Data Bus Modelling

[gabriel]

Hi folks,

I've just started exploring SysML, as it could be a new way for the
company I'm working for to design our systems. I apologize, the
vocabulary might not be exact in the following.
I've not seen everything yet but I'm questioning myself on Data Bus
modelisation.

I've got multiple questions:
- Question 1:
Computer 1 sends to Computer 2 an information "simultaneously" on 2
differents media (a CAN Bus and an AFDX bus - Avionics Full-Duplex
Switched Ethernet). From a TopLevel point of view, the interesting
part is to show there is one Flow from Computer1 to Computer2. On
Architecture point of view, this Flow should be associated to 2
differents physical links between those 2 computers.
My first idea is to define a FlowSpec between C1 and C2, and 2 blocks
for each data bus, and allocate the FlowSpec to both media blocks. Is
this allowed ?
Doing this, do I create a "link" between C1, C2 and each data bus ? or
do I need to define an other association between each data bus and C1
and C2 ? In that case, how do I ensure that the link (C1-databus-C2)
is consistent with the FlowSpec ?

- Question 2:
The same system than above is now redunded for some safety reasons.
We've got 4 computers (2 C1 and 2 C2), 2 CAN Busses (one for system 1
and one for system 2), but only one AFDX bus.
How can I model this, not impacting the first model ? The information
on the AFDX bus can't be transfered using the same identifier
(otherwise it would lead to collision). However, there is no such
issue on the CAN bus (since they are segregated)

- Question 3:
content of a databus: how can I describe the encoding, the bit
position, of the Data supported by the FlowSpec and contained on a CAN
Bus message for example ? How do I ensure the consistency between the
message rate and the FlowSpec rate (if this notion exist, I'm not sure
of that), and the positioning consistency (no overlaps on other
data) ?

Does someone know if some Stereotype are already defined to support
Data Bus modeling ?

Sorry for so many questions at a time.

many thanks in advance

gabriel

[ray]

Gabriel,

Although this is not a specific solution, I ran across a system
engineering group at http://public.ccsds.org/publications/SEA.aspx
addressing space data systems. The architecture document gives
extensive viewpoints and conserations for data transmission. It may
be a good source of methods.

Ray


On Dec 22 2008, 2:05 am, gabriel <gabriel.sco...@messier-bugatti.com>
wrote: