[f-cpu] Use of VCI for F-CPU core

["Yann Guidon [systeme]" <guidon@messiaen.lip6.fr>]

The VCI interface protocol is defined by the VSI Alliance (vsi.org).
I am investigating whether it can be used in the frame
of F-CPU. Why not Wishbone ? Could be, but VCI
is very simple and does not define a bus or whatever, just the interface.
Exactly what is needed to define a core, without caring for the fine prints
of the reference manuals.  I like VCI to the same point i dislike PCI.

VSIA membership for individuals seems to be free.
It is the way to obtain the VSI documents/specs.
My university is already registered so i already got the VCI spec
for my diplom's work of this year.
Non-individual membership is at least $1000 so (unless
the VSIA board makes an exception) we can't subscribe the
F-CPU team as a group.

http://www.vsi.org/library/specs/deliver011502.pdf
in the last pages, it describes the compliance claim conditions which seem to be fair.

The VCI documents seem to be available free of charge (but after heavy
subscription), a few people in F-CPUland can get them and write
GPL'd source code that can be reused by other people free of charge
(i'm still investigating however).

Note : The goal of VCI is to determine an interface, completely
independently from the interconnexion with other parts. This
point-to-point definition avoids any allocation/grant/sharing stuff,
which is a good reason why i like it. Then, making "bridges" for
other specifications is rather easy (a bridge to Wishbone or AMBA
is left as exercise for those who want to train themselves).
Although the VSI owns a little restrictive copyright on the spec,
nothing keeps one to document the code and describe the protocol.

Hints and discussion welcome

YG
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