Thepdstatediagramspecifiestheexternallyobservablebehaviorofapd.Thepdshallprovidethe

33.3.3PDstatediagram

ThePDstatediagramspecifiestheexternallyobservablebehaviorofaPD.ThePDshallprovidethe behaviorofthestatediagramshowninFigure33–16.

33.3.3.1Conventions

Thenotationusedinthe statediagramfollowsthe conventionsofstatediagramsasdescribedin21.5.

33.3.3.2Constants

ThePDstatediagramusesthefollowingconstants: VReset_th

Resetvoltagethreshold(seeTable33–17)

VMark_th

Markeventvoltagethreshold(seeTable33–17)

class_sig

PDclassification,oneofeither0,1, 2,3,or4(seeTable33–16)

33.3.3.3Variables

ThePDstatediagramusesthefollowingvariables:

mdi_power_required

AcontrolvariableindicatingthePDisenabledandshouldrequestpowerfromthePSEby applying aPDdetection signature tothelink,andwhenthePSEsourcespowertoapplytheMPS tokeepthePSEsourcingpower.A variable thatis set inan implementation-dependent manner.Values: FALSE: PDfunctionalityisdisabled.

TRUE:PDfunctionalityisenabled.

pd_2multi-event

A controlvariableindicatingwhetherthePDpresentsa 2Mulitple-Eventclasssignature.

Values:FALSE:PDdoesnotpresenta2Multiple-Eventclasssignature.

TRUE:PDdoespresenta Mulitple2-Eventclasssignature.

pd_dll_capable

ThisvariableindicateswhetherthePDimplementsDataLinkLayerclassification. Values:FALSE: ThePDdoesnotimplementDataLinkLayerclassification.

TRUE:ThePDdoesimplementDataLinkLayerclassification.

pd_dll_enabled

A variableindicatingwhethertheDataLinkLayerclassificationmechanismisenabled.Values:FALSE: DataLinkLayerclassificationis notenabled.

TRUE:DataLinkLayerclassificationis enabled.

pd_max_power

AcontrolvariableindicatingthemaxpowerthatthePDmaydrawfromthePSE.Seepower classificationsinTable33–18.

Values:0:PDmaydrawClass0 power

1:PDmaydrawClass1 power

2:PDmaydrawClass2 power

3:PDmaydrawClass3 power

4:PDmaydrawClass4 power

5:PD may draw Class 5 power

6:PD may draw Class 6 power

7:PD may draw Class 7 power

pd_reset

Animplementation-specificcontrolvariablethatunconditionallyresetsthePDstatediagramtothe

OFFLINEstate.

Values:FALSE:Thedevicehasnotbeenreset(default).

TRUE:Thedevicehasbeenreset.

power_received

AnindicationfromthecircuitrythatpowerispresentonthePD’sPI.

Values:FALSE:TheinputvoltagedoesnotmeettherequirementsofVPort_PDinTable33–18.

TRUE:Theinputvoltagemeetstherequirementsof VPort_PD. present_class_sig_A

Controlspresentingthe classificationsignaturethat is used during the first two class events(see33.3.5)bythePD.

Values:FALSE:ThePDclassificationsignatureisnottobeappliedtothelink.

TRUE:ThePDclassificationsignatureistobeappliedtothelink.

present_class_sig_B

Controls presenting the classification signature during the 3rd class event and all subsequent class events (see 33.3.5) by the PD.

Values:FALSE:The PD classification signature is not to be applied to the link.

TRUE:The PD classification signature is to be applied to the link.

present_det_sig

Controlspresentingthedetectionsignature(see33.3.4)bythePD.

Values:FALSE:Anon-validPDdetectionsignatureistobeappliedtothelink.

TRUE:AvalidPDdetectionsignatureis tobeappliedtothelink. present_mark_sig

Controlspresentingthemarkeventcurrentandimpedance(see33.3.5.2.1)bythePD. Values:FALSE: ThePDdoesnotpresentmarkeventbehavior.

TRUE:ThePDdoespresentmarkeventbehavior.

present_mps

ControlsapplyingMPS(see33.3.8)tothePD’sPI.

Values:FALSE:TheMaintainPowerSignature(MPS)isnottobeappliedtothePD’sPI.

TRUE:TheMPSistobeappliedtothePD’sPI. pse_dll_power_leveltype

Acontrolvariableoutput bythePDpower controlstatediagram(Figure33–28)thatindicatesthe typeofPSEbywhichthePDisbeingpowered.

Values:1:ThePSEisa Type1 PSE(default).

2:ThePSEis a Type 2 PSE.

3:The PSE is a Type 3 PSE.

4:The PSE is a Type 4 PSE.

pse_power_type

A control variable that indicates to the PD the type of PSE by which it is being powered.Values:1: The PSE is a Type 1 PSE.

2:The PSE is a Type 2 PSE.

pse_power_level

A control variable that indicates to the PD the level of power the PSE is supplying.

Values:1:The PSE is delivering the PD’s requested power or 15.4W, whichever is less.

2:The PSE is delivering the PD’s requested power or 30W, whichever is less.

3:The PSE is delivering the PD’s requested power or 60W, whichever is less.

4:The PSE is delivering the PD’s requested power or 90W (TBD), whichever is less.

VPD

Voltageat thePDPIasdefinedin1.4.

33.3.3.4Timers

Alltimersoperateinthemannerdescribedin14.2.3.2withthefollowingaddition.Atimerisresetandstops countinguponenteringastatewhere“stopx_timer”is asserted.

tpowerdly_timer

AtimerusedtopreventtheType2PDfromdrawingmorethaninrushcurrentduringthePSE’s inrushperiod;seeTdelayinTable33–18.

33.3.3.5 Functions

do_class_timing

This function is used by a Type 3 or Type 4 PD to evaluate the type of PSE connected to the link by measuring the length of the classification event. The classification event timing requirements are defined in Table 33-10. This function returns the following variable:

Type_3_MPS: A control variable that indicates to the PD the Type of PSE to which it is connected. This variable is used to indicate which MPS timing requirements (see 33.3.8). the PD should use.

Values:TRUE:The PSE uses Type 3 MPS requirements.

FALSE:The PSE uses Type 1 MPS requirements.

33.3.3.65Statediagrams

Figure33–16—PDstatediagram

Figure33–16—PDstatediagram(continued)

NOTE1—DO_CLASS_EVENT36createsadefinedbehaviorforaType2, Type 3, or Type 4PDthatisbroughtintotheclassificationrange repeatedly.

NOTE2—Ingeneral,thereisnorequirementforaPDtorespondwithavalidclassificationsignatureforany

DO_CLASS_EVENTdurationlessthanTclass.

33.3.5PDclassifications

See33.2.6fora generaldescriptionofclassificationmechanisms.

A PDmaybeclassifiedbythePSEbasedonthePhysicalLayerclassificationinformation,DataLinkLayer classification, oracombinationofbothprovidedbythePD.TheintentofPDclassificationistoprovide informationaboutthemaximumpowerrequiredbythePDduringoperation. Additionally,classificationis usedtoestablishmutualidentificationbetweenType2, Type 3, and Type 4 PSEsandType2, Type3, and Type 4 PDs.

ThemethodofclassificationdependsonthetypeofthePDandthetypeoftheattachedPSE. A PDshallmeetat leastoneof theallowableclassificationpermutationslistedinTable33–8. AType1PDmayimplementanyoftheclasssignaturesin33.3.5and33.6.

Type2, Type 3, and Type 4PDsimplementboth2Multiple-Eventclasssignature(see33.3.5.2)andDataLinkLayerclassification(see33.6).

PDclassificationbehaviorconformstothestatediagraminFigure33–16.

33.3.5.1PD1-Eventclasssignature

Class0 is thedefaultforPDs.However,toimprovepowermanagementat thePSE,a Type1 PDmayoptto providea signatureforClass1 to3.

ThePDisclassifiedbasedonpower.ThePhysicalLayerclassificationofthePDisthemaximumpowerthat thePDdrawsacrossallinputvoltagesandoperationalmodes.

PDsimplementing aMulitple2-EventclasssignatureshallreturnClass4inaccordancewiththemaximumpower draw,PClass_PD,asspecifiedinTable33–18.Since1-Eventclassification isasubsetof2Multiple-Event classification,Type2, Type 3, and Type 4PDsrespondto1-EventclassificationwithaClass4signature.Type1PDsmaychoosetoimplement aMultiple2-EventclasssignatureandreturnClass0,1,2,or3inaccordance withthe maximumpowerdraw,PClass_PD.The Type2, Type 3, and Type 4PD’sclassificationbehaviorshallconformtotheelectrical specificationsdefinedbyTable33–17.

Inadditiontoavaliddetectionsignature,PDsshallprovidethecharacteristicsofaclassificationsignatureas specifiedinTable33–16.AType 1 and Type 2PDsshallpresentone,andonlyone,classificationsignatureduringclassification.

Table33–16—Classificationsignature1,measuredatPDinputconnector

33.3.5.2PD2Multiple-Eventclasssignature

PDs implementing Multiple-Event Physical Layer classification shall present class_sig_A during CLASS_EV1 and CLASS_EV2 and class_sig_B during CLASS_EV3, CLASS_EV4, CLASS_EV5, and CLASS_EV6. PDs implementing a 2-Event class signature shall return a Class 4 classification signature in accordance with the maximum power draw, PClass_PD, as specified by Table 33–18. ThePD’sclassification behaviorshall conformtotheelectricalspecificationsdefinedbyTable33–17.

Table33–TBDA1—Multiple-Event Physical Layer Classification Responses

*NOTE: See Table 33-16 for definitions of class signatures 1-4.

Untilsuccessful2Multipile-EventPhysicalLayerclassification orDataLinkLayerclassificationhascompleted,a Type2, Type 3, or Type 4PD’spse_power_leveltypestatevariableissetto‘1.’AType2, Type 3, or Type 4PDshallconformtotheelectrical requirementsasdefinedbyTable33–18fortheleveltypedefinedinitspse_power_leveltypestatevariable.

Table33–17—Multiple2-EventPhysicalLayerclassificationelectricalrequirements

33.3.5.2.1MarkEventbehavior

WhenthePDispresentingamarkeventsignatureasshowninthestatediagramofFigure33–16,thePDshalldrawIMarkasdefinedinTable33–17andpresentanon-validdetectionsignatureasdefinedinTable33–15.

ThePDshallnotexceedtheIMarkcurrentlimitswhenvoltageatthePIenterstheVMarkspecificationas definedinTable33–17.

VMark_thisthePIvoltagethresholdatwhichthePDimplementing 2Multiple-Eventclasssignaturetransitionsinto andoutoftheDO_CLASS_EVENT1,or DO_CLASS_EVENT2, DO_CLASS_EVENT3, DO_CLASS_EVENT4, or DO_CLASS_EVENT5statesasshowninFigure33–16.

ThePDshalldrawIMarkuntilthePDtransitionsfroma DO_MARK_EVENTstatetotheIDLEstate. VReset_this thePIvoltagethresholdatwhichthePDimplementing2Multiple-EventclasssignaturetransitionsfromaDO_MARK_EVENTstatetotheIDLEstateasshowninFigure33–16.

33.3.6PSETypeidentification

A Type2 PDshallidentifythePSETypeaseitherType1 orType2(seeFigure33–16). A Type 3 PD shall identify the PSE Type as either Type 1, Type 2, or Type 3. A Type 4 PD shall identify the PSE Type as either Type 1, Type 2, Type 3, or Type 4.

Thedefaultvalueofpse_power_leveltypeis1.Afterasuccessful2Multiple-EventPhysicalLayerclassificationorDataLinkLayerclassificationhascompleted,thepse_power_leveltypeissettoeither 2, 3 or, 4.

ThePDresetsthepse_power_leveltypeto‘1’whenthePDenterstheDO_DETECTIONstate.

33.3.7PDpower

ThepowersupplyofthePDshalloperatewithinthecharacteristicsinTable33–18.

ThePDmaybecapableofdrawingpowerfromalocalpowersource.Whenalocalpowersourceis provided,thePDmaydrawsome,none,orallofitspowerfromthePI.

Table33–18—PDpowersupplylimits

Table33–18—PDpowersupplylimits(continued)