re-mapping
that it has done it will post the re-mapping table for you to
review/re-edit before the transfer is made.
Therefore to avoid seeing the re-mapping tables it is important
that you first make sure that the design window is appropriately
attributed to receive the footprints you will be placing.
One final important note:
This same re-mapping principle is used when copying and pasting
between design windows. This allows you to easily copy and paste
between radically different design configurations with minimal
needed cleanup.