0. background

There are two classic problems:
 - "heavy vs. light symbols", or "where to store the pinout" or "part 
library"
 - how to handle slotting

gschem doesn't really provide a good solution out-of-the-box to the first 
problem, so pretty much every advanced user developed their own solution. 
Gschem solves slotting by sacrificing some of the netlist-backend-driven 
flexibility by hardwiring it in the GUI.

In the cschem model I managed to solve both of these in a generic way so 
that:
 - we do not need to sacrificie flexibility
 - nothing is hardwired in the GUI
 - every single step/stage of the process is optional
 - so you can use plain old heavy symbols, portmapped symbols or devmapped 
symbols or even mix them on a single sheet!

Terminology reminder:
 - symbol is a concrete model object
 - one or more symbols are compiled into an abstract component 
 - terminal is a concrete model object
 - one or more terminals are compiled into an abstract port

So whenever you see "component" or "port", we are talking about the 
abstract model.


1. What's portmap/devmap? (doc)

This explains it all:

http://repo.hu/projects/cschem/user/02_model/display_name.html

We have already tested the heavy symbol approach. The scope of this test 
request is the portmap approach which also makes slotting possible. Devmap 
will be in a later test request.


2. Working example

You find a fully working example in trunk/src/examples/slot2.lht

It features "inhomogeneous slotting" of a 7400. This means the 4 channels 
are done using one box symbol and the power part done by using a different 
box symbol. All these had been generated using boxsym-rnd.

The 5 symbols (all named U1) are merged into a single component (called 
U1) at the end. All terminals in all these symbols are named as per 
function.

One of the symbols, namely the slot=1 one, has a portmap attribute 
specified. This has the mapping of all the digital pins in all the digital 
slots. The mapping is not a plain "terminal_name to pin number" one, but a 
"slot/terminal_name to any-attribute" one. It happens to set pcb/pinnum 
attributes, which makes this mapping useful for the pcb workflow, but it 
could be used to set any attribute on any terminal.

3. Editing the attribute

The easiest way to get to this mapping is to right click over the middle 
of the slot=1 symbol and invoke the symbol attribute dialog. If you 
clicked the propert editor, you find the portmap attribute there too and 
for editing the value, it will take you to the attribute editor.

Test edit: slick on one of the rows of the pinmap, click the edit button 
and modify the rightmost value to 9, then click the compile button on the 
main window: you will see the given terminal changes display name to 9.

If you dislike editing it in the string form, we have assisted edit GUIas 
well: navigate to the portmap attribute in an attribute dialog and click 
the assisted edit. You will get the same mapping info in a table; click on 
a row and you can edit each field separately.


4. Notes on slotting and power slot

The power symbol has pcb pin numbers hardwired in the terminals for 
Vcc and GND. This is because there can be only one power slot of 7400 and 
it always has the same pin numbers. Of course it could be implemented in 
the same manner as the digital pins and then you would have to include 
them in the portmap too.