Minutes of Weekly Meeting, 2013-04-08

Meeting called to order: 11:07 AM EDT

1. Roll Call

Eric Cormack
Patrick Au
Ian McIntosh
Carl Walker
Peter Horwood
Adam Ley
Harrison Miles
Heiko Ehrenberg
Tim Pender (joined 11:30)

Brian Erickson
Brad Van Treuren

2. Review and approve previous minutes:


  • Heiko had emailed some corrections which Ian had not yet seen. As Heiko was connected via cellphone he was unable to advise the corrections. Ian chose to defer approval until the proposed changes could be reviewed collectively.

3. Review old action items

  • All: do we feel SJTAG is requiring a new test language to obtain the information needed for diagnostics or is STAPL/SVF sufficient? see also Gunnar's presentation, in particular the new information he'd be looking for in a test language
  • Harrison will attempt to come up with a table of use cases and their associated layer and what can be done at that layer. Ongoing.

4. Reminders

  • Consider Adam's three points (from the action from the first weekly meeting) and suggest what is preventing us from answering those questions:
    • Establish consensus on goals and constraints
    • What are we trying to achieve?
    • What restrictions are we faced with?
  • Forum thread for discussion: http://forums.sjtag.org/viewtopic.php?f=3&t=172

5. Discussion Topics

  1. Follow up on Mike Westermeier's slides/Harrison's slides
    • Ian wanted to expand on a point that Harrison had raised at the previous meeting, and felt that the best illustration to work from on this was slide 4 of Harrison's 'SJTAG and Thoughts on the Interface Boundary' pack.
    • {Slide shared}
    • Ian recalled that Harrison had suggested that while 1149.1 might be the main interface used for SJTAG we should be open to others. Additionally, Harrison had also remarked before that the things in his Data Link Layer may not all be at the same level.
    • Ian took these remarks and considered that P1687 and 1581, as examples, both presumed that 1149.1 was the interface of choice to control tests, but it could easily be something else. Harrison agreed and said that would also apply to P1838. Ian then suggested that maybe moved 1149.1, along with any alternatives, into the realms of being a Transport Layer. Harrison thought that might be more akin to the enhancement of the OSI model that merged the Data Link Layer with the Transport Layer and called it simply the Link Layer. Ian was thinking more of a breakout than a merge. Harrison felt that the breakout point was at the Test Step Interface, as it was less coupled to the silicon than the elements below. Harrison was considering a different version of ICL here: While P1687 had ICL for the chip level it still needed someone to come up with a board level ICL.
    • Ian commented that P1687, as currently conceived, stopped at the device boundary and the same was largely true for most of the other standards listed at the Data Link Layer. There is then the established JTAG board tests for manufacturing to test groups of devices attached to a substrate. SJTAG typically operates at a higher level of aggregation again.
    • Harrison remarked that the Test Step Interface might be the next incarnation for P1687, and that the Test Program Interface might be the first step for SJTAG, as at that level you have the notion of named sessions being started and stopped. Ian wondered if that put P1687 outside of its designated scope. Harrison replied that P1687 was initially addressing the silicon level problems and doesn't tackle some of the aspects that 1149.1-2013 has tried to resolve, but an instrument is an instrument and the next step may be a 1687 for the board level to orchestrate instruments on different devices. At this point you don't necessarily care about the TAP and you could easily use USB 3.0 to exploit the bandwidth.
    • Ian felt that there needed to be roadmap for all the emerging standards - without that there was risk that two groups could overlap and solve the same problem in different ways, leading to confusion.
    • Harrison referred to Al Crouch presenting on 1838 and discussing dies that may each employ different standards but all use and elevator protocol to reach the chip boundary.
    • {Tim joined}
    • Harrison reaffirmed his belief that high performance was going to be necessary for SJTAG. Ian felt that maybe wasn't true for things like conventional interconnect tests, but he could see that instruments that may be trying measure performance or are transacting 'real data' might benefit from higher bandwidths.
    • Ian remarked that part of his objective in this discussion was to test where the bottom end of SJTAG was in relation to the protocol stack. He didn't feel that SJTAG was constrained going up the stack. This is why he was considering whether 1149.1 needed to sit in a layer of its own - SJTAG interfaces to 1149.1 (or its alternatives) and not to any of the other standards. Harrison's suggestion of the Link Layer made him want to think about this some more.
    • Harrison thought that Brad had the right idea in introducing namespaces: Vectors, for SJTAG, are really flow indicators associated with sessions and care how they're transported. SJTAG doesn't need to worry about the vectors applied to the devices. The vector flow can apply across multiple boards or multiple instances of a single board so namespaces become very important.
    • Ian noted that Harrison's slides were a work in progress and asked if he was likely to update them. Harrison felt there were some thoughts that came out of this meeting that he could try to capture. {ACTION}

6. Key Takeaway for today's meeting

  1. Test Steps don't care about how the vectors it uses are transported.
  2. There may need to be some coordination with other standards to avoid overlapping scopes*.

*Heiko noted that by the time SJTAG moves towards a standard P1687 will most likely be approved.

7. Schedule next meeting

Next Meeting:
April 15.

April schedule:

8. Any other business


9. Review new action items

    <li?Harrison: Update slide pack to incorporate recently discussed ideas.

10. Adjourn

Eric moved to adjourn at 11:49 AM EDT, seconded by Peter.

Respectfully submitted,
Ian McIntosh