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Re: [802.3_4PPOE] Class Probe Presentation Review

Actually, I think you have the interpretation of “implementation-specific reasons that require reset” correct in principle (it gives permission to do that whenever the PSE wants), but incorrect in terms of function in a standard.


The term “implementation-specific” in a standard is generally code for “outside the scope of the functionality defined in this standard”.  Things like determining whether a PHY receiver is OK are implementation specific, as well as general fail-safes like pse_reset.


If I read “implementation-specific reasons that require reset” to be “whenever the PSE wants”, then, there is no reason for ANY other entry into IDLE than a strict pse_reset, and the result is that the only way the state diagram can inform us when a behavior specified in the standard requires transition to IDLE is by adding a state which sets pse_reset.  In that case, the IDLE state has NO shown input states, and frankly, while simple, it is also clouding the functionality described in the standard.

I don’t see you wanting to do that.


Your concise/generic way has fewer words, but it does so by failing to properly describe specified behavior (even optional behaviors need to be specified) in the standard.


Now, if the issue is that the behavior itself could be accomplished without a transition to IDLE or with a different transition to IDLE, that is another story and we then have to see what that looks like – BUT, if the defined (even optional) behavior in the standard requires a transition from a specified state to IDLE, that arc and the conditions of that ARC should be shown.  [Note, if the behavior is a generic escape from any state into the IDLE, that would probably be handled better by the pse_reset, but that does not appear to be the defined situation].



As far as “conciseness”, I think you’re mistaken – that horse left the building a long time ago.  Right now you have at least the following paths (21 of them?) into IDLE in Figure 145-13:


from DISABLED or TEST_MODE or TEST_ERROR_PRI or TEST_ERROR_SEC or TEST_ERROR_BOTH:                 Pse_enable = enable:


Generic from anywhere:               (Pse_enable = enable) * (pse_reset+iclass_lim_det+error_condition)


from START_CXN_CHCK_DETECT or START_DETECT:                                         Tdet_timer_done


from SISM_START:                          Alt_done_pri*alt_done_sec


from CXN_CHK_EVAL:                    (sig_type=invalid) + tcc2det_timer_done + tdet2det_timer_done


from BACKOFF:                                 Tdbo_timer_done


from DETECT_EVAL:                        ((pse_alternative = both) * ((det_temp = only_one) * (sig_pri ≠ valid) +(det_temp = both_neither) * (sig_sec ≠ valid) + (((CC_DET_SEQ = 0) + (CC_DET_SEQ = 3)) *  (det_temp= only_one) * tdet2det_timer_done)) + (pse_alternative = a) * (sig_pri ≠ valid) +(pse_alternative = b) * (sig_pri = open_circuit)


from CXN_CHK_DETECT_EVAL:  (sig_type = invalid) +(sig_type = single) *((sig_pri ≠ valid) +(sig_sec ≠ valid)) +(sig_type = dual) *(sig_pri ≠ valid) *(sig_sec ≠ valid)


from CLASS_EV2:                             tcle2_timer_done * (pd_class_sig ≠ 4)


from CLASS_EV4 or CLASS_EV5: tcle3_timer_done * (pd_class_sig ≠ temp_var)


from POWER_UP:                            tpon_timer_done


from POWER_ON:                           power_available * tmpdo_timer_done * !(error_pri + error_sec)


from POWER_DENIED:                   UCT


from SEMI_PWRON_SEC:             !error_sec * power_available * tmpdo_timer_done


from ERROR_DELAY:                       ted_timer_done + option_detect_ted




However, this is right.  If it is a defined behavior in the standard, then the arc should be shown.



Let’s deal with the variable, if that is the issue.  I think you’re talking about “option_class_probe_only”, right?  If you’re going to have a defined optional behavior, it is usual to have a variable that says that option is enabled and active.  This happens all over 802.3.  I don’t know how else to do it.  The definition of that variable (“This variable indicates if the PSE should return to IDLE following the completion of do_class_probe.”) I might make a little different to reflect what it is functionally doing, rather than what state transition it makes.  Something like ““This variable is set if the PSE is only to perform a class probe, and not proceed with the classification state diagram.” (heath or others – please refine – the idea is to say what the implemented option is, the state diagram will show that the variable causes a return to IDLE.  The definition tells the reader WHY).



From: Lennart Yseboodt [mailto:lennartyseboodt@xxxxxxxxx]
Sent: Saturday, September 02, 2017 12:36 PM
To: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
Cc: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Class Probe Presentation Review


Hi George,

This is the definition of pse_reset:
Inline image 1

I don't see how we can interpret "implementation-specific reasons that require reset" to mean anything other than "whenever the PSE wants".

What we can probably agree on, is that it is fully OK for a PSE to transition back to IDLE at any time it wants.

We need a mechanism for that. I feel pse_reset is that mechanism.

If others don't see it that way, we should add another variable that allows flipping back into IDLE at any time.

Or change the definition of pse_reset such that it is clear this variable may be used for this purpose.

My specific objection to the IDLE arc in Heaths proposal is that it introduces a new variable, which has no other purpose than to steer the state diagram to IDLE when it reaches a specific state. Having one such construct sends the message that returning to IDLE is not possible, without an explicit arc.

It doesn't matter HOW you get to IDLE, as long as it is allowed to go there no ?

Let's use the most concise/generic way please.

Kind regards,



On Sat, Sep 2, 2017 at 8:00 PM, George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx> wrote:

Yair –

While I agree that we should not be making arcs for all POSSIBLE re-entries to the IDLE state, we should reserve the pse_reset path for ‘implementation specific’ entries, as it is described in the variable.

We SHOULD depict the paths for options specified in the standard in the state diagram – otherwise while there may be a path to interoperable behavior, if we don’t specify that behavior in the state diagram, the behavior described in the state diagram is incomplete.


Are there so many of these options specified in the standard that the state diagram becomes overly complex – I don’t think so, and I certainly hope not.  That would be another issue in itself.  Not capturing behavior specified in the standard in the state diagram isn’t the solution.




From: Yair Darshan [mailto:YDarshan@xxxxxxxxxxxxx]
Sent: Saturday, September 02, 2017 6:01 AM
To: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>; STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_4PPOE] Class Probe Presentation Review




I agree with Lennart that Arcs to IDLE should indicate mandatory transitions to IDLE”. The rest should be done by global pse_reset as we did for the high-level state diagram. Otherwise we will have incomprehensible state machine (return to IDLE from almost every state).


For the dual-sig state diagram there is a comment that addresses it i.e. by adding global pse_ready_pri/sec. See darshan_04_0917.pdf attached that addresses comments i-198 and i-269.






From: George Zimmerman [mailto:george@xxxxxxxxxxxxxxxxxxxx]
Sent: Friday, September 1, 2017 6:08 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Class Probe Presentation Review



Lennart –

I’m not sure I agree with you.  While you could go with a ‘generic’ return to IDLE for any one of a number of things,

if the standard is specifying a particular optional behavior that exits a specific state on a specific condition and returns to IDLE due to that, it should be specified as an arc.


There is a difference between ‘optional behavior’ and ‘proprietary’ or ‘implementation-specific’ behavior which is still compliant to the standard. 


Where I am uncertain is how that return to idle is specified currently in the state diagram.

Right now, I see (page 125, top level diagram) a return from the test-states, and two entries – one from the disabled state, and one conditional on (pse_enable = enable) * (pse_reset + iclass_lim_det + error_condition)


If you are referring to entry into IDLE by means of pse_reset, then the definition of pse_reset wouldn’t imply using it for something like this.  While it allows for “implementation-specific reasons require reset of PSE functionality”, that isn’t what Heath is specifying.



From: Lennart Yseboodt [mailto:lennartyseboodt@xxxxxxxxx]
Sent: Friday, September 01, 2017 1:58 AM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Class Probe Presentation Review


Hi Heath,

1. There is no need to add arcs to IDLE for optional behavior.

The PSE state diagram is at any time allowed to return to IDLE.

As such, the variable option_class_probe_only and the arc from CLASS_PROBE to IDLE are redundant.

2. Your logic for option_class_probe_only coming out of CLASS_PROBE is inverted to the meaning you assigned to it.

I really object to adding optional arcs to IDLE, since if we do this once, we open the floodgates to get arcs from every state to IDLE.

Arcs to IDLE should indicate mandatory transitions to IDLE.


Kind regards,




On Fri, Sep 1, 2017 at 2:33 AM, Heath Stewart <00000855853231d4-dmarc-request@xxxxxxxx> wrote:



As promised we are providing baseline for out class probe presentation from Berlin. Both are attached; root presentation and baseline.


It should be noted that Yair has also identified additional reasons that class probe is useful. I have not yet modified the "justification" portion of the presentation to include his comments - but will. Yair has been very collaborative on this topic.


Please consider this class probe proposal - it has a couple minor changes from what some of you have seen over the last few weeks. Also note that Yair has reflected on my approach and is offering another CLASS_PROBE baseline alternative. 


We've (David and I) tried to keep the scope as narrow as possible in this change as to limit changes to the draft.


  1) Allow class probes to determine class/detect of SS and DS PDs

  2) Limit power dissipated

  3) Ensure power is not applied after class probe by returning to IDLE_XXX

        a) IDLE_XXX will return to main IDLE using existing logic


We've been hesitant to adopt Yair's proposal in preference to this proposal:


  4) Other proposal allows asynchronous return to IDLE_XXX. This can have unintended consequences for tpon and detection sequences becoming unbounded eg you can do whatever you want.

  5) Other proposal creates a CLASS_PROBE(eg short,short,short)->CLASS_RESET->(Long,short,short)->CLASS_RESET->(Long) class event path that is not desirable.


  6) I'm not sure it is useful to have option_class_probe_pri/sec differentiation. If the room feels differently we'll be open to the consideration.





Heath Stewart
Design Center Manager, Mixed Signal

Office   (805) 560-7658
Mobile  (805) 895-0499

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