[Ftk_hardware] VME access for the AUX card

Paola Giannetti paola.giannetti at pi.infn.it
Sun Dec 26 04:12:27 CST 2010

Mel Shochet wrote:
> Dear Paola,
Dear Mel,
I agree that VME and "not serialized communication lines" between the 
AUX board and the AMB is again something we have to discuss.

Since the P3 connector is used for serialized links (it is specialized 
for that), I was thinking to use VME user defined pins for 
board-to-board TTL connections.  Can we use J2 pins?  For  example these 
could be used for Hold and Freeze signals.

Regarding VME I suppose we have the possibility to use 2 VME slaves, one 
in the AUX board and one in the AMboard, reducing to zero the extra 
signals we have to pass between the 2 and decoupling the 2 designs.
The AMB VME is under discussion and 2 proposals are going to be tried in 
the next prototype:

(1) try to use 64 bit VME transfers.  This implies slave firmware will 
deeply change.
(2) try to use flash rams for the patterns banks.

If we find an agreement about using the 64 or 32 bit transfer, we could 
develop a single  VME slave and use it every where, changing only the 
VME internal addressing. 
Again we should  choose a single responsible that study and propose the  
basic f9irmware for every body, like  we should do it for functions that 
are shared between the AUX board and the final board.

Coming to other details:
we have a 5 bit geographical address to which both the boards have to 
answer (the slot number), however we can choose an extra bit that will 
distinguish between the 2 boards belonging to the same slot.  So we have 
to decide how to share the board addresses.
Unfortunately from what Francesco is learning on the new VME CPU (Atlas 
like), we don't have the possibility to use the entire field of VME 
addresses (32 bits). This is a general problem that will affect also 
Illinois and Fermilab.
It is not totally clear yet, but the use of a large number of address 
bits is strongly discouraged. And more powerful is the VME CPU (more 
memory it has) less VME space is available.
So let's consider the possibility that we have only roughly 20 bits for 
internal addressing.  We will need an internal register to choose 
different memory location fields (Fifos, Spy buffers, AMchips, SS and AM 
Maps, Fit Constant memories.....).

In conclusion we have to plan the VME addressing. I suggest to start 
with a Francesco's description of what he is learning from the CPU use. 
Than we really need to choose a responsible of VME logic if we want to 
create a standard slave.

>     We will need VME access for the AUX card to load the FPGAs, read 
> out the Spy Buffers, etc.  This will presumably come from the AM 
> card.  Have you assigned P3 pins for the VME signals going between the 
> AM and AUX cards?
>                        Regards,
>                        Mel

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