1. SpaceWire Rev. 1 - REST Panel
Felix Siegle
13/09/2017

2. REST Panel Chaired by me since meeting #9 (April 2017).
Very active and lively panel with participants from:
Airbus DS, France and Germany (Olivier Notebaert and Paul Rastetter)
Thales Alenia Space, France (Brice Dellandrea)
RUAG Space, Sweden (Torbjörn Hult)
STAR-Dundee / UoD, UK (Stuart Mills)
4Links, UK (Roger Peel and Paul Walker)

3. Current status
The REST panel deals with all topics that are not related to the physical layer.
Altogether, 339 DRRs were received for these topics.
In Yokohama, the working group decided to use the May version of the standard (draft F1-7) as the new baseline rather than the public review version.
94 out of 339 DRRs do not apply to the May version and could thus be closed.

4. Some statistics Level of agreement Number of DRRs 0/7 1/7 2/7 3/7 4/7
1/7
2/7
3/7
4/7 5
5/7 14
6/7
128
7/7
192

5. Next steps Get 100% agreement on all DRRs.
All changes required (including the ones introduced by the REST panel) will be annotated in a Word file and sent to the editor Steve Parkes.
Decisions will be justified and answers formulated.
The answers will be sent out to the initiators of the DRRs.
Due to rolling back to the May version of the standard, another public review might be required depending on ECSS secretariat decision.
Initiators unsatisfied with the handling of their DRRs can use this second public review to enter an objection.

6. Changes introduced by the REST panel
Introduced more consistency, e.g:
Disabled flag was renamed to LinkDisabled.
Enabled flag was fully removed, which allows us to remove awkward formulations such as: “when the port is disabled (enable de-asserted)”  “when LinkDisabled is asserted”
PortReset is now listed as a management parameter.

7. Changes introduced by the REST panel
State machine description was improved:
The state machine is now described in an ‘ideal’ way. For example, so far the connecting state was split into two states: before an FCT is received and after an FCT is received. However, if an FCT is received, the state machine should immediately move to the run state!
Enter conditions were removed from the textual state descriptions as they were redundant to the exit conditions of the other states and not even always consistent.

8. Main changes introduced by the REST panel
State machine description was improved:
Mistakes in the data flow were corrected, for example in the Run state:
1. Enable sending of FCTs, N-Chars and broadcast codes.
2. Pass Nulls to the Encoding Layer when there is nothing to send.
3. Assert the Receive Enable control flag.
4. Pass received N-Chars and broadcast codes to the Encoding Layer.
5. Pass any received broadcast codes to the Network Layer.
6. If and when required, change the SpaceWire output port operating rate (see clause 5.4.3).
1. assert the Transmit Enable control flag, and send broadcast codes, FCTs, N-Chars and Nulls; following the rules described in clause ;
2. assert the Receive Enable control flag;
3. store any N-Chars received from the Encoding Layer in the RX FIFO and register any broadcast codes received from the Encoding Layer;
4. if and when required, change the SpaceWire output port operating rate (see clause 5.4.9).

9. Main changes introduced by the REST panel
State machine description was improved:
The diagram is now in black/white with new conditions underlined.
Some mistakes in the diagram were corrected, e.g. broadcast codes instead of time-codes.
The “alternative behavior when LinkDisabled asserted” clause was fully removed (no need for backwards-compliance).
Differences to the old state machine have been captured in a new NOTE.

10. Main changes introduced by the REST panel
Potentially confusing and erroneous information was removed, e.g.:
Data disappeared?
Good for a handbook but not required in the standard.

11. Open points for discussion
Service interfaces requirements, e.g. SEND_PACKET.request etc.
Should we move them to an informative annex?
Distributed Interrupts: When was the decision made and what is the rationale behind only using 32-bit interrupts with acknowledgements?
Distributed Interrupts: Timeout values are critical – Shall we clearly define that these values are configuration parameters?
Backward-compatibility vs. Backward-compliance

12. - Thank you -