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Text File | 1990-03-09 | 109KB | 2,326 lines

.RR--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--!--! .PL 62 .LM 1 .RM 78 .MT3 .MB4 .HM1 .FM1 .PO10 .CW10 .SR2 .UJ0 .OJ0 .UL1 .heLogical Characteristics 3/9/90 .foSCSI-2 draft proposed American National Standard 5-# Revision 10c .pn 1 .cp 30 .aw off .pm 0 5. Logical Characteristics .aw on .pm 3 .cp 20 .aw off .pm 0 5.1. SCS╔ Bu≤ Phases .aw on .pm 3 ááThσ SCS╔ architecturσ include≤ eigh⌠ distinc⌠ phases: ááBU╙ FRE┼ phase ááARBITRATIO╬ phase ááSELECTIO╬ phase ááRESELECTIO╬ phase ááCOMMAN─ phasσ \ ááDAT┴ phasσ ▄ Thesσ phase≤ arσ collectivel∙ termeΣ the ááSTATU╙ phasσ » informatioε transfe≥ phases. ááMESSAG┼ phasσ / ááThσ SCS╔ bu≤ caε neve≥ bσ iε morσ thaε onσ phasσ a⌠ an∙ giveε time« Iε thσ ì followinτ descriptions¼ signal≤ tha⌠ arσ no⌠ mentioneΣ shal∞ no⌠ bσ asserted. .cp 10 .aw off .pm 0 5.1.1. BU╙ FRE┼ Phase .aw on .pm 3 ááThσ BU╙ FRE┼ phasσ i≤ useΣ t∩ indicatσ tha⌠ n∩ SCS╔ devicσ i≤ activel∙ usinτ ì thσ SCS╔ bu≤ anΣ tha⌠ i⌠ i≤ available« Iε somσ case≤ ß targe⌠ revert≤ t∩ BU╙ ì FRE┼ phasσ t∩ indicatσ aε erro≥ conditioε tha⌠ i⌠ ha≤ n∩ othe≥ wa∙ t∩ handle« ì Thi≤ i≤ calleΣ a≤ aε unexpecteΣ disconnect. ááSCS╔ device≤ shal∞ detec⌠ thσ BU╙ FRE┼ phasσ afte≥ thσ SE╠ anΣ BS┘ signal≤ ì arσ botΦ falsσ fo≥ a⌠ leas⌠ ß bu≤ settlσ delay. ááSCS╔ device≤ shal∞ releasσ al∞ SCS╔ bu≤ signal≤ withiε ß bu≤ clea≥ dela∙ ì afte≥ thσ BS┘ anΣ SE╠ signal≤ becomσ continuousl∙ falsσ fo≥ ß bu≤ settlσ ì delay« Iµ aε SCS╔ devicσ require≤ morσ thaε ß bu≤ settlσ dela∙ t∩ detec⌠ thσ ì BU╙ FRE┼ phasσ theε i⌠ shal∞ releasσ al∞ SCS╔ bu≤ signal≤ withiε ß bu≤ clea≥ ì dela∙ minu≤ thσ exces≤ timσ t∩ detec⌠ thσ BU╙ FRE┼ phase« Thσ tota∞ timσ t∩ ì clea≥ thσ SCS╔ bu≤ shal∞ no⌠ exceeΣ ß bu≤ settlσ dela∙ plu≤ ß bu≤ clea≥ delay. ááInitiator≤ normall∙ d∩ no⌠ expec⌠ BU╙ FRE┼ phasσ t∩ begiε becausσ oµ thσ ì target'≤ releasσ oµ thσ BS┘ signa∞ excep⌠ afte≥ onσ oµ thσ followinτ ì occurrences: áá(1⌐ afte≥ ß rese⌠ conditioε i≤ detected. áá(2⌐ afte≥ aε ABOR╘ messagσ i≤ successfull∙ receiveΣ b∙ ß target. áá(3⌐ afte≥ ß BU╙ DEVIC┼ RESE╘ messagσ i≤ successfull∙ receiveΣ b∙ ß target. áá(4⌐ afte≥ ß DISCONNEC╘ messagσ i≤ successfull∙ transmitteΣ froφ ß targe⌠ ì (seσ 5.6.6) áá(5⌐ afte≥ ß COMMAN─ COMPLET┼ messagσ i≤ successfull∙ transmitteΣ froφ ß ì targe⌠ (seσ 5.6.5). áá(6⌐ afte≥ ß RELEAS┼ RECOVER┘ messagσ i≤ successfull∙ receiveΣ b∙ ß target. áá(7⌐ afte≥ aε ABOR╘ TA╟ messagσ i≤ successfull∙ receiveΣ b∙ ß target. áá(8⌐ afte≥ ß CLEA╥ QUEU┼ messagσ i≤ successfull∙ receiveΣ b∙ ß target. .lm 1 ááThσ BU╙ FRE┼ phasσ ma∙ als∩ bσ entereΣ afte≥ aε unsuccessfu∞ selectioε o≥ ì reselection¼ althougΦ iε thi≤ casσ i⌠ i≤ thσ releasσ oµ thσ SE╠ signa∞ rathe≥ ì thaε thσ releasσ oµ thσ BS┘ signa∞ tha⌠ firs⌠ establishe≤ thσ BU╙ FRE┼ phase. ááIµ aε initiato≥ detect≤ thσ releasσ oµ thσ BS┘ signa∞ b∙ thσ targe⌠ a⌠ an∙ ì othe≥ time¼ thσ targe⌠ i≤ indicatinτ aε erro≥ conditioε t∩ thσ initiator« Thσ ìètarge⌠ ma∙ perforφ thi≤ transitioε t∩ thσ BU╙ FRE┼ phasσ independen⌠ oµ thσ ì statσ oµ thσ AT╬ signal« Thσ initiato≥ shal∞ managσ thi≤ conditioε a≤ aε ì unsuccessfu∞ I/╧ proces≤ termination« Thσ targe⌠ terminate≤ thσ I/╧ proces≤ ì b∙ clearinτ al∞ pendinτ datß anΣ statu≤ informatioε fo≥ thσ affecteΣ logica∞ ì uni⌠ o≥ targe⌠ routine« Thσ targe⌠ ma∙ optionall∙ preparσ sensσ datß tha⌠ ma∙ ì bσ retrieveΣ b∙ ß REQUES╘ SENS┼ command« Wheε aε initiato≥ detect≤ aε ì unexpecteΣ disconnect¼ i⌠ i≤ recommendeΣ tha⌠ ß REQUES╘ SENS┼ commanΣ bσ ì attempteΣ t∩ obtaiε an∙ valiΣ sensσ datß tha⌠ ma∙ bσ available. .cp 10 .aw off .pm 0 5.1.2. ARBITRATIO╬ Phase .aw on .pm 3 ááThσ ARBITRATIO╬ phasσ allow≤ onσ SCS╔ devicσ t∩ gaiε contro∞ oµ thσ SCS╔ bu≤ ì s∩ tha⌠ i⌠ caε initiatσ o≥ resumσ aε I/╧ process. ááThσ procedurσ fo≥ aε SCS╔ devicσ t∩ obtaiε contro∞ oµ thσ SCS╔ bu≤ i≤ a≤ ì follows: áá(1⌐ Thσ SCS╔ devicσ shal∞ firs⌠ wai⌠ fo≥ thσ BU╙ FRE┼ phasσ t∩ occur« Thσ ì BU╙ FRE┼ phasσ i≤ detecteΣ wheneve≥ botΦ thσ BS┘ anΣ SE╠ signal≤ arσ ì simultaneousl∙ anΣ continuousl∙ falsσ fo≥ ß minimuφ oµ ß bu≤ settlσ delay. .lm 3 ááIMPLEMENTOR╙ NOTE║ Thi≤ bu≤ settlσ dela∙ i≤ necessar∙ becausσ ß ì áátransmissioε linσ phenomenoε knowε a≤ ß "wireΣ-O╥ glitchó ma∙ causσ thσ BS┘ ì áásigna∞ t∩ briefl∙ appea≥ false¼ eveε thougΦ i⌠ i≤ beinτ driveε true. .lm 1 áá(2⌐ Thσ SCS╔ devicσ shal∞ wai⌠ ß minimuφ oµ ß bu≤ freσ dela∙ afte≥ detectioε ì oµ thσ BU╙ FRE┼ phasσ (i.e« afte≥ thσ BS┘ anΣ SE╠ signal≤ arσ botΦ falsσ fo≥ ß ì bu≤ settlσ delay⌐ beforσ drivinτ an∙ signal. áá(3⌐ Followinτ thσ bu≤ freσ dela∙ iε Ste≡ (2)¼ thσ SCS╔ devicσ ma∙ arbitratσ ì fo≥ thσ SCS╔ bu≤ b∙ assertinτ botΦ thσ BS┘ signa∞ anΣ it≤ owε SCS╔ ID¼ howeve≥ ì thσ SCS╔ devicσ shal∞ no⌠ arbitratσ (i.e« asser⌠ thσ BS┘ signa∞ anΣ it≤ SCS╔ ì ID⌐ iµ morσ thaε ß bu≤ se⌠ dela∙ ha≤ passeΣ sincσ thσ BU╙ FRE┼ phasσ wa≤ las⌠ ì observed« .lm 3 ááIMPLEMENTOR╙ NOTE║ Therσ i≤ n∩ maximuφ dela∙ beforσ assertinτ thσ BS┘ ì áásigna∞ anΣ thσ SCS╔ I─ followinτ thσ bu≤ freσ dela∙ iε Ste≡ (2⌐ a≤ lonτ a≤ ì ááthσ bu≤ remain≤ iε thσ BU╙ FRE┼ phase« However¼ SCS╔ device≤ tha⌠ dela∙ ì áálonge≥ thaε ß bu≤ settlσ dela∙ plu≤ ß bu≤ se⌠ dela∙ froφ thσ timσ wheε thσ ì ááBS┘ anΣ SE╠ signal≤ firs⌠ becomσ falsσ ma∙ fai∞ t∩ participatσ iε ì ááarbitratioε wheε competinτ witΦ faste≥ SCS╔ devices. .lm 1 .cp 10 áá(4⌐ Afte≥ waitinτ a⌠ leas⌠ aε arbitratioε dela∙ (measureΣ froφ it≤ assertioε ì oµ thσ BS┘ signal⌐ thσ SCS╔ devicσ shal∞ examinσ thσ DAT┴ BUS« Iµ ß highe≥ ì priorit∙ SCS╔ I─ bi⌠ i≤ truσ oε thσ DAT┴ BU╙ (DB(7⌐ i≤ thσ highest)¼ theε thσ ì SCS╔ devicσ ha≤ los⌠ thσ arbitratioε anΣ thσ SCS╔ devicσ ma∙ releasσ it≤ ì signal≤ anΣ returε t∩ Ste≡ (1)« Iµ n∩ highe≥ priorit∙ SCS╔ I─ bi⌠ i≤ truσ oε ì thσ DAT┴ BUS¼ theε thσ SCS╔ devicσ ha≤ woε thσ arbitratioε anΣ i⌠ shal∞ asser⌠ ì thσ SE╠ signal« An∙ SCS╔ devicσ othe≥ thaε thσ winne≥ ha≤ los⌠ thσ ì arbitratioε anΣ shal∞ releasσ thσ BS┘ signa∞ anΣ it≤ SCS╔ I─ bi⌠ withiε ß bu≤ ì clea≥ dela∙ afte≥ thσ SE╠ signa∞ become≤ true« Aε SCS╔ devicσ tha⌠ lose≤ ì arbitratioε ma∙ returε t∩ Ste≡ (1). .cp 3 .lm 3 ááIMPLEMENTOR╙ NOTE║ I⌠ i≤ recommendeΣ tha⌠ ne≈ implementation≤ wai⌠ fo≥ thσ ì ááSE╠ signa∞ t∩ becomσ truσ beforσ releasinτ thσ BS┘ signa∞ anΣ SCS╔ I─ bi⌠ ì ááwheε arbitratioε i≤ lost. .. Rationale: Creates fewer wired-OR glitches and may assist arbitration fair- .. ness algorithms. .lm 1 è.cp 3 áá(5⌐ Thσ SCS╔ devicσ tha⌠ win≤ arbitratioε shal∞ wai⌠ a⌠ leas⌠ ß bu≤ clea≥ ì dela∙ plu≤ ß bu≤ settlσ dela∙ afte≥ assertinτ thσ SE╠ signa∞ beforσ changinτ ì an∙ signals. .cp 5 .lm 3 ááNOTE║ Thσ SCS╔ I─ bi⌠ i≤ ß singlσ bi⌠ oε thσ DAT┴ BU╙ tha⌠ correspond≤ t∩ ì ááthσ SCS╔ device'≤ uniquσ SCS╔ address« Al∞ othe≥ seveε DAT┴ BU╙ bit≤ shal∞ ì áábσ releaseΣ b∙ thσ SCS╔ device« Parit∙ i≤ no⌠ valiΣ durinτ thσ ARBITRATIO╬ ì ááphase« Durinτ thσ ARBITRATIO╬ phase¼ DB(P⌐ ma∙ bσ releaseΣ o≥ asserted¼ bu⌠ ì ááshal∞ no⌠ bσ activel∙ driveε false. .lm 1 .cp 10 .aw off .pm 0 5.1.3. SELECTIO╬ Phase .aw on .pm 3 ááThσ SELECTIO╬ phasσ allow≤ aε initiato≥ t∩ selec⌠ ß targe⌠ fo≥ thσ purposσ ì oµ initiatinτ somσ targe⌠ functioε (e.g.¼ REA─ o≥ WRIT┼ command)« Durinτ thσ ì SELECTIO╬ phasσ thσ I/╧ signa∞ i≤ negateΣ s∩ tha⌠ thi≤ phasσ caε bσ ì distinguisheΣ froφ thσ RESELECTIO╬ phase. ááThσ SCS╔ devicσ tha⌠ woε thσ arbitratioε ha≤ botΦ thσ BS┘ anΣ SE╠ signal≤ ì asserteΣ anΣ ha≤ delayeΣ a⌠ leas⌠ ß bu≤ clea≥ dela∙ plu≤ ß bu≤ settlσ dela∙ ì beforσ endinτ thσ ARBITRATIO╬ phase« Thσ SCS╔ devicσ tha⌠ woε thσ arbitratioε ì become≤ aε initiato≥ b∙ no⌠ assertinτ thσ I/╧ signal« ááThσ initiato≥ shal∞ se⌠ thσ DAT┴ BU╙ t∩ ß valuσ whicΦ i≤ thσ O╥ oµ it≤ SCS╔ ì I─ bi⌠ anΣ thσ target'≤ SCS╔ I─ bi⌠ anΣ i⌠ shal∞ asser⌠ thσ AT╬ signa∞ ì (indicatinτ tha⌠ ß MESSAG┼ OU╘ phasσ i≤ t∩ follo≈ thσ SELECTIO╬ phase)« Thσ ì initiato≥ shal∞ theε wai⌠ a⌠ leas⌠ tw∩ deske≈ delay≤ anΣ releasσ thσ BS┘ ì signal« Thσ initiato≥ shal∞ theε wai⌠ a⌠ leas⌠ ß bu≤ settlσ dela∙ beforσ ì lookinτ fo≥ ß responsσ froφ thσ target. ááThσ targe⌠ shal∞ determinσ tha⌠ i⌠ i≤ selecteΣ wheε thσ SE╠ signa∞ anΣ it≤ ì SCS╔ I─ bi⌠ arσ truσ anΣ thσ BS┘ anΣ I/╧ signal≤ arσ falsσ fo≥ a⌠ leas⌠ ß bu≤ ì settlσ delay« Thσ selecteΣ targe⌠ ma∙ examinσ thσ DAT┴ BU╙ iε orde≥ t∩ ì determinσ thσ SCS╔ I─ oµ thσ selectinτ initiator« Thσ selecteΣ targe⌠ shal∞ ì theε asser⌠ thσ BS┘ signa∞ withiε ß selectioε abor⌠ timσ oµ it≤ mos⌠ recen⌠ ì detectioε oµ beinτ selected╗ thi≤ i≤ requireΣ fo≥ correc⌠ operatioε oµ thσ ì selectioε timσ-ou⌠ procedure« ááThσ targe⌠ shal∞ no⌠ responΣ t∩ ß selectioε iµ baΣ parit∙ i≤ detected« ì Also¼ iµ morσ thaε tw∩ SCS╔ I─ bit≤ arσ oε thσ DAT┴ BUS¼ thσ targe⌠ shal∞ no⌠ ì responΣ t∩ selection. .lm 3 ááIMPLEMENTOR╙ NOTE║ Iµ ß targe⌠ choose≤ t∩ suppor⌠ thσ singlσ initiato≥ o≥ ì ááselectioε withou⌠ assertinτ AT╬ option≤ oµ SCS╔-1¼ i⌠ ma∙ responΣ a≤ ì áádescribeΣ iε thσ SCS╔-▒ standard. .lm 1 ááN∩ les≤ thaε tw∩ deske≈ delay≤ afte≥ thσ initiato≥ detect≤ thσ BS┘ signa∞ i≤ ì true¼ i⌠ shal∞ releasσ thσ SE╠ signa∞ anΣ ma∙ changσ thσ DAT┴ BUS« Thσ targe⌠ ì shal∞ wai⌠ unti∞ thσ SE╠ signa∞ i≤ falsσ beforσ assertinτ thσ RE╤ signa∞ t∩ ì ente≥ aε informatioε transfe≥ phase. .cp 5 .aw off .pm 0 5.1.3.1. SELECTION Time-out Procedurσ .aw on .pm 3 ááTw∩ optiona∞ selectioε timσ-ou⌠ procedure≤ arσ specifieΣ fo≥ clearinτ thσ ì SCS╔ bu≤ iµ thσ initiato≥ wait≤ ß minimuφ oµ ß selectioε timσ-ou⌠ dela∙ anΣ ì therσ ha≤ beeε n∩ BS┘ signa∞ responsσ froφ thσ target: áá(1⌐ Optionally¼ thσ initiato≥ shal∞ asser⌠ thσ RS╘ signa∞ (seσ 5.2.2).èáá(2⌐ Optionally¼ thσ initiato≥ shal∞ continuσ assertinτ thσ SE╠ anΣ AT╬ ì signal≤ anΣ shal∞ releasσ thσ DAT┴ BUS« Iµ thσ initiato≥ ha≤ no⌠ detecteΣ thσ ì BS┘ signa∞ t∩ bσ truσ afte≥ a⌠ leas⌠ ß selectioε abor⌠ timσ plu≤ tw∩ deske≈ ì delays¼ thσ initiato≥ shal∞ releasσ thσ SE╠ anΣ AT╬ signal≤ allowinτ thσ SCS╔ ì bu≤ t∩ g∩ t∩ thσ BU╙ FRE┼ phase« SCS╔ device≤ shal∞ ensurσ tha⌠ wheε ì respondinτ t∩ selectioε tha⌠ thσ selectioε wa≤ stil∞ valiΣ withiε ß selectioε ì abor⌠ timσ oµ thei≥ assertioε oµ thσ BS┘ signal« Failurσ t∩ compl∙ witΦ thi≤ ì requiremen⌠ coulΣ resul⌠ iε aε imprope≥ selectioε (tw∩ target≤ connecteΣ t∩ ì thσ samσ initiator¼ wronτ targe⌠ connecteΣ t∩ aε initiator¼ o≥ ß targe⌠ ì connecteΣ t∩ n∩ initiator). .lm 1 .cp 10 .aw off .pm 0 5.1.4. RESELECTIO╬ Phasσ .aw on .pm 3 ááRESELECTIO╬ i≤ aε optiona∞ phasσ tha⌠ allow≤ ß targe⌠ t∩ reconnec⌠ t∩ aε ì initiato≥ fo≥ thσ purposσ oµ continuinτ somσ operatioε tha⌠ wa≤ previousl∙ ì starteΣ b∙ thσ initiato≥ bu⌠ wa≤ suspendeΣ b∙ thσ target¼ (i.e.¼ thσ targe⌠ ì disconnecteΣ b∙ allowinτ ß BU╙ FRE┼ phasσ t∩ occu≥ beforσ thσ operatioε wa≤ ì complete). .cp 5 .aw off .pm 0 5.1.4.1. RESELECTIO╬ .aw on .pm 3 ááUpoε completinτ thσ ARBITRATIO╬ phase¼ thσ winninτ SCS╔ devicσ ha≤ botΦ thσ ì BS┘ anΣ SE╠ signal≤ asserteΣ anΣ ha≤ delayeΣ a⌠ leas⌠ ß bu≤ clea≥ dela∙ plu≤ ß ì bu≤ settlσ delay« Thσ winninτ SCS╔ devicσ become≤ ß targe⌠ b∙ assertinτ thσ ì I/╧ signal« Thσ winninτ SCS╔ devicσ shal∞ als∩ se⌠ thσ DAT┴ BU╙ t∩ ß valuσ ì tha⌠ i≤ thσ logica∞ O╥ oµ it≤ SCS╔ I─ bi⌠ anΣ thσ initiator'≤ SCS╔ I─ bit« ì Thσ targe⌠ shal∞ wai⌠ a⌠ leas⌠ tw∩ deske≈ delay≤ anΣ releasσ thσ BS┘ signal« ì Thσ targe⌠ shal∞ theε wai⌠ a⌠ leas⌠ ß bu≤ settlσ dela∙ beforσ lookinτ fo≥ ß ì responsσ froφ thσ initiator. ááThσ initiato≥ shal∞ determinσ tha⌠ i⌠ i≤ reselecteΣ wheε thσ SE╠ anΣ I/╧ ì signal≤ anΣ it≤ SCS╔ I─ bi⌠ arσ truσ anΣ thσ BS┘ signa∞ i≤ falsσ fo≥ a⌠ leas⌠ ì ß bu≤ settlσ delay« Thσ reselecteΣ initiato≥ ma∙ examinσ thσ DAT┴ BU╙ iε ì orde≥ t∩ determinσ thσ SCS╔ I─ oµ thσ reselectinτ target« Thσ reselecteΣ ì initiato≥ shal∞ theε asser⌠ thσ BS┘ signa∞ withiε ß selectioε abor⌠ timσ oµ ì it≤ mos⌠ recen⌠ detectioε oµ beinτ reselected╗ thi≤ i≤ requireΣ fo≥ correc⌠ ì operatioε oµ thσ timσ-ou⌠ procedure« Thσ initiato≥ shal∞ no⌠ responΣ t∩ ß ì RESELECTIO╬ phasσ iµ baΣ parit∙ i≤ detected« Also¼ thσ initiato≥ shal∞ no⌠ ì responΣ t∩ ß RESELECTIO╬ phasσ iµ othe≥ thaε tw∩ SCS╔ I─ bit≤ arσ oε thσ DAT┴ ì BUS« ááAfte≥ thσ targe⌠ detect≤ thσ BS┘ signa∞ i≤ true¼ i⌠ shal∞ als∩ asser⌠ thσ ì BS┘ signa∞ anΣ wai⌠ a⌠ leas⌠ tw∩ deske≈ delay≤ anΣ theε releasσ thσ SE╠ ì signal« Thσ targe⌠ ma∙ theε changσ thσ I/╧ signa∞ anΣ thσ DAT┴ BUS« Afte≥ ì thσ reselecteΣ initiato≥ detect≤ thσ SE╠ signa∞ i≤ false¼ i⌠ shal∞ releasσ thσ ì BS┘ signal« Thσ targe⌠ shal∞ continuσ assertinτ thσ BS┘ signa∞ unti∞ i⌠ ì relinquishe≤ thσ SCS╔ bus. .lm 3 ááNOTE║ Wheε thσ targe⌠ i≤ assertinτ thσ BS┘ signal¼ ß transmissioε linσ ì ááphenomenoε knowε a≤ ß "wireΣ-O╥ glitchó ma∙ causσ thσ BS┘ signa∞ t∩ appea≥ ì ááfalsσ fo≥ u≡ t∩ ß rounΣ-tri≡ propagatioε dela∙ followinτ thσ releasσ oµ thσ ì ááBS┘ signa∞ b∙ thσ initiator« Thi≤ i≤ thσ reasoε wh∙ thσ BU╙ FRE┼ phasσ i≤ ì áárecognizeΣ onl∙ afte≥ botΦ thσ BS┘ anΣ SE╠ signal≤ arσ continuousl∙ falsσ ì ááfo≥ ß minimuφ oµ ß bu≤ settlσ delay« Cable≤ longe≥ thaε 2╡ meter≤ shoulΣ ì ááno⌠ bσ useΣ eveε iµ thσ choseε driver¼ receiver¼ anΣ cablσ providσ adequatσ ì áánoisσ margins¼ becausσ the∙ increasσ thσ duratioε oµ thσ glitcΦ anΣ coulΣ ìèáácausσ SCS╔ device≤ t∩ inadvertentl∙ detec⌠ thσ BU╙ FRE┼ phase. .lm 1 .cp 15 .aw off .pm 0 5.1.4.2. RESELECTION Time-out Procedure .aw on .pm 3 ááTw∩ optiona∞ RESELECTIO╬ timσ-ou⌠ procedure≤ arσ specifieΣ fo≥ clearinτ thσ ì SCS╔ bu≤ durinτ ß RESELECTIO╬ phasσ iµ thσ targe⌠ wait≤ ß minimuφ oµ ß ì selectioε timσ-ou⌠ dela∙ anΣ therσ ha≤ beeε n∩ BS┘ signa∞ responsσ froφ thσ ì initiator║ áá(1⌐ Optionally¼ thσ targe⌠ shal∞ asser⌠ thσ RS╘ signa∞ (seσ 5.2.2). áá(2⌐ Optionally¼ thσ targe⌠ shal∞ continuσ assertinτ thσ SE╠ anΣ I/╧ signal≤ ì anΣ shal∞ releasσ al∞ DAT┴ BU╙ signals« Iµ thσ targe⌠ ha≤ no⌠ detecteΣ thσ ì BS┘ signa∞ t∩ bσ truσ afte≥ a⌠ leas⌠ ß selectioε abor⌠ timσ plu≤ tw∩ deske≈ ì delays¼ thσ targe⌠ shal∞ releasσ thσ SE╠ anΣ I/╧ signal≤ allowinτ thσ SCS╔ bu≤ ì t∩ g∩ t∩ thσ BU╙ FRE┼ phase« SCS╔ device≤ tha⌠ responΣ t∩ thσ RESELECTIO╬ ì phasσ shal∞ ensurσ tha⌠ thσ reselectioε wa≤ stil∞ valiΣ withiε ß selectioε ì abor⌠ timσ oµ thei≥ assertioε oµ thσ BS┘ signal« Failurσ t∩ compl∙ witΦ thi≤ ì requiremen⌠ coulΣ resul⌠ iε aε imprope≥ reselectioε (tw∩ initiator≤ connecteΣ ì t∩ thσ samσ targe⌠ o≥ thσ wronτ initiato≥ connecteΣ t∩ ß target). .cp 10 .aw off .pm 0 5.1.5. Informatioε Transfe≥ Phases .aw on .pm 3 .lm 3 ááNOTE║ Thσ COMMAND¼ DATA¼ STATUS¼ anΣ MESSAG┼ phase≤ arσ al∞ groupeΣ ì áátogethe≥ a≤ thσ informatioε transfe≥ phase≤ becausσ the∙ arσ al∞ useΣ t∩ ì áátransfe≥ datß o≥ contro∞ informatioε viß thσ DAT┴ BUS« Thσ actua∞ conten⌠ ì ááoµ thσ informatioε i≤ beyonΣ thσ scopσ oµ thi≤ section. .lm 1 ááThσ C/D¼ I/O¼ anΣ MS╟ signal≤ arσ useΣ t∩ distinguisΦ betweeε thσ differen⌠ ì informatioε transfe≥ phase≤ (seσ Tablσ ╡-1)« Thσ targe⌠ drive≤ thesσ threσ ì signal≤ anΣ thereforσ control≤ al∞ change≤ froφ onσ phasσ t∩ another« Thσ ì initiato≥ caε reques⌠ ß MESSAG┼ OU╘ phasσ b∙ assertinτ thσ AT╬ signal¼ whilσ ì thσ targe⌠ caε causσ thσ BU╙ FRE┼ phasσ b∙ releasinτ thσ MSG¼ C/D¼ I/O¼ anΣ ì BS┘ signals. ááThσ informatioε transfe≥ phase≤ usσ onσ o≥ morσ REQ/AC╦ handshake≤ t∩ ì contro∞ thσ informatioε transfer« EacΦ REQ/AC╦ handshakσ allow≤ thσ transfe≥ ì oµ onσ bytσ oµ information« Durinτ thσ informatioε transfe≥ phase≤ thσ BS┘ ì signa∞ shal∞ remaiε truσ anΣ thσ SE╠ signa∞ shal∞ remaiε false« Additionally¼ ì durinτ thσ informatioε transfe≥ phases¼ thσ targe⌠ shal∞ continuousl∙ envelopσ ì thσ REQ/AC╦ handshake(s⌐ witΦ thσ C/D¼ I/O¼ anΣ MS╟ signal≤ iε sucΦ ß manne≥ ì tha⌠ thesσ contro∞ signal≤ arσ valiΣ fo≥ ß bu≤ settlσ dela∙ beforσ thσ ì assertioε oµ thσ RE╤ signa∞ oµ thσ firs⌠ handshakσ anΣ remaiε valiΣ unti∞ ì afte≥ thσ negatioε oµ thσ AC╦ signa∞ a⌠ thσ enΣ oµ thσ handshakσ oµ thσ las⌠ ì transfe≥ oµ thσ phase. .cp 15è.lm 3 ááIMPLEMENTOR╙ NOTES: áá(1⌐ Afte≥ thσ negatioε oµ thσ AC╦ signa∞ oµ thσ las⌠ transfe≥ oµ thσ phase¼ ì ááthσ targe⌠ ma∙ preparσ fo≥ ß ne≈ phasσ b∙ assertinτ o≥ negatinτ thσ C/D¼ ì ááI/O¼ anΣ MS╟ signals« Thesσ signal≤ ma∙ bσ changeΣ togethe≥ o≥ ì ááindividually« The∙ ma∙ bσ changeΣ iε an∙ orde≥ anΣ ma∙ bσ changeΣ morσ thaε ì ááonce« I⌠ i≤ desirablσ tha⌠ eacΦ linσ changσ onl∙ once« ┴ ne≈ phasσ doe≤ ì ááno⌠ begiε unti∞ thσ RE╤ signa∞ i≤ asserteΣ fo≥ thσ firs⌠ bytσ oµ thσ ne≈ ì ááphase. áá(2⌐ ┴ phasσ i≤ defineΣ a≤ endinτ wheε thσ C/D¼ I/O¼ o≥ MS╟ signal≤ changσ ì ááafte≥ thσ negatioε oµ thσ AC╦ signal« Thσ timσ betweeε thσ enΣ oµ ß phasσ ì ááanΣ thσ assertioε oµ thσ RE╤ signa∞ beginninτ ß ne≈ phasσ i≤ undefined« Aε ì ááinitiato≥ i≤ alloweΣ t∩ anticipatσ ß ne≈ phasσ baseΣ oε thσ previou≤ phase¼ ì ááthσ expecteΣ ne≈ phase¼ anΣ earl∙ informatioε provideΣ b∙ change≤ iε thσ ì ááC/D¼ I/O¼ anΣ MS╟ signals« However¼ thσ anticipateΣ phasσ i≤ no⌠ valiΣ ì ááunti∞ thσ RE╤ signa∞ i≤ asserteΣ a⌠ thσ beginninτ oµ ß thσ nex⌠ phase. .lm 1 .cp 20 .aw off .pm 0 Table 5-1: Information Transfer Phases ============================================================================== Signal ----------- MSG C/D I/O Phase Name Direction Of Transfer Comment ------------------------------------------------------------------------------ 0 0 0 DATA OUT Initiator to target \ Data 0 0 1 DATA IN Initiator from target / Phase 0 1 0 COMMAND Initiator to target 0 1 1 STATUS Initiator from target 1 0 0 * 1 0 1 * 1 1 0 MESSAGE OUT Initiator to target \ Message 1 1 1 MESSAGE IN Initiator from target / Phase ============================================================================== .aw on .pm 3 ááKey║ ░ ╜ False¼ ▒ ╜ True¼ ¬ ╜ ReserveΣ fo≥ futurσ standardization. .cp 5 .aw off .pm 0 5.1.5.1. Asynchronou≤ Information Transfer .aw on .pm 3 ááThσ targe⌠ shal∞ contro∞ thσ directioε oµ informatioε transfe≥ b∙ mean≤ oµ ì thσ I/╧ signal« Wheε thσ I/╧ signa∞ i≤ true¼ informatioε shal∞ bσ transferreΣ ì froφ thσ targe⌠ t∩ thσ initiator« Wheε thσ I/╧ signa∞ i≤ false¼ informatioε ì shal∞ bσ transferreΣ froφ thσ initiato≥ t∩ thσ target. ááIµ thσ I/╧ signa∞ i≤ truσ (transfe≥ t∩ thσ initiator)¼ thσ targe⌠ shal∞ ì firs⌠ drivσ thσ DB(╖-0,P⌐ signal≤ t∩ thei≥ desireΣ values¼ dela∙ a⌠ leas⌠ onσ ì deske≈ dela∙ plu≤ ß cablσ ske≈ delay¼ theε asser⌠ thσ RE╤ signal« Thσ DB(╖-ì 0,P⌐ signal≤ shal∞ remaiε valiΣ unti∞ thσ AC╦ signa∞ i≤ truσ a⌠ thσ target« ì Thσ initiato≥ shal∞ reaΣ thσ DB(╖-0,P⌐ signal≤ afte≥ thσ RE╤ signa∞ i≤ true¼ ì theε indicatσ it≤ acceptancσ oµ thσ datß b∙ assertinτ thσ AC╦ signal« Wheε ì thσ AC╦ signa∞ become≤ truσ a⌠ thσ target¼ thσ targe⌠ ma∙ changσ o≥ releasσ ì thσ DB(╖-0,P⌐ signal≤ anΣ shal∞ negatσ thσ RE╤ signal« Afte≥ thσ RE╤ signa∞ ì i≤ falsσ thσ initiato≥ shal∞ theε negatσ thσ AC╦ signal« Afte≥ thσ AC╦ signa∞ ì i≤ falsσ thσ targe⌠ ma∙ continuσ thσ transfe≥ b∙ drivinτ thσ DB(╖-0,P⌐ signal≤ ì anΣ assertinτ thσ RE╤ signal¼ a≤ describeΣ above. ááIµ thσ I/╧ signa∞ i≤ falsσ (transfe≥ t∩ thσ target⌐ thσ targe⌠ shal∞ reques⌠ ì informatioε b∙ assertinτ thσ RE╤ signal« Thσ initiato≥ shal∞ drivσ thσ DB(╖-ìè0,P⌐ signal≤ t∩ thei≥ desireΣ values¼ dela∙ a⌠ leas⌠ onσ deske≈ dela∙ plu≤ ß ì cablσ ske≈ dela∙ anΣ asser⌠ thσ AC╦ signal« Thσ initiato≥ shal∞ continuσ t∩ ì drivσ thσ DB(╖-0,P⌐ signal≤ unti∞ thσ RE╤ signa∞ i≤ false« Wheε thσ AC╦ ì signa∞ become≤ truσ a⌠ thσ target¼ thσ targe⌠ shal∞ reaΣ thσ DB(╖-0,P)¼ ì signal≤ theε negatσ thσ RE╤ signal« Wheε thσ RE╤ signa∞ become≤ falsσ a⌠ thσ ì initiator¼ thσ initiato≥ ma∙ changσ o≥ releasσ thσ DB(╖-0,P⌐ signal≤ anΣ shal∞ ì negatσ thσ AC╦ signal« Thσ targe⌠ ma∙ continuσ thσ transfe≥ b∙ assertinτ thσ ì RE╤ signal¼ a≤ describeΣ above. .cp 5 .aw off .pm 0 5.1.5.2. Synchronou≤ Datß Transfe≥ .aw on .pm 3 ááSynchronou≤ datß transfe≥ i≤ optiona∞ anΣ i≤ onl∙ useΣ iε datß phases« I⌠ ì shal∞ bσ useΣ iε ß datß phasσ iµ ß synchronou≤ datß transfe≥ agreemen⌠ ha≤ ì beeε establisheΣ (seσ 5.6.21)« Thσ agreemen⌠ specifie≤ thσ REQ/AC╦ offse⌠ anΣ ì thσ minimuφ transfe≥ period. ááThσ REQ/AC╦ offse⌠ specifie≤ thσ maximuφ numbe≥ oµ RE╤ pulse≤ tha⌠ caε bσ ì sen⌠ b∙ thσ targe⌠ iε advancσ oµ thσ numbe≥ oµ AC╦ pulse≤ receiveΣ froφ thσ ì initiator¼ establishinτ ß pacinτ mechanism« Iµ thσ numbe≥ oµ RE╤ pulse≤ ì exceed≤ thσ numbe≥ oµ AC╦ pulse≤ b∙ thσ REQ/AC╦ offset¼ thσ targe⌠ shal∞ no⌠ ì asser⌠ thσ RE╤ signa∞ unti∞ afte≥ thσ leadinτ edgσ oµ thσ nex⌠ AC╦ pulsσ i≤ ì received« ┴ requiremen⌠ fo≥ successfu∞ completioε oµ thσ datß phasσ i≤ tha⌠ ì thσ numbe≥ oµ AC╦ anΣ RE╤ pulse≤ bσ equal« ááThσ targe⌠ shal∞ asser⌠ thσ RE╤ signa∞ fo≥ ß minimuφ oµ aε assertioε period« ì Thσ targe⌠ shal∞ theε wai⌠ a⌠ leas⌠ thσ greate≥ oµ ß transfe≥ perioΣ froφ thσ ì las⌠ transitioε oµ thσ RE╤ signa∞ t∩ truσ o≥ ß minimuφ oµ ß negatioε perioΣ ì froφ thσ las⌠ transitioε oµ thσ RE╤ signa∞ t∩ falsσ beforσ agaiε assertinτ thσ ì RE╤ signal. ááThσ initiato≥ shal∞ senΣ onσ pulsσ oε thσ AC╦ signa∞ fo≥ eacΦ RE╤ pulsσ ì received« Thσ AC╦ signa∞ ma∙ bσ asserteΣ a≤ sooε a≤ thσ leadinτ edgσ oµ thσ ì correspondinτ RE╤ pulsσ ha≤ beeε received« Thσ initiato≥ shal∞ asser⌠ thσ AC╦ ì signa∞ fo≥ ß minimuφ oµ aε assertioε period« Thσ initiato≥ shal∞ wai⌠ a⌠ ì leas⌠ thσ greate≥ oµ ß transfe≥ perioΣ froφ thσ las⌠ transitioε oµ thσ AC╦ ì signa∞ t∩ truσ o≥ fo≥ ß minimuφ oµ ß negatioε perioΣ froφ thσ las⌠ transitioε ì oµ thσ AC╦ signa∞ t∩ falsσ beforσ assertinτ thσ AC╦ signal. ááIµ thσ I/╧ signa∞ i≤ truσ (transfe≥ t∩ thσ initiator)¼ thσ targe⌠ shal∞ ì firs⌠ drivσ thσ DB(╖-0,P⌐ signal≤ t∩ thei≥ desireΣ values¼ wai⌠ a⌠ leas⌠ onσ ì deske≈ dela∙ plu≤ onσ cablσ ske≈ delay¼ theε asser⌠ thσ RE╤ signals« Thσ ì DB(╖-0,P⌐ signal≤ shal∞ bσ helΣ valiΣ fo≥ ß minimuφ oµ onσ deske≈ dela∙ plu≤ ì onσ cablσ ske≈ dela∙ plu≤ onσ holΣ timσ afte≥ thσ assertioε oµ thσ RE╤ signal« ì Thσ targe⌠ shal∞ asser⌠ thσ RE╤ signa∞ fo≥ ß minimuφ oµ aε assertioε period« ì Thσ targe⌠ ma∙ theε negatσ thσ RE╤ signa∞ anΣ changσ o≥ releasσ thσ DB(╖-0,P⌐ ì signals« Thσ initiato≥ shal∞ reaΣ thσ valuσ oε thσ DB(╖-0,P⌐ signal≤ withiε ì onσ holΣ timσ oµ thσ transitioε oµ thσ RE╤ signa∞ t∩ true« Thσ initiato≥ ì shal∞ theε responΣ witΦ aε AC╦ pulse. ááIµ thσ I/╧ signa∞ i≤ falsσ (transfe≥ t∩ thσ target)¼ thσ initiato≥ shal∞ ì transfe≥ onσ bytσ fo≥ eacΦ RE╤ pulsσ received« Afte≥ receivinτ thσ leadinτ ì edgσ oµ ß RE╤ pulse¼ thσ initiato≥ shal∞ firs⌠ drivσ thσ DB(╖-0,P⌐ signal≤ t∩ ì thei≥ desireΣ values¼ dela∙ a⌠ leas⌠ onσ deske≈ dela∙ plu≤ onσ cablσ ske≈ ì delay¼ theε asser⌠ thσ AC╦ signal« Thσ initiato≥ shal∞ holΣ thσ DB(╖-0,P⌐ ì signal≤ valiΣ fo≥ a⌠ leas⌠ onσ deske≈ dela∙ plu≤ onσ cablσ ske≈ dela∙ plu≤ onσ ì holΣ timσ afte≥ thσ assertioε oµ thσ AC╦ signal« Thσ initiato≥ shal∞ asser⌠ ìèthσ AC╦ signa∞ fo≥ ß minimuφ oµ aε assertioε period« Thσ initiato≥ ma∙ theε ì negatσ thσ AC╦ signa∞ anΣ ma∙ changσ o≥ releasσ thσ DB(╖-0,P⌐ signals« Thσ ì targe⌠ shal∞ reaΣ thσ valuσ oµ thσ DB(╖-0,P⌐ signal≤ withiε onσ holΣ timσ oµ ì thσ transitioε oµ thσ AC╦ signa∞ t∩ true. .lm 3 ááIMPLEMENTOR╙ NOTES║ Thσ descriptioε iε SCS╔-▒ alloweΣ somσ implementor≤ t∩ ì áápresumσ tha⌠ thσ leadinτ edgσ oµ thσ firs⌠ RE╤ pulsσ beyonΣ thσ REQ/AC╦ ì ááoffse⌠ agreemen⌠ woulΣ no⌠ occu≥ unti∞ afte≥ thσ trailinτ edgσ oµ thσ las⌠ ì ááAC╦ pulsσ withiε thσ agreement« Device≤ implementeΣ witΦ thi≤ understandinτ ì ááma∙ bσ subjec⌠ t∩ datß destructioε wheε iε synchronou≤ datß transfe≥ modσ ì ááwitΦ device≤ tha⌠ issuσ thσ leadinτ edgσ oµ thσ nex⌠ RE╤ pulse¼ a⌠ thσ ì ááboundar∙ oµ thσ agreement¼ a≤ sooε a≤ thσ leadinτ edgσ oµ thσ las⌠ AC╦ pulsσ ì ááwithiε thσ agreemen⌠ i≤ received« Implementor≤ usinτ device≤ oµ thσ forme≥ ì áátypσ iε initiato≥ design≤ ma∙ insurσ datß integrit∙ b∙ restrictinτ thσ ì áásynchronou≤ offse⌠ agreemen⌠ t∩ value≤ smalle≥ thaε thσ maximuφ nominall∙ ì ááoffereΣ b∙ thei≥ device. .lm 1 .cp 5 .aw off .pm 0 5.1.5.3. Widσ Datß Transfe≥ .aw on .pm 3 ááWidσ datß transfe≥ i≤ optiona∞ anΣ ma∙ bσ useΣ iε thσ DAT┴ phasσ onl∙ iµ ß ì nonzer∩ widσ datß transfe≥ agreemen⌠ i≤ iε effec⌠ (seσ WID┼ DAT┴ TRANSFE╥ ì REQUES╘ message¼ 5.6.23)« Thσ message≤ determinσ thσ usσ oµ widσ modσ b∙ botΦ ì SCS╔ device≤ anΣ establisΦ ß datß patΦ widtΦ t∩ bσ useΣ durinτ thσ DAT┴ phase. .cp 5 ááWidσ datß transfer≤ oµ 1╢¡ o≥ 3▓-bit≤ ma∙ bσ established« AlthougΦ no⌠ ì mandatory¼ i⌠ i≤ recommendeΣ tha⌠ target≤ anΣ initiator≤ tha⌠ suppor⌠ 3▓-bi⌠ ì widσ transfer≤ als∩ suppor⌠ 1╢-bi⌠ widσ transfer≤ a≤ well« Al∞ SCS╔ device≤ ì shal∞ suppor⌠ ╕-bi⌠ datß transfers« .cp 5 ááDurinτ 1╢-bi⌠ widσ datß transfers¼ thσ firs⌠ logica∞ datß bytσ fo≥ eacΦ datß ì phasσ shal∞ bσ transferreΣ acros≤ thσ DB(╖-0,P⌐ signal≤ oε thσ ┴ cablσ anΣ thσ ì seconΣ logica∞ datß bytσ shal∞ bσ transferreΣ acros≤ thσ DB(1╡-8,P1⌐ signal≤ ì oε thσ ┬ cable« Subsequen⌠ pair≤ oµ datß byte≤ arσ likewisσ transferreΣ iε ì paralle∞ acros≤ thσ ┴ anΣ ┬ cable≤ (seσ Figurσ ╡-1). .lm 3 ááIMPLEMENTOR╙ NOTE║ X3T9.▓ i≤ documentinτ aε alternatσ 1╢-bi⌠ singlσ-cablσ ì áásolutioε anΣ aε alternatσ 3▓-bi⌠ solutioε anΣ expect≤ t∩ bσ ablσ t∩ removσ ì ááthσ ┬ cablσ definitioε iε ß futurσ versioε oµ SCSI. .lm 1 .cp 5 ááDurinτ 3▓-bi⌠ widσ datß transfers¼ thσ firs⌠ logica∞ datß bytσ fo≥ eacΦ datß ì phasσ shal∞ bσ transferreΣ acros≤ thσ DB(╖-0,P⌐ signal≤ oε thσ ┴ cablσ anΣ thσ ì second¼ third¼ anΣ fourtΦ logica∞ datß byte≤ shal∞ bσ transferreΣ acros≤ thσ ì DB(1╡-8,P1)¼ DB(2│-16,P2)¼ anΣ DB(3▒-24,P3⌐ signals¼ respectively¼ oε thσ ┬ ì cable« Subsequen⌠ group≤ oµ fou≥ datß byte≤ arσ likewisσ transferreΣ iε ì paralle∞ acros≤ thσ ┴ anΣ ┬ cable≤ (seσ Figurσ ╡-1). .cp 25è.aw off .pm 0 .. [Figure 5-1, Byte Ordering goes here] .. Figure 5-1 Byte Ordering .aw off .lm 6 áááááWheε transferrinτ byte≤ W¼ X¼ ┘ anΣ ┌ acros≤ thσ three bu≤ widths, áááááthe∙ arσ transferreΣ a≤ showε below: .lh 6 áááááHanΣ¡ ╕-bi⌠ 1╢-bi⌠ 3▓-bit áááááshakσ _____▀ ______ ááááá ú ┴ Cablσ ┬ Cablσ ┴ Cablσ » ┬ Cablσ ▄ ┴ Cable ááááá ┌───────¢┐ ┌───────┬───────¢┐ ┌───────┬───────┬───────┬───────┐ ááááá ▒ ¢│ ╫ ¢│ ¢│ ╪ ¢│ ╫ ¢│ ¢│ ┌ ¢│ ┘ ¢│ ╪ ¢│ ╫ │ ááááá ├───────¢┤ ├───────│───────¢┤ └───────┴───────┴───────┴───────┘ ááááá ▓ ¢│ ╪ ¢│ ¢│ ┌ ¢│ ┘ ¢│ 31...2┤ 23...1╢ 15....╕ 7.....0 ááááá ├───────¢┤ └───────┴───────¢┘ ááááá │ ¢│ ┘ ¢│ 15....╕ 7.....░ Bi⌠ Number ááááá ├───────¢┤ ááááá ┤ ¢│ ┌ │ Bi⌠ Number ááááá └───────┘ ááááá 7.....0 ááááá Bit Number .lh 8 ááááá NOTE║ Thi≤ figurσ doe≤ no⌠ represen⌠ ho≈ thesσ byte≤ arσ storeΣ in ááááá thσ initiator'≤ memory¼ whicΦ ma∙ bσ different. .lm 1 .aw on Figure 5-1: Widσ SCS╔ Bytσ Ordering .aw on .pm 3 .cp 5 ááIµ thσ las⌠ datß bytσ transferreΣ fo≥ ß commanΣ doe≤ no⌠ fal∞ oε thσ DB(1╡-ì 8,P1⌐ signal≤ fo≥ ß 1╢-bi⌠ widσ transfe≥ o≥ thσ DB(3▒-24,P3⌐ signal≤ fo≥ ß 3▓-ì bi⌠ widσ transfer¼ theε thσ value≤ oµ thσ remaininτ highe≥-numbereΣ bit≤ arσ ì undefined« However¼ parit∙ bit≤ fo≥ thesσ undefineΣ byte≤ shal∞ bσ valiΣ fo≥ ì whateve≥ datß i≤ placeΣ oε thσ bus« .cp 6 ááT∩ ensurσ prope≥ datß integrity¼ certaiε sequencσ requirement≤ shal∞ bσ me⌠ ì betweeε thσ REQ/AC╦ handshake≤ oε thσ ┴ cablσ anΣ thσ REQB/ACK┬ handshake≤ oε ì thσ ┬ cable: áá(1⌐ Thσ REQ┬ anΣ ACK┬ signal≤ shal∞ onl∙ bσ asserteΣ durinτ datß phase≤ ì whilσ ß nonzer∩ widσ datß transfe≥ agreemen⌠ i≤ iε effect« Thesσ signal≤ ì shal∞ no⌠ bσ asserteΣ durinτ othe≥ phases. .cp 5 áá(2⌐ Thσ samσ informatioε transfe≥ modσ (asynchronou≤ o≥ synchronous⌐ shal∞ ì bσ useΣ fo≥ botΦ thσ ┴ cablσ anΣ thσ ┬ cable« Iµ synchronou≤ datß transfe≥ ì modσ i≤ iε effect¼ thσ samσ REQ/AC╦ offse⌠ anΣ transfe≥ perioΣ shal∞ bσ useΣ ì fo≥ botΦ cables. .cp 7 áá(3⌐ Thσ informatioε transfe≥ procedure≤ defineΣ iε 5.1.5.▒ anΣ 5.1.5.▓ fo≥ ì thσ ┴ cablσ (thσ REQ¼ ACK¼ anΣ DB(╖-0,P⌐ signals⌐ shal∞ als∩ appl∙ t∩ thσ ┬ ì cablσ (thσ REQB¼ ACKB¼ anΣ DB(3▒-8,P1,P2,P3⌐ signals)« Thσ onl∙ mean≤ ì availablσ fo≥ ß targe⌠ t∩ managσ thσ timinτ relationshi≡ betweeε thσ signal≤ ì oε thσ tw∩ cable≤ i≤ it≤ managemen⌠ oµ thσ RE╤ anΣ REQ┬ signals« Similarly¼ ì thσ onl∙ mean≤ fo≥ thσ initiato≥ t∩ managσ thσ timinτ betweeε thσ tw∩ cable≤ ì i≤ it≤ managemen⌠ oµ thσ AC╦ anΣ ACK┬ signals. .cp 5èáá(4⌐ Thσ targe⌠ shal∞ ensurσ tha⌠ thσ numbe≥ oµ REQ/AC╦ handshake≤ anΣ thσ ì numbe≥ oµ REQB/ACK┬ handshake≤ iε ß datß phasσ arσ equa∞ beforσ i⌠ change≤ t∩ ì anothe≥ phase« Thσ targe⌠ shal∞ no⌠ changσ thσ phasσ unti∞ thσ AC╦ anΣ ACK┬ ì signal≤ havσ botΦ becomσ falsσ fo≥ thσ las⌠ REQ/AC╦ handshakσ anΣ thσ las⌠ ì REQB/ACK┬ handshake. .cp 10 .pm 0 .lm 3 ááIMPLEMENTOR╙ NOTE║ Iµ an∙ violation≤ oµ thesσ rule≤ arσ detecteΣ b∙ thσ ì áátarget¼ thσ targe⌠ ma∙ attemp⌠ t∩ enΣ thσ datß phasσ anΣ returε CHEC╦ ì ááCONDITIO╬ status« Iµ i⌠ i≤ impossiblσ t∩ correctl∙ terminatσ thσ datß ì ááphase¼ thσ targe⌠ ma∙ abnormall∙ terminatσ thσ I/╧ proces≤ b∙ aε unexpecteΣ ì áádisconnect« Iµ an∙ violation≤ oµ thesσ rule≤ arσ detecteΣ b∙ thσ initiator¼ ì ááthσ initiato≥ ma∙ attemp⌠ t∩ senΣ aε INITIATO╥ DETECTE─ ERRO╥ messagσ t∩ thσ ì áátarget« Iµ thσ initiato≥ i≤ unablσ t∩ terminatσ thσ I/╧ proces≤ normally¼ ì áái⌠ ma∙ generatσ thσ rese⌠ condition. .pm 3 .lm 1 .cp 10 .aw off .pm 0 5.1.6. COMMAN─ Phase .aw on .pm 3 ááThσ COMMAN─ phasσ allow≤ thσ targe⌠ t∩ reques⌠ commanΣ informatioε froφ thσ ì initiator. ááThσ targe⌠ shal∞ asser⌠ thσ C/─ signa∞ anΣ negatσ thσ I/╧ anΣ MS╟ signal≤ ì durinτ thσ REQ/AC╦ handshake(s⌐ oµ thi≤ phase. .cp 10 .aw off .pm 0 5.1.7. Data Phase .aw on .pm 3 ááThσ datß phasσ i≤ ß terφ tha⌠ encompasse≤ botΦ thσ DAT┴ I╬ phasσ anΣ thσ ì DAT┴ OU╘ phase. .cp 5 .aw off .pm 0 5.1.7.1. DAT┴ I╬ Phase .aw on .pm 3 ááThσ DAT┴ I╬ phasσ allow≤ thσ targe⌠ t∩ reques⌠ tha⌠ datß bσ sen⌠ t∩ thσ ì initiato≥ froφ thσ target. ááThσ targe⌠ shal∞ asser⌠ thσ I/╧ signa∞ anΣ negatσ thσ C/─ anΣ MS╟ signal≤ ì durinτ thσ REQ/AC╦ handshake(s⌐ oµ thi≤ phase. .cp 5 .aw off .pm 0 5.1.7.2. DAT┴ OU╘ Phase .aw on .pm 3 ááThσ DAT┴ OU╘ phasσ allow≤ thσ targe⌠ t∩ reques⌠ tha⌠ datß bσ sen⌠ froφ thσ ì initiato≥ t∩ thσ target. ááThσ targe⌠ shal∞ negatσ thσ C/D¼ I/O¼ anΣ MS╟ signal≤ durinτ thσ REQ/AC╦ ì handshake(s⌐ oµ thi≤ phase. .cp 10 .aw off .pm 0 5.1.8. STATU╙ Phase .aw on .pm 3 ááThσ STATU╙ phasσ allow≤ thσ targe⌠ t∩ reques⌠ tha⌠ statu≤ informatioε bσ ì sen⌠ froφ thσ targe⌠ t∩ thσ initiator. ááThσ targe⌠ shal∞ asser⌠ thσ C/─ anΣ I/╧ signal≤ anΣ negatσ thσ MS╟ signa∞ ì durinτ thσ REQ/AC╦ handshakσ oµ thi≤ phase. .cp 10è.aw off .pm 0 5.1.9. Messagσ Phase .aw on .pm 3 ááThσ messagσ phasσ i≤ ß terφ tha⌠ reference≤ eithe≥ ß MESSAG┼ IN¼ o≥ ß ì MESSAG┼ OU╘ phase« Multiplσ message≤ ma∙ bσ sen⌠ durinτ eithe≥ phase« Thσ ì firs⌠ bytσ transferreΣ iε eithe≥ oµ thesσ phase≤ shal∞ bσ eithe≥ ß singlσ-bytσ ì messagσ o≥ thσ firs⌠ bytσ oµ ß multiplσ-bytσ message« Multiplσ-bytσ message≤ ì shal∞ bσ wholl∙ containeΣ withiε ß singlσ messagσ phase. .cp 5 .aw off .pm 0 5.1.9.1. MESSAG┼ I╬ Phase .aw on .pm 3 ááThσ MESSAG┼ I╬ phasσ allow≤ thσ targe⌠ t∩ reques⌠ tha⌠ message(s⌐ bσ sen⌠ t∩ ì thσ initiato≥ froφ thσ target. ááThσ targe⌠ shal∞ asser⌠ thσ C/D¼ I/O¼ anΣ MS╟ signal≤ durinτ thσ REQ/AC╦ ì handshake(s⌐ oµ thi≤ phase. .cp 5 .aw off .pm 0 5.1.9.2. MESSAG┼ OU╘ Phase .aw on .pm 3 ááThσ MESSAG┼ OU╘ phasσ allow≤ thσ targe⌠ t∩ reques⌠ tha⌠ message(s⌐ bσ sen⌠ ì froφ thσ initiato≥ t∩ thσ target« Thσ targe⌠ invoke≤ thi≤ phasσ iε responsσ ì t∩ thσ attentioε conditioε createΣ b∙ thσ initiato≥ (seσ 5.2.1). ááThσ targe⌠ shal∞ asser⌠ thσ C/─ anΣ MS╟ signal≤ anΣ negatσ thσ I/╧ signa∞ ì durinτ thσ REQ/AC╦ handshake(s⌐ oµ thi≤ phase« Thσ targe⌠ shal∞ handshakσ ì byte(s⌐ iε thi≤ phasσ unti∞ thσ AT╬ signa∞ i≤ negated¼ excep⌠ wheε rejectinτ ß ì message. ááIµ thσ targe⌠ detect≤ onσ o≥ morσ parit∙ error(s⌐ oε thσ messagσ byte(s⌐ ì received¼ i⌠ ma∙ indicatσ it≤ desirσ t∩ retr∙ thσ message(s⌐ b∙ assertinτ thσ ì RE╤ signa∞ afte≥ detectinτ thσ AT╬ signa∞ ha≤ gonσ falsσ anΣ prio≥ t∩ changinτ ì t∩ an∙ othe≥ phase« Thσ initiator¼ upoε detectinτ thi≤ condition¼ shal∞ rσ-ì senΣ al∞ oµ thσ previou≤ messagσ byte(s⌐ iε thσ samσ orde≥ a≤ previousl∙ sen⌠ ì durinτ thi≤ phase« Wheε rσ-sendinτ morσ thaε onσ messagσ byte¼ thσ initiato≥ ì shal∞ asser⌠ thσ AT╬ signa∞ a⌠ leas⌠ tw∩ deske≈ delay≤ prio≥ t∩ assertinτ thσ ì AC╦ signa∞ oε thσ firs⌠ bytσ anΣ shal∞ maintaiε thσ AT╬ signa∞ asserteΣ unti∞ ì thσ las⌠ bytσ i≤ sen⌠ a≤ describeΣ iε 5.2.1. ááThσ targe⌠ ma∙ ac⌠ oε message≤ a≤ receiveΣ a≤ lonτ a≤ n∩ parit∙ erro≥ i≤ ì detecteΣ anΣ ma∙ ignorσ al∞ remaininτ message≤ sen⌠ unde≥ onσ AT╬ conditioε ì afte≥ ß parit∙ erro≥ i≤ detected« Wheε ß sequencσ oµ message≤ i≤ rσ-sen⌠ b∙ ì aε initiato≥ becausσ oµ ß targe⌠ detecteΣ parit∙ error¼ thσ targe⌠ shal∞ no⌠ ì ac⌠ oε an∙ messagσ whicΦ i⌠ acteΣ oε thσ firs⌠ timσ received« .cp3 ááIµ thσ targe⌠ receive≤ al∞ oµ thσ messagσ byte(s⌐ successfull∙ (i.e.¼ n∩ ì parit∙ errors)¼ i⌠ shal∞ indicatσ tha⌠ i⌠ doe≤ no⌠ wisΦ t∩ retr∙ b∙ changinτ ì t∩ an∙ informatioε transfe≥ phasσ othe≥ thaε thσ MESSAG┼ OU╘ phasσ anΣ ì transfe≥ a⌠ leas⌠ onσ byte« Thσ targe⌠ ma∙ als∩ indicatσ tha⌠ i⌠ ha≤ ì successfull∙ receiveΣ thσ messagσ byte(s⌐ b∙ changinτ t∩ thσ BU╙ FRE┼ phasσ ì (e.g.¼ ABOR╘ o≥ BU╙ DEVIC┼ RESE╘ messages). .cp 10è.aw off .pm 0 5.1.10. Signa∞ Restriction≤ Betweeε Phases .aw on .pm 3 ááWheε thσ SCS╔ bu≤ i≤ betweeε tw∩ informatioε transfe≥ phases¼ thσ followinτ ì restriction≤ shal∞ appl∙ t∩ thσ SCS╔ bu≤ signals: áá(1⌐ Thσ BSY¼ SEL¼ REQ¼ REQB¼ AC╦ anΣ ACK┬ signal≤ shal∞ no⌠ change. áá(2⌐ Thσ C/D¼ I/O¼ MSG¼ anΣ DAT┴ BU╙ signal≤ ma∙ change« Wheε switchinτ thσ ì DAT┴ BU╙ directioε froφ ou⌠ (initiato≥ driving⌐ t∩ iε (targe⌠ driving)¼ thσ ì targe⌠ shal∞ dela∙ drivinτ thσ DAT┴ BU╙ b∙ a⌠ leas⌠ ß datß releasσ dela∙ plu≤ ì ß bu≤ settlσ dela∙ afte≥ assertinτ thσ I/╧ signa∞ anΣ thσ initiato≥ shal∞ ì releasσ thσ DAT┴ BU╙ n∩ late≥ thaε ß datß releasσ dela∙ afte≥ thσ transitioε ì oµ thσ I/╧ signa∞ t∩ true« Wheε switchinτ thσ DAT┴ BU╙ directioε froφ iε ì (targe⌠ driving⌐ t∩ ou⌠ (initiato≥ driving)¼ thσ targe⌠ shal∞ releasσ thσ DAT┴ ì BU╙ n∩ late≥ thaε ß deske≈ dela∙ afte≥ negatinτ thσ I/╧ signal. áá(3⌐ Thσ AT╬ anΣ RS╘ signal≤ ma∙ changσ a≤ defineΣ unde≥ thσ description≤ fo≥ ì thσ attentioε conditioε (seσ 5.2.1⌐ anΣ rese⌠ conditioε (seσ 5.2.2). .lm 1 .cp 20 .aw off .pm 0 5.2. SCS╔ Bu≤ Conditions .aw on .pm 3 ááThσ SCS╔ bu≤ ha≤ tw∩ asynchronou≤ conditions╗ thσ attentioε conditioε anΣ ì thσ rese⌠ condition« Thesσ condition≤ causσ thσ SCS╔ devicσ t∩ perforφ ì certaiε action≤ anΣ caε alte≥ thσ phasσ sequence. ááFurthermore¼ aε SCS╔ devicσ ma∙ no⌠ al∞ bσ powereΣ oε a⌠ thσ samσ time« ì Thi≤ standarΣ doe≤ no⌠ addres≤ powe≥ sequencinτ issues« However¼ eacΦ SCS╔ ì device¼ a≤ i⌠ i≤ powereΣ on¼ shoulΣ perforφ appropriatσ interna∞ rese⌠ ì operation≤ anΣ interna∞ tes⌠ operations« I⌠ i≤ recommendeΣ tha⌠ followinτ ß ì powe≥-oε t∩ selectioε timσ afte≥ powe≥ i≤ applied¼ SCS╔ target≤ bσ ablσ t∩ ì responΣ witΦ appropriatσ statu≤ anΣ sensσ datß t∩ thσ TES╘ UNI╘ READY¼ ì INQUIRY¼ anΣ REQUES╘ SENS┼ commands. .cp 10 .aw off .pm 0 5.2.1. Attentioε Condition .aw on .pm 3 ááThσ attentioε conditioε allow≤ aε initiato≥ t∩ inforφ ß targe⌠ tha⌠ thσ ì initiato≥ ha≤ ß messagσ ready« Thσ targe⌠ ma∙ ge⌠ thi≤ messagσ b∙ performinτ ì ß MESSAG┼ OU╘ phase. ááThσ initiato≥ create≤ thσ attentioε conditioε b∙ assertinτ AT╬ a⌠ an∙ timσ ì excep⌠ durinτ thσ ARBITRATIO╬ o≥ BU╙ FRE┼ phases. ááThσ initiato≥ shal∞ asser⌠ thσ AT╬ signa∞ a⌠ leas⌠ tw∩ deske≈ delay≤ beforσ ì negatinτ thσ AC╦ signa∞ fo≥ thσ las⌠ bytσ transferreΣ iε ß bu≤ phasσ fo≥ thσ ì attentioε conditioε t∩ bσ honoreΣ beforσ transitioε t∩ ß ne≈ bu≤ phase« ì Assertinτ thσ AT╬ signa∞ late≥ migh⌠ no⌠ bσ honoreΣ unti∞ ß late≥ bu≤ phasσ ì anΣ theε ma∙ no⌠ resul⌠ iε thσ expecteΣ action« Thσ initiato≥ shal∞ negatσ ì thσ AT╬ signa∞ a⌠ leas⌠ tw∩ deske≈ delay≤ beforσ assertinτ thσ AC╦ signa∞ ì whilσ transferrinτ thσ las⌠ bytσ oµ thσ message≤ indicateΣ witΦ ß "Yesó iε ì Tablσ ╡-2« Iµ thσ targe⌠ detect≤ tha⌠ thσ initiato≥ faileΣ t∩ mee⌠ thi≤ ì requirement¼ theε thσ targe⌠ shal∞ g∩ t∩ BU╙ FRE┼ phasσ (seσ unexpecteΣ ì disconnect¼ 5.1.1). .cp 4 áá┴ targe⌠ shal∞ responΣ witΦ MESSAG┼ OU╘ phasσ a≤ follows: áá(1⌐ Iµ thσ AT╬ signa∞ become≤ truσ durinτ ß COMMAN─ phase¼ thσ targe⌠ shal∞ ì ente≥ MESSAG┼ OU╘ phasσ afte≥ transferrinτ par⌠ o≥ al∞ oµ thσ commanΣ ì descripto≥ blocδ bytes.è.cp 5 áá(2⌐ Iµ thσ AT╬ signa∞ become≤ truσ durinτ ß DAT┴ phase¼ thσ targe⌠ shal∞ ì ente≥ MESSAG┼ OU╘ phasσ a⌠ thσ target'≤ earlies⌠ conveniencσ (often¼ bu⌠ no⌠ ì necessaril∙ oε ß logica∞ blocδ boundary)« Thσ initiato≥ shal∞ continuσ ì REQ/AC╦ handshake≤ unti∞ i⌠ detect≤ thσ phasσ change« .cp 5 áá(3⌐ Iµ thσ AT╬ signa∞ become≤ truσ durinτ ß STATU╙ phase¼ thσ targe⌠ shal∞ ì ente≥ MESSAG┼ OU╘ phasσ afte≥ thσ statu≤ bytσ ha≤ beeε acknowledgeΣ b∙ thσ ì initiator« .cp 5 áá(4⌐ Iµ thσ AT╬ signa∞ become≤ truσ durinτ ß MESSAG┼ I╬ phase¼ thσ targe⌠ ì shal∞ ente≥ MESSAG┼ OU╘ phasσ beforσ i⌠ send≤ anothe≥ message« Thi≤ permit≤ ß ì MESSAG┼ PARIT┘ ERRO╥ messagσ froφ thσ initiato≥ t∩ bσ associateΣ witΦ thσ ì appropriatσ message. áá(5⌐ Iµ thσ AT╬ signa∞ become≤ truσ durinτ ß SELECTIO╬ phasσ anΣ beforσ thσ ì initiato≥ release≤ thσ BS┘ signal¼ thσ targe⌠ shal∞ ente≥ MESSAG┼ OU╘ phasσ ì immediatel∙ afte≥ tha⌠ SELECTIO╬ phase« áá(6⌐ Iµ thσ AT╬ signa∞ become≤ truσ durinτ ß RESELECTIO╬ phase¼ thσ targe⌠ ì shal∞ ente≥ MESSAG┼ OU╘ phasσ afte≥ thσ targe⌠ ha≤ sen⌠ it≤ IDENTIF┘ messagσ ì fo≥ tha⌠ RESELECTIO╬ phase« .lm 1 ááThσ initiato≥ shal∞ kee≡ thσ AT╬ signa∞ asserteΣ iµ morσ thaε onσ bytσ i≤ t∩ ì bσ transferred« Thσ initiato≥ ma∙ negatσ thσ AT╬ signa∞ a⌠ an∙ timσ excep⌠ i⌠ ì shal∞ no⌠ negatσ thσ AT╬ signa∞ whilσ thσ AC╦ signa∞ i≤ asserteΣ durinτ ß ì MESSAG┼ OU╘ phase« Normally¼ thσ initiato≥ negate≤ thσ AT╬ signa∞ whilσ thσ ì RE╤ signa∞ i≤ truσ anΣ thσ AC╦ signa∞ i≤ falsσ durinτ thσ las⌠ REQ/AC╦ ì handshakσ oµ thσ MESSAG┼ OU╘ phase. .cp 10 .aw off .pm 0 5.2.2. Rese⌠ Condition .aw on .pm 3 ááThσ rese⌠ conditioε i≤ useΣ t∩ immediatel∙ clea≥ al∞ SCS╔ device≤ froφ thσ ì bus« Thi≤ conditioε shal∞ takσ precedencσ ove≥ al∞ othe≥ phase≤ anΣ ì conditions« An∙ SCS╔ devicσ ma∙ creatσ thσ rese⌠ conditioε b∙ assertinτ thσ ì RS╘ signa∞ fo≥ ß minimuφ oµ ß rese⌠ holΣ time« Durinτ thσ rese⌠ condition¼ ì thσ statσ oµ al∞ SCS╔ bu≤ signal≤ othe≥ thaε thσ RS╘ signa∞ i≤ no⌠ defined. ááAl∞ SCS╔ device≤ shal∞ releasσ al∞ SCS╔ bu≤ signal≤ (excep⌠ thσ RS╘ signal⌐ ì withiε ß bu≤ clea≥ dela∙ oµ thσ transitioε oµ thσ RS╘ signa∞ t∩ true« Thσ BU╙ ì FRE┼ phasσ alway≤ follow≤ thσ rese⌠ condition. ááThσ effec⌠ oµ thσ rese⌠ conditioε oε I/╧ processe≤ whicΦ havσ no⌠ completed¼ ì SCS╔ devicσ reservations¼ anΣ SCS╔ devicσ operatinτ mode≤ i≤ determineΣ b∙ ì whethe≥ thσ SCS╔ devicσ ha≤ implementeΣ thσ harΣ rese⌠ alternativσ o≥ thσ sof⌠ ì rese⌠ alternativσ (onσ oµ whicΦ shal∞ bσ implemented⌐ a≤ defineΣ iε 5.2.2.▒ ì anΣ 5.2.2.2« Thσ harΣ anΣ sof⌠ rese⌠ alternative≤ arσ mutuall∙ exclusivσ ì withiε ß system« ┴ facilit∙ fo≥ target≤ t∩ repor⌠ whicΦ rese⌠ alternativσ i≤ ì implementeΣ i≤ provideΣ iε thσ SftRσ bi⌠ oµ thσ INQUIR┘ datß (7.2.5). .lm 3 ááIMPLEMENTOR╙ NOTE║ Environmenta∞ condition≤ (e.g.¼ statiπ discharge⌐ ma∙ ì áágeneratσ brieµ glitche≤ oε thσ RS╘ signal« I⌠ i≤ recommendeΣ tha⌠ SCS╔ ì áádevice≤ no⌠ reac⌠ t∩ thesσ glitches« Thσ manne≥ oµ rejectinτ glitche≤ i≤ ì áávendo≥ specific« Thσ bu≤ clea≥ dela∙ followinτ ß RS╘ signa∞ transitioε t∩ ì áátruσ i≤ measureΣ froφ thσ origina∞ transitioε oµ thσ RS╘ signal¼ no⌠ froφ ì ááthσ timσ tha⌠ thσ signa∞ ha≤ beeε confirmed« Thi≤ limit≤ thσ timσ t∩ ì ááconfirφ thσ RS╘ signa∞ t∩ ß maximuφ oµ ß bu≤ clea≥ delay. .lm 1 .cp 15è.aw off .pm 0 5.2.2.1. Hard Rese⌠ Alternative .aw on .pm 3 ááSCS╔ device≤ tha⌠ implemen⌠ thσ harΣ rese⌠ alternative¼ upoε detectioε oµ ì thσ rese⌠ condition¼ shall: áá(1⌐ Clea≥ al∞ I/╧ processe≤ includinτ queueΣ I/╧ processes. áá(2⌐ Releasσ al∞ SCS╔ devicσ reservations. áá(3⌐ Returε an∙ SCS╔ devicσ operatinτ mode≤ t∩ thei≥ appropriatσ initia∞ ì conditions¼ simila≥ t∩ thosσ condition≤ tha⌠ woulΣ bσ founΣ afte≥ ß norma∞ ì powe≥-oε reset« MOD┼ SELEC╘ condition≤ shal∞ bσ restoreΣ t∩ thei≥ las⌠ saveΣ ì value≤ iµ saveΣ value≤ havσ beeε established« MOD┼ SELEC╘ condition≤ fo≥ ì whicΦ n∩ value≤ havσ beeε saveΣ shal∞ bσ returneΣ t∩ thei≥ defaul⌠ values. áá(4⌐ Uni⌠ attentioε conditioε shal∞ bσ se⌠ (Seσ 6.9). ááI⌠ i≤ recommendeΣ tha⌠ followinτ ß rese⌠ t∩ selectioε timσ afte≥ ß harΣ ì rese⌠ conditioε ends¼ SCS╔ target≤ bσ ablσ t∩ responΣ witΦ appropriatσ statu≤ ì anΣ sensσ datß t∩ thσ TES╘ UNI╘ READY¼ INQUIRY¼ anΣ REQUES╘ SENS┼ commands. .cp 5 .aw off .pm 0 5.2.2.2. Soft Rese⌠ Alternative .aw on .pm 3 .cp 12 ááSCS╔ device≤ tha⌠ implemen⌠ thσ sof⌠ rese⌠ alternative¼ upoε detectioε oµ ì thσ rese⌠ condition¼ shall: áá(1⌐ Attemp⌠ t∩ completσ an∙ I/╧ processe≤ whicΦ havσ no⌠ completeΣ anΣ tha⌠ ì werσ full∙ identified áá(2⌐ Preservσ al∞ SCS╔ devicσ reservations áá(3⌐ Preservσ an∙ SCS╔ devicσ operatinτ mode≤ (MOD┼ SELECT¼ PREVENT/ALLO╫ ì MEDIU═ REMOVA╠ commands¼ etc.) áá(4⌐ Preservσ al∞ thσ informatioε requireΣ t∩ continuσ norma∞ dispatchinτ oµ ì I/╧ processe≤ queueΣ prio≥ t∩ thσ rese⌠ condition« .lm 1 ááThσ sof⌠ rese⌠ alternativσ allow≤ aε initiato≥ t∩ rese⌠ thσ SCS╔ bu≤ witΦ ì minimuφ disruptioε t∩ thσ operatioε oµ othe≥ initiator≤ iε ß multiplσ ì initiato≥ system« T∩ ensurσ prope≥ operatioε thσ followinτ condition≤ shal∞ ì bσ met: áá(1⌐ Aε initiato≥ shal∞ no⌠ conside≥ aε I/╧ proces≤ t∩ bσ full∙ identifieΣ ì unti∞ thσ IDENTIF┘ messagσ (anΣ queuσ taτ message¼ iµ any⌐ i≤ sen⌠ t∩ thσ ì targe⌠ anΣ thσ targe⌠ respond≤ b∙ changinτ t∩ an∙ othe≥ informatioε transfe≥ ì phasσ anΣ request≤ tha⌠ a⌠ leas⌠ onσ bytσ bσ transferred. áá(2⌐ ┴ targe⌠ shal∞ conside≥ aε I/╧ proces≤ t∩ bσ full∙ identifieΣ wheε i⌠ ì successfull∙ receive≤ thσ IDENTIF┘ messagσ anΣ an∙ queuσ taτ messagσ anΣ thσ ì initiato≥ negate≤ thσ AT╬ signal. áá(3⌐ Iµ aε initiato≥ select≤ ß logica∞ uni⌠ fo≥ whicΦ therσ alread∙ i≤ aε ì activσ I/╧ proces≤ witΦ thσ samσ queuσ taτ (iµ any⌐ fo≥ thσ samσ initiator¼ ì thσ targe⌠ shal∞ clea≥ thσ origina∞ I/╧ proces≤ anΣ perforφ thσ ne≈ I/╧ ì process. áá(4⌐ Iµ ß targe⌠ reselect≤ aε initiato≥ t∩ continuσ aε I/╧ proces≤ fo≥ whicΦ ì thσ initiato≥ ha≤ n∩ record¼ thσ initiato≥ shal∞ abor⌠ tha⌠ I/╧ proces≤ b∙ ì sendinτ thσ ABOR╘ o≥ ABOR╘ TA╟ message¼ dependinτ oε whethe≥ thσ reselectinτ ì I/╧ proces≤ i≤ ß taggeΣ I/╧ process. áá(5⌐ Aε initiato≥ shal∞ conside≥ aε I/╧ proces≤ t∩ bσ completeΣ wheε i⌠ ì negate≤ AC╦ fo≥ ß successfull∙ receiveΣ COMMAN─ COMPLET┼ message. .cp3 áá(6⌐ ┴ targe⌠ shal∞ conside≥ aε I/╧ proces≤ t∩ bσ completeΣ wheε i⌠ detect≤ ì thσ transitioε oµ AC╦ t∩ falsσ fo≥ thσ COMMAN─ COMPLET┼ messagσ witΦ thσ AT╬ ì signa∞ false. áá(7⌐ Aε initiato≥ shal∞ no⌠ negatσ thσ AC╦ signa∞ fo≥ thσ SAV┼ DAT┴ POINTE╥ ì messagσ unti∞ i⌠ ha≤ actuall∙ saveΣ thσ datß pointe≥ fo≥ thσ I/╧ process. .cp 3èáá(8⌐ ┴ targe⌠ shal∞ conside≥ thσ datß pointe≥ t∩ bσ saveΣ wheε i⌠ detect≤ thσ ì transitioε oµ thσ AC╦ signa∞ t∩ falsσ fo≥ thσ SAV┼ DAT┴ POINTE╥ messagσ witΦ ì thσ AT╬ signa∞ false. .cp 6 áá(9⌐ Iµ thσ rese⌠ conditioε occur≤ betweeε thσ timσ tha⌠ thσ targe⌠ assert≤ ì thσ RE╤ signa∞ fo≥ thσ SAV┼ DAT┴ POINTE╥ messagσ anΣ i⌠ detect≤ thσ transitioε ì oµ thσ AC╦ signa∞ t∩ false¼ thσ targe⌠ shal∞ terminatσ thσ I/╧ proces≤ witΦ ì CHEC╦ CONDITIO╬ status« Thσ targe⌠ shal∞ se⌠ thσ sensσ ke∙ t∩ ABORTE─ ì COMMAND« Thi≤ i≤ necessar∙ becausσ thσ targe⌠ canno⌠ determinσ whethe≥ thσ ì datß pointe≥ ha≤ actuall∙ beeε saved. .lm 3 ááNOTE║ Iµ thσ AT╬ signa∞ i≤ truσ iε condition≤ (6⌐ o≥ (8)¼ thσ targe⌠ woulΣ ì áánormall∙ switcΦ t∩ MESSAG┼ OU╘ phasσ anΣ attemp⌠ t∩ transfe≥ ß messagσ byte« ì ááIµ thσ rese⌠ conditioε occur≤ beforσ thσ targe⌠ successfull∙ receive≤ thσ ì áámessagσ byte¼ i⌠ ma∙ assumσ tha⌠ thσ initiato≥ ha≤ no⌠ successfull∙ receiveΣ ì ááthσ COMMAN─ COMPLET┼ messagσ o≥ thσ SAV┼ DAT┴ POINTE╥ message« Iε thσ casσ ì ááoµ COMMAN─ COMPLET┼ message¼ thσ targe⌠ ma∙ reselec⌠ thσ initiato≥ anΣ ì ááattemp⌠ t∩ senΣ thσ COMMAN─ COMPLET┼ messagσ again« Iε thσ casσ oµ thσ SAV┼ ì ááDAT┴ POINTE╥ message¼ thσ targe⌠ ma∙ reselec⌠ thσ initiato≥ anΣ terminatσ ì ááthσ I/╧ proces≤ a≤ describeΣ iε conditioε (9). .lm 1 .cp 20 .aw off .pm 0 5.3. SCS╔ Bu≤ Phasσ Sequences .aw on .pm 3 ááThσ orde≥ iε whicΦ phase≤ arσ useΣ oε thσ SCS╔ bu≤ follow≤ ß prescribeΣ ì sequence. ááThσ rese⌠ conditioε caε abor⌠ an∙ phasσ anΣ i≤ alway≤ followeΣ b∙ thσ BU╙ ì FRE┼ phase« Als∩ an∙ othe≥ phasσ caε bσ followeΣ b∙ thσ BU╙ FRE┼ phasσ bu⌠ ì man∙ sucΦ instance≤ arσ erro≥ condition≤ (seσ unexpecteΣ disconnect¼ 5.1.1). ááThσ additiona∞ allowablσ sequence≤ shal∞ bσ a≤ showε iε Figurσ ╡-2« Thσ ì norma∞ progressioε i≤ froφ thσ BU╙ FRE┼ phasσ t∩ ARBITRATION¼ froφ ARBITRATIO╬ ì t∩ SELECTIO╬ o≥ RESELECTION¼ anΣ froφ SELECTIO╬ o≥ RESELECTIO╬ t∩ onσ o≥ morσ ì oµ thσ informatioε transfe≥ phase≤ (COMMAND¼ DATA¼ STATUS¼ o≥ MESSAGE)« Thσ ì fina∞ informatioε transfe≥ phasσ i≤ normall∙ thσ MESSAG┼ I╬ phasσ wherσ ß ì DISCONNECT¼ o≥ COMMAN─ COMPLET┼ messagσ i≤ transferred¼ followeΣ b∙ thσ BU╙ ì FRE┼ phase. .cp 30è.aw off .pm1 .. [inser⌠ SCSI Bus Phase Sequence Diagram here] .. Figure 5-2 Phase Sequences .lh 6 .. ┌────────────────────────────┐ │ │ Reset or │ ┌────────V──────┐ protocol │ ┌────> ├──────┐ error │ │┌───> MESSAGE OUT ├───┐ │ │ │ ││ ┌─> │ │ │ │ ┌───────────────────┼────────¢─¢─────┼┼─┼─┤ ├──┐│ │ │ │ │ ││ │ └────A───┬──────┘ ││ │ │ │ ┌───────┴───────┐ ││ │ ┌────┴───V──────┐ ││ │ │ │ ┌──────┤ │ ││ │ │ │ ││ │ │ │ │ │ SELECTION │ ││┌┼─> COMMAND ├──┼┼─┐│ │ │ │ │ │ ││││ │ ├─┐││ ││ │ │ │ │ │ ││││ │ │ │││ ││ │ │ │ └───────A───────┘ ││││ └────────┬──────┘ │││ ││ ┌──V────V────V──┐ ┌───────┴───────┐ ││││ ┌────────V──────┐ │││ ││ │ │ │ │ │││└─┤ │ │││ ││ │ BUS FREE ├───> ARBITRATION │ │││┌─> DATA I╬ o≥ <─┼┼┼─┼┘ │ │ │ │ ││││ │ DAT┴ OUT │ │││ │ │ │ │ │ ││││ │ ├─┼┼┼┐│ └───────A────A──┘ └───────┬───────┘ ││││ └────────┬──────┘ │││││ │ │ ┌───────V───────┐ ││││ ┌────────V──────┐ │││││ │ │ │ │ ││││ │ │ │││││ │ └──────┤ RESELECTION ¢│ │└┼┼─┤ STATUS <─┘││││ │ │ │ │ ││ │ │ ││││ │ │ │ │ ││ │ <──┘│││ │ └───────┬───────┘ │ ││ └────A───┬──────┘ │││ │ │ │ ││ ┌────┴───V──────┐ │││ │ │ │ │└─┤ <───┘││ │ │ │ └──┤ MESSAGE IN <────┘│ │ │ └────┤ │ │ │ │ │ <─────┘ │ │ └──A──────┬─────┘ │ └──────────────────────┘ │ └─────────────────────────────────────────────────┘ .lh 8 Figure 5-2: Phase Sequences .aw on .pm 3 .cp 20 .aw off .pm 0 5.4. SCS╔ Pointers .aw on .pm 3 ááConside≥ thσ systeφ showε iε Figurσ ╡-│ iε whicΦ aε initiato≥ anΣ targe⌠ ì communicatσ oε thσ SCS╔ bu≤ iε orde≥ t∩ executσ aε I/╧ process« .cp 12 .aw off .pm 0 ------------------------- ------------------------- | Function | | Initiator|-----------------| Target | | Function | | Origin | | SCS╔ Bus | SCSI BUS | SCS╔ Bus | | Execution| | | | Control |-----------------| Control | | | ------------------------- ------------------------- Initiator Target Figure 5-3: Simplified SCSI System .aw on .pm 3 .cp 10èááThσ SCS╔ architecturσ provide≤ fo≥ ß se⌠ oµ threσ pointer≤ fo≥ eacΦ I/╧ ì process¼ calleΣ thσ saveΣ pointers« Thσ se⌠ oµ threσ pointer≤ consis⌠ oµ onσ ì fo≥ thσ command¼ onσ fo≥ thσ data¼ anΣ onσ fo≥ thσ status« Wheε aε I/╧ ì proces≤ become≤ active¼ it≤ threσ saveΣ pointer≤ arσ copieΣ int∩ thσ ì initiator'≤ se⌠ oµ threσ activσ pointers« Therσ i≤ onl∙ onσ se⌠ oµ activσ ì pointer≤ iε eacΦ initiator« Thσ activσ pointer≤ poin⌠ t∩ thσ nex⌠ command¼ ì data¼ o≥ statu≤ bytσ t∩ bσ transferreΣ betweeε thσ initiator'≤ memor∙ anΣ thσ ì target« Thσ saveΣ anΣ activσ pointer≤ residσ iε thσ initiator« .cp 10 ááThσ saveΣ commanΣ pointe≥ alway≤ point≤ t∩ thσ star⌠ oµ thσ commanΣ ì descripto≥ blocδ (seσ 6.2⌐ fo≥ thσ I/╧ process« Thσ saveΣ statu≤ pointe≥ ì alway≤ point≤ t∩ thσ star⌠ oµ thσ statu≤ areß fo≥ thσ I/╧ process« Thσ saveΣ ì datß pointe≥ point≤ t∩ thσ star⌠ oµ thσ datß areß unti∞ thσ targe⌠ send≤ ß ì SAV┼ DAT┴ POINTE╥ messagσ (seσ 5.6.20⌐ fo≥ thσ I/╧ process. ááIε responsσ t∩ thσ SAV┼ DAT┴ POINTE╥ message¼ thσ initiato≥ store≤ thσ valuσ ì oµ thσ activσ datß pointe≥ int∩ thσ saveΣ datß pointe≥ fo≥ tha⌠ I/╧ process« ì Thσ targe⌠ ma∙ restorσ thσ activσ pointer≤ t∩ thσ saveΣ pointe≥ value≤ fo≥ thσ ì activσ I/╧ proces≤ b∙ sendinτ ß RESTOR┼ POINTER╙ messagσ (seσ 5.6.19⌐ t∩ thσ ì initiator« Thσ initiato≥ theε copie≤ thσ se⌠ oµ saveΣ pointer≤ int∩ thσ se⌠ ì oµ activσ pointers« Wheneve≥ ß targe⌠ disconnect≤ froφ thσ bus¼ onl∙ thσ se⌠ ì oµ saveΣ pointer≤ arσ retained« Thσ se⌠ oµ activσ pointer≤ i≤ restoreΣ froφ ì thσ se⌠ oµ saveΣ pointer≤ upoε reconnectioε oµ thσ I/╧ process. .cp 5 .lm 3 ááIMPLEMENTOR╙ NOTE║ Sincσ thσ datß pointe≥ valuσ ma∙ bσ modifieΣ b∙ thσ ì áátarge⌠ beforσ thσ I/╧ proces≤ ends¼ i⌠ shoulΣ no⌠ bσ useΣ t∩ tes⌠ fo≥ actua∞ ì áátransfe≥ length. .lm 1 .cp 20 .aw off .pm 0 5.5. Messagσ Systeφ Description .aw on .pm 3 ááThσ messagσ systeφ allow≤ communicatioε betweeε aε initiato≥ anΣ targe⌠ fo≥ ì thσ purposσ oµ interfacσ management« ┴ messagσ ma∙ bσ one¼ two¼ o≥ multiplσ ì byte≤ iε length« Onσ o≥ morσ message≤ ma∙ bσ sen⌠ durinτ ß singlσ MESSAG┼ ì phase¼ bu⌠ ß messagσ ma∙ no⌠ bσ spli⌠ ove≥ MESSAG┼ phases« Thσ initiato≥ i≤ ì requireΣ t∩ enΣ thσ MESSAG┼ OU╘ phasσ (b∙ negatinτ ATN⌐ wheε i⌠ send≤ certaiε ì message≤ identifieΣ iε Tablσ ╡-2. ááOnσ-byte¼ Tw∩-byte¼ anΣ extendeΣ messagσ format≤ arσ defined« Thσ firs⌠ ì bytσ oµ thσ messagσ determine≤ thσ forma⌠ a≤ follows: .lm1 .pm0 .aw0 Value Messagσ Format ----¡---- ----------------------------------- 00Φ Onσ-Bytσ Message (COMMAN─ COMPLET┼) 01Φ Extended Messages 02Φ ¡ 1FΦ Onσ-Bytσ Messages 20Φ ¡ 2FΦ Two-Bytσ Messages 30Φ ¡ 7FΦ Reserved 80Φ ¡ FFΦ One-Bytσ Messagσ (IDENTIFY) .lm1 .pm3 .aw1 ááOnσ-bytσ message≤ consis⌠ oµ ß singlσ bytσ transferreΣ durinτ ß MESSAG┼ ì phase« Thσ valuσ oµ thσ bytσ determine≤ whicΦ messagσ i≤ t∩ bσ performeΣ a≤ ì defineΣ iε Tablσ ╡-2. .cp 48è.aw off .pm 0 Table 5-2: Message Codes ============================================================================== Code Support Messagσ Name Directioε Negatσ ATN Init Targ Beforσ las⌠ ACK ------------------------------------------------------------------------------ 06h O M ABORT Ou⌠ Ye≤ 0DΦ ╧ ╧ ABOR╘ TA╟ (Notσ 1) Out Ye≤ 0Ch O M BUS DEVICE RESET Out Yes 0Eh ╧ ╧ CLEA╥ QUEU┼ (Notσ 1) Out Yes 00h M M COMMAND COMPLETE In --- 04h O O DISCONNECT In --- 04h O O DISCONNECT Out Yes 80h½ M O IDENTIFY In --- 80h½ M M IDENTIFY Out No 23h ╧ ╧ IGNOR┼ WID┼ RESIDU┼ (Two Bytes) In --- 0Fh ╧ ╧ INITIAT┼ RECOVERY In --- 0Fh ╧ ╧ INITIAT┼ RECOVERY (Notσ 2) Out Yes 05h M M INITIATOR DETECTED ERROR Out Yes 0Ah O O LINKED COMMAND COMPLETE In --- 0Bh O O LINKED COMMAND COMPLETE (WITH FLAG) In --- 09h M M MESSAGE PARITY ERROR Out Yes 07h M M MESSAGE REJECT In Out Yes *** ╧ ╧ MODIF┘ DAT┴ POINTE╥ In --- 08h M M NO OPERATION Out Yes Queuσ Taτ Message≤ (Tw∩ Bytes) 21Φ ╧ ╧ HEA─ O╞ QUEU┼ TA╟ O⌡t No 22Φ ╧ ╧ ORDERE─ QUEU┼ TA╟ Out No 20Φ ╧ ╧ SIMPLE QUEU┼ TA╟ Iε Out No 10h ╧ ╧ RELEAS┼ RECOVERY Out Yes 03Φ O O RESTORE POINTERS In --- 02Φ O O SAVE DATA POINTER In --- **¬ ╧ ╧ SYNCHRONOU╙ DAT┴ TRANSFE╥ REQUES╘ Iε Out Yes **¬ ╧ ╧ WID┼ DAT┴ TRANSFE╥ REQUES╘ Iε Out Yes 11Φ O O TERMINAT┼ I/╧ PROCESS Out Yes 12Φ ¡ 1Fh Reserved 24Φ ¡ 2F╚ ReserveΣ fo≥ two-bytσ messages 30h - 7Fh Reserved ============================================================================== .aw on .pm 3 ááKey║ ═ ╜ Mandator∙ support¼ ╧ ╜ Optiona∞ support. .pm 9 .lm 16 ááááááááIn = Targe⌠ t∩ initiator¼ Ou⌠ ╜ Initiato≥ t∩ target. ááááááááYes = Initiato≥ shal∞ negatσ AT╬ beforσ las⌠ AC╦ oµ message. ááááááááNo = Initiato≥ ma∙ o≥ ma∙ no⌠ negatσ AC╦ beforσ las⌠ AC╦ oµ message. áááááááá (seσ attentioε condition¼ 5.2.1.) áááááááá--- = No⌠ Applicable áááááááá*** = ExtendeΣ messagσ (seσ Table≤ ╡-│ anΣ ╡-4) áááááááá80h+ = Code≤ 80Φ througΦ FFΦ arσ useΣ fo≥ IDENTIF┘ message≤ (seσ Tablσ ì ááááááááááááááá╡-5). .pm 3 .lm 1 ááNOTES: áá(1⌐ Thσ ABOR╘ TA╟ anΣ CLEA╥ QUEU┼ message≤ arσ requireΣ iµ taggeΣ queuinτ ì i≤ implemented. áá(2⌐ OutbounΣ INITIAT┼ RECOVER┘ message≤ arσ onl∙ valiΣ durinτ thσ ì asynchronou≤ even⌠ notificatioε protocol. èááTw∩-bytσ message≤ consis⌠ oµ tw∩ consecutivσ byte≤ transferreΣ durinτ ß ì MESSAG┼ phase« Thσ valuσ oµ thσ firs⌠ bytσ determine≤ whicΦ messagσ i≤ t∩ bσ ì performeΣ a≤ defineΣ iε Tablσ ╡-2« Thσ seconΣ bytσ i≤ ß paramete≥ bytσ whicΦ ì i≤ useΣ a≤ defineΣ iε thσ messagσ descriptioε (seσ 5.6). .cp3 áá┴ valuσ oµ onσ iε thσ firs⌠ bytσ oµ ß messagσ indicate≤ thσ beginninτ oµ ß ì multiplσ-bytσ extendeΣ message« Thσ minimuφ numbe≥ oµ byte≤ sen⌠ fo≥ aε ì extendeΣ messagσ i≤ three« Thσ extendeΣ messagσ forma⌠ anΣ thσ extendeΣ ì messagσ code≤ arσ showε iε Table≤ ╡-│ anΣ ╡-4¼ respectively. .aw off .pm 0 .cp 15 Table 5-3: Extended Message Format ============================================================================== Byte | Value | Description | ============================================================================== 0 | 01h | Extended message | ----------|----------|-------------------------------------------------------| 1 | n | Extended message length | ----------|----------|-------------------------------------------------------| 2 | y | Extended message code | ----------|----------|-------------------------------------------------------| 3 - n+1 | x | Extended message arguments | ============================================================================== .aw on .pm 3 ááThσ extendeΣ messagσ lengtΦ specifie≤ thσ lengtΦ iε byte≤ oµ thσ extendeΣ ì messagσ codσ plu≤ thσ extendeΣ messagσ argument≤ t∩ follow« Therefore¼ thσ ì tota∞ lengtΦ oµ thσ messagσ i≤ equa∞ t∩ thσ extendeΣ messagσ lengtΦ plu≤ two« ì ┴ valuσ oµ zer∩ fo≥ thσ extendeΣ messagσ lengtΦ indicate≤ 25╢ byte≤ follow. ááThσ extendeΣ messagσ code≤ arσ listeΣ iε Tablσ ╡-4« Thσ extendeΣ messagσ ì argument≤ arσ specifieΣ withiε thσ extendeΣ messagσ descriptions. .cp 12 .aw off .pm 0 Table 5-4: Extended Message Codes ============================================================================== Code (y) Description ------------------------------------------------------------------------------ 02h ReserveΣ (Seσ Notσ) 00h MODIFY DATA POINTER 01h SYNCHRONOUS DATA TRANSFER REQUEST 03h WIDE DATA TRANSFER REQUEST 04h - 7Fh Reserved 80h - FFh Vendor Unique ============================================================================== .aw on .pm3 .lm 3 ááNOTE║ ExtendeΣ messagσ codσ 02Φ wa≤ useΣ fo≥ thσ EXTENDE─ IDENTIF┘ messagσ ì ááiε SCS╔-1. .lm 1 .cp 3 ááThσ firs⌠ messagσ sen⌠ b∙ thσ initiato≥ afte≥ thσ SELECTIO╬ phasσ shal∞ bσ ì aε IDENTIFY¼ ABORT¼ o≥ BU╙ DEVIC┼ RESE╘ message« Iµ ß targe⌠ receive≤ an∙ ì othe≥ messagσ i⌠ shal∞ g∩ t∩ BU╙ FRE┼ phasσ (seσ unexpecteΣ disconnect¼ ì 5.1.1). èááIµ thσ firs⌠ messagσ i≤ aε IDENTIF┘ message¼ theε i⌠ ma∙ bσ immediatel∙ ì followeΣ b∙ othe≥ messages¼ sucΦ a≤ thσ firs⌠ oµ ß pai≥ oµ SYNCHRONOU╙ DAT┴ ì TRANSFE╥ REQUES╘ messages« Iµ taggeΣ queuinτ i≤ useΣ thσ queuσ taτ messagσ ì immediatel∙ follow≤ thσ IDENTIF┘ messagσ (seσ 5.6.7)« Thσ IDENTIF┘ messagσ ì establishe≤ ß logica∞ connectioε betweeε thσ initiato≥ anΣ thσ specifieΣ ì logica∞ uni⌠ o≥ targe⌠ routinσ withiε thσ targe⌠ knowε a≤ aε I_T_╠ nexu≤ o≥ ì I_T_╥ nexus« Afte≥ thσ RESELECTIO╬ phase¼ thσ target'≤ firs⌠ messagσ shal∞ bσ ì IDENTIFY« Thi≤ allow≤ thσ I_T_╠ nexu≤ o≥ I_T_╥ nexu≤ t∩ bσ rσ-established« ì Onl∙ onσ logica∞ uni⌠ o≥ targe⌠ routinσ shal∞ bσ identifieΣ fo≥ an∙ ì connection╗ iµ ß targe⌠ receive≤ ß seconΣ IDENTIF┘ messagσ witΦ ß differen⌠ ì logica∞ uni⌠ numbe≥ o≥ targe⌠ routinσ numbe≥ durinτ ß connection¼ i⌠ shal∞ g∩ ì t∩ BU╙ FRE┼ phasσ (seσ unexpecteΣ disconnect¼ 5.1.1)« Thσ treatmen⌠ oµ othe≥ ì logica∞ uni⌠ addressinτ error≤ i≤ describeΣ iε 6.5. ááAl∞ initiator≤ shal∞ implemen⌠ thσ mandator∙ message≤ tabulateΣ iε thσ ì "Initó columε oµ Tablσ ╡-2« Al∞ target≤ shal∞ implemen⌠ thσ mandator∙ ì message≤ tabulateΣ iε thσ "Targó columε oµ Tablσ ╡-2« ááWheneve≥ aε I_T_╠ nexu≤ o≥ I_T_╥ nexu≤ i≤ establisheΣ b∙ aε initiato≥ tha⌠ ì i≤ allowinτ disconnection¼ thσ initiato≥ shal∞ ensurσ tha⌠ thσ activσ pointer≤ ì arσ equa∞ t∩ thσ saveΣ pointer≤ fo≥ tha⌠ particula≥ logica∞ uni⌠ o≥ targe⌠ ì routine« Aε implieΣ restorσ pointer≤ operatioε shal∞ occu≥ a≤ ß resul⌠ oµ ß ì reconnection. .cp 10 .aw off .pm 0 5.6. Messages .aw on .pm 3 ááThσ SCS╔ message≤ arσ defineΣ iε thi≤ section. .cp 5 .aw off .pm 0 5.6.1. ABORT .aw on .pm 3 ááThσ ABOR╘ messagσ i≤ sen⌠ froφ thσ initiato≥ t∩ thσ targe⌠ t∩ clea≥ thσ ì active I/╧ proces≤ plu≤ an∙ queueΣ I/╧ proces≤ fo≥ thσ I_T_° nexus« Thσ ì targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ followinτ successfu∞ receip⌠ oµ thi≤ ì message« Thσ pendinτ data¼ status¼ anΣ queueΣ I/╧ processe≤ fo≥ an∙ othe≥ ì I_T_° nexu≤ shal∞ no⌠ bσ cleared. ááIµ onl∙ aε I_╘ nexu≤ ha≤ beeε established¼ thσ targe⌠ shal∞ g∩ t∩ thσ BU╙ ì FRE┼ phase« N∩ statu≤ o≥ messagσ shal∞ bσ sen⌠ fo≥ thσ curren⌠ I/╧ proces≤ ì anΣ n∩ othe≥ I/╧ proces≤ shal∞ bσ affected. .lm 3 ááIMPLEMENTOR╙ NOTE║ Thσ ABOR╘ messagσ iε thσ casσ oµ onl∙ aε I_╘ nexu≤ i≤ ì ááusefu∞ t∩ aε initiato≥ tha⌠ canno⌠ ge⌠ aε IDENTIF┘ messagσ througΦ t∩ thσ ì áátarge⌠ duσ t∩ parit∙ error≤ anΣ jus⌠ need≤ t∩ enΣ thσ curren⌠ connection« ì ááAn∙ pendinτ data¼ status¼ o≥ queueΣ I/╧ processe≤ fo≥ thσ I_╘ nexu≤ i≤ no⌠ ì ááaffected. .lm 1 ááI⌠ i≤ no⌠ aε erro≥ t∩ issuσ thi≤ messagσ t∩ aε I_T_° nexu≤ tha⌠ doe≤ no⌠ ì havσ aε activσ o≥ queueΣ I/╧ process. ááPreviousl∙ establisheΣ conditions¼ includinτ MOD┼ SELEC╘ parameters¼ ì reservations¼ anΣ extendeΣ contingen⌠ allegiancσ shal∞ no⌠ bσ changeΣ b∙ thσ ì ABOR╘ message. .cp 9è.lm 3 ááIMPLEMENTOR╙ NOTES║ Thσ BU╙ DEVIC┼ RESET¼ CLEA╥ QUEUE¼ ABORT¼ anΣ ABOR╘ TA╟ ì áámessage≤ providσ ß mean≤ t∩ clea≥ onσ o≥ morσ I/╧ processe≤ prio≥ t∩ norma∞ ì áátermination« Thσ BU╙ DEVIC┼ RESE╘ messagσ clear≤ al∞ I/╧ processe≤ fo≥ al∞ ì ááinitiator≤ oε al∞ logica∞ unit≤ anΣ al∞ targe⌠ routine≤ oµ thσ target« Thσ ì ááCLEA╥ QUEU┼ messagσ clear≤ al∞ I/╧ processe≤ fo≥ al∞ initiator≤ oε thσ ì ááspecifieΣ logica∞ uni⌠ o≥ targe⌠ routinσ oµ thσ target« Thσ ABOR╘ messagσ ì ááclear≤ al∞ I/╧ processe≤ fo≥ thσ selectinτ initiato≥ oε thσ specifieΣ ì áálogica∞ uni⌠ o≥ targe⌠ routinσ oµ thσ target« Thσ ABOR╘ TA╟ messagσ clear≤ ì ááthσ current I/╧ proces≤ only. .lm 1 .cp 15 .aw off .pm 0 5.6.2. ABORT TAG .aw on .pm 3 ááThσ ABOR╘ TA╟ messagσ shal∞ bσ implementeΣ iµ taggeΣ queuinτ i≤ implemented« ì Thσ targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ followinτ successfu∞ receip⌠ oµ thi≤ ì message« Thσ targe⌠ shal∞ clea≥ thσ curren⌠ I/╧ process« Iµ thσ targe⌠ ha≤ ì alread∙ starteΣ executioε oµ thσ I/╧ process¼ thσ executioε shal∞ bσ halted« ì Thσ mediuφ content≤ ma∙ havσ beeε modifieΣ beforσ thσ executioε wa≤ halted« ì Iε eithe≥ case¼ an∙ pendinτ statu≤ o≥ datß fo≥ thσ I/╧ proces≤ shal∞ bσ ì cleareΣ anΣ n∩ statu≤ o≥ endinτ messagσ shal∞ bσ sen⌠ t∩ thσ initiator« ì Pendinτ status¼ data¼ anΣ command≤ fo≥ othe≥ activσ o≥ queueΣ I/╧ processe≤ ì shal∞ no⌠ bσ affected« Executioε oµ othe≥ I/╧ processe≤ queueΣ fo≥ thσ I_T_° ì nexu≤ shal∞ no⌠ bσ aborted. ááPreviousl∙ establisheΣ conditions¼ includinτ MOD┼ SELEC╘ parameters¼ ì reservations¼ anΣ extendeΣ contingen⌠ allegiancσ shal∞ no⌠ bσ changeΣ b∙ thσ ì ABOR╘ TA╟ message. .cp 10 .aw off .pm 0 5.6.3. BUS DEVICE RESET .aw on .pm 3 ááThσ BU╙ DEVIC┼ RESE╘ messagσ i≤ sen⌠ froφ aε initiato≥ t∩ direc⌠ ß targe⌠ t∩ ì clea≥ al∞ I/╧ processe≤ oε tha⌠ SCS╔ device« Thi≤ messagσ force≤ ß harΣ rese⌠ ì conditioε t∩ thσ selecteΣ SCS╔ device« Thσ targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ ì phasσ followinτ successfu∞ receip⌠ oµ thi≤ message« Thσ targe⌠ shal∞ creatσ ß ì uni⌠ attentioε conditioε fo≥ al∞ initiator≤ (seσ 6.9). .cp 17 .aw off .pm 0 5.6.4. CLEAR QUEUE .aw on .pm 3 ááThσ CLEA╥ QUEU┼ messagσ shal∞ bσ implementeΣ iµ taggeΣ queuinτ i≤ ì implementeΣ anΣ ma∙ bσ implementeΣ iµ untaggeΣ queuinτ i≤ implemented« Thσ ì targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ followinτ successfu∞ receip⌠ oµ thi≤ ì message« Thσ targe⌠ shal∞ perforφ aε actioε equivalen⌠ t∩ receivinτ ß serie≤ ì oµ ABOR╘ message≤ froφ eacΦ initiator« Al∞ I/╧ processes¼ froφ al∞ ì initiators¼ iε thσ queuσ fo≥ thσ specifieΣ logica∞ uni⌠ o≥ targe⌠ routinσ ì shal∞ bσ cleareΣ froφ thσ queue« Al∞ activσ I/╧ processe≤ shal∞ bσ ì terminated« Thσ mediuφ ma∙ havσ beeε altereΣ b∙ partiall∙ executeΣ commands« ì Al∞ pendinτ statu≤ anΣ datß fo≥ tha⌠ logica∞ uni⌠ o≥ targe⌠ routinσ fo≥ al∞ ì initiator≤ shal∞ bσ cleared« N∩ statu≤ o≥ messagσ shal∞ bσ sen⌠ fo≥ an∙ oµ ì thσ I/╧ processes« ┴ uni⌠ attentioε conditioε shal∞ bσ generateΣ fo≥ al∞ ì othe≥ initiator≤ witΦ I/╧ processe≤ tha⌠ eithe≥ werσ activσ o≥ werσ queueΣ fo≥ ì tha⌠ logica∞ uni⌠ o≥ targe⌠ routine« Wheε reportinτ thσ uni⌠ attentioε ì conditioε thσ additiona∞ sensσ codσ shal∞ bσ se⌠ t∩ COMMAND╙ CLEARE─ B┘ ì ANOTHE╥ INITIATOR. ááPreviousl∙ establisheΣ conditions¼ includinτ MOD┼ SELEC╘ parameters¼ ì reservations¼ anΣ extendeΣ contingen⌠ allegiancσ shal∞ no⌠ bσ changeΣ b∙ thσ ìèCLEA╥ QUEU┼ message. .cp 5 .aw off .pm 0 5.6.5. COMMAND COMPLETE .aw on .pm 3 ááThσ COMMAN─ COMPLET┼ messagσ i≤ sen⌠ froφ ß targe⌠ t∩ aε initiato≥ t∩ ì indicatσ tha⌠ thσ executioε oµ aε I/╧ proces≤ ha≤ completeΣ anΣ tha⌠ valiΣ ì statu≤ ha≤ beeε sen⌠ t∩ thσ initiator« Afte≥ successfull∙ sendinτ thi≤ ì message¼ thσ targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ b∙ releasinτ thσ BS┘ ì signal« Thσ targe⌠ shal∞ conside≥ thσ messagσ transmissioε t∩ bσ successfu∞ ì wheε i⌠ detect≤ thσ negatioε oµ AC╦ fo≥ thσ COMMAN─ COMPLET┼ messagσ witΦ thσ ì AT╬ signa∞ false« .lm 3 ááIMPLEMENTOR╙ NOTE║ Thσ I/╧ proces≤ ma∙ havσ completeΣ successfull∙ o≥ ì ááunsuccessfull∙ a≤ indicateΣ iε thσ status. .lm 1 .cp 5 .aw off .pm 0 5.6.6. DISCONNECT .aw on .pm 3 ááThσ DISCONNEC╘ messagσ i≤ sen⌠ froφ ß targe⌠ t∩ inforφ aε initiato≥ tha⌠ thσ ì presen⌠ connectioε i≤ goinτ t∩ bσ brokeε (thσ targe⌠ plan≤ t∩ disconnec⌠ b∙ ì releasinτ thσ BS┘ signal)¼ bu⌠ tha⌠ ß late≥ reconnec⌠ wil∞ bσ requireΣ iε ì orde≥ t∩ completσ thσ curren⌠ I/╧ process« Thi≤ messagσ shal∞ no⌠ causσ thσ ì initiato≥ t∩ savσ thσ datß pointer« Afte≥ successfull∙ sendinτ thi≤ message¼ ì thσ targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ b∙ releasinτ thσ BS┘ signal« Thσ ì targe⌠ shal∞ conside≥ thσ messagσ transmissioε t∩ bσ successfu∞ wheε i⌠ ì detect≤ thσ negatioε oµ thσ AC╦ signa∞ fo≥ thσ DISCONNEC╘ messagσ witΦ thσ AT╬ ì signa∞ false. ááTarget≤ whicΦ breaδ datß transfer≤ int∩ multiplσ connection≤ shal∞ enΣ eacΦ ì successfu∞ connectioε (excep⌠ possibl∙ thσ last⌐ witΦ ß SAV┼ DAT┴ POINTE╥ ¡ ì DISCONNEC╘ messagσ sequence. ááThi≤ messagσ ma∙ als∩ bσ sen⌠ froφ aε initiato≥ t∩ ß targe⌠ t∩ instruc⌠ thσ ì targe⌠ t∩ disconnec⌠ froφ thσ SCS╔ bus« Iµ thi≤ optioε i≤ supported¼ anΣ ì afte≥ thσ DISCONNEC╘ messagσ i≤ received¼ thσ targe⌠ shal∞ switcΦ t∩ MESSAG┼ ì I╬ phase¼ senΣ thσ DISCONNEC╘ messagσ t∩ thσ initiato≥ (possibl∙ precedeΣ b∙ ì SAV┼ DAT┴ POINTE╥ message)¼ anΣ theε disconnec⌠ b∙ releasinτ BSY« Afte≥ ì releasinτ thσ BS┘ signal¼ thσ targe⌠ shal∞ no⌠ participatσ iε anothe≥ ì ARBITRATIO╬ phasσ fo≥ a⌠ leas⌠ ß disconnectioε delay« Iµ thi≤ optioε i≤ no⌠ ì supporteΣ o≥ thσ targe⌠ canno⌠ disconnec⌠ a⌠ thσ timσ wheε i⌠ receive≤ thσ ì DISCONNEC╘ messagσ froφ thσ initiator¼ thσ targe⌠ shal∞ responΣ b∙ sendinτ ß ì MESSAG┼ REJEC╘ messagσ t∩ thσ initiator. .cp 5 .aw off .pm 0 5.6.7. IDENTIF┘ .aw on .pm 3 ááThσ IDENTIF┘ messagσ (Tablσ ╡-5⌐ i≤ sen⌠ b∙ eithe≥ thσ initiato≥ o≥ thσ ì targe⌠ t∩ establisΦ aε I_T_╠ nexu≤ o≥ aε I_T_╥ nexus. .lm 3 ááIMPLEMENTOR╙ NOTE║ Usσ oµ thσ IDENTIF┘ messagσ t∩ establisΦ aε I_T_╥ nexu≤ ì ááallow≤ connectioε t∩ onσ oµ u≡ t∩ eigh⌠ targe⌠ routine≤ o≥ function≤ iε thσ ì áátarge⌠ itself« Thesσ targe⌠ routine≤ arσ expecteΣ t∩ bσ useΣ fo≥ ì áámaintenancσ anΣ diagnostiπ purposes. .lm 1 .cp 10è.aw off .pm 0 Table 5-5: IDENTIF┘ Message Format ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 |Identify|DiscPriv| LUNTAR ⁿReservedⁿReservedⁿ LUNTRN | ============================================================================== .aw on .lm 1 .pm 3 ááThσ identif∙ bi⌠ shal∞ bσ se⌠ t∩ onσ t∩ specif∙ tha⌠ thi≤ i≤ aε IDENTIF┘ ì message. áá┴ disconnec⌠ privilegσ (DiscPriv⌐ bi⌠ oµ onσ specifie≤ tha⌠ thσ initiato≥ ì ha≤ granteΣ thσ targe⌠ thσ privilegσ oµ disconnecting« ┴ DiscPri÷ bi⌠ oµ zer∩ ì specifie≤ tha⌠ thσ targe⌠ shal∞ no⌠ disconnect« Thi≤ bi⌠ i≤ no⌠ defineΣ anΣ ì shal∞ bσ se⌠ t∩ zer∩ wheε aε IDENTIF┘ messagσ i≤ sen⌠ b∙ ß target. áá┴ logica∞ uni⌠ targe⌠ (LUNTAR⌐ bi⌠ oµ zer∩ specifie≤ tha⌠ thσ I/╧ proces≤ i≤ ì directeΣ t∩ o≥ froφ ß logica∞ unit« ┴ LUNTA╥ bi⌠ oµ onσ specifie≤ tha⌠ thσ ì I/╧ proces≤ i≤ directeΣ t∩ o≥ froφ ß targe⌠ routine« ááThσ logica∞ uni⌠ numbe≥ targe⌠ routinσ numbe≥ (LUNTRN⌐ fielΣ specifie≤ ß ì logica∞ uni⌠ numbe≥ iµ thσ LUNTA╥ bi⌠ i≤ zero« Thσ LUNTR╬ fielΣ specifie≤ ß ì targe⌠ routinσ numbe≥ iµ thσ LUNTA╥ bi⌠ i≤ one« Thσ responsσ t∩ aε invaliΣ ì valuσ iε thσ LUNTR╬ fielΣ i≤ describeΣ iε 6.5.3« Onl∙ thσ INQUIR┘ anΣ REQUES╘ ì SENS┼ command≤ arσ valiΣ fo≥ targe⌠ routines« Iµ ß targe⌠ receive≤ an∙ othe≥ ì commanΣ fo≥ ß targe⌠ routine¼ i⌠ shal∞ returε CHEC╦ CONDITIO╬ statu≤ anΣ shal∞ ì se⌠ thσ sensσ ke∙ t∩ ILLEGA╠ REQUEST. ááAε IDENTIF┘ messagσ i≤ invaliΣ iµ ß reserveΣ bi⌠ i≤ se⌠ t∩ onσ o≥ iµ thσ ì LUNTA╥ bi⌠ i≤ se⌠ t∩ onσ anΣ thσ targe⌠ doe≤ no⌠ implemen⌠ targe⌠ routines« ┴ ì devicσ ma∙ responΣ t∩ aε invaliΣ IDENTIF┘ messagσ b∙ immediatel∙ sendinτ ß ì MESSAG┼ REJEC╘ messagσ o≥ b∙ returninτ CHEC╦ CONDITIO╬ status« Iµ ß CHEC╦ ì CONDITIO╬ statu≤ i≤ returned¼ thσ sensσ ke∙ shal∞ bσ se⌠ t∩ ILLEGA╠ REQUES╘ ì anΣ thσ additiona∞ sensσ codσ shal∞ bσ se⌠ t∩ INVALI─ BIT╙ I╬ IDENTIF┘ MESSAG┼ ì FIELD. ááOnl∙ onσ logica∞ uni⌠ numbe≥ o≥ targe⌠ routinσ numbe≥ shal∞ bσ identifieΣ ì pe≥ I/╧ process« Thσ initiato≥ ma∙ senΣ onσ o≥ morσ IDENTIF┘ message≤ durinτ ì ß connection« ┴ seconΣ IDENTIF┘ messagσ witΦ ß differen⌠ valuσ iε eithe≥ thσ ì LUNTA╥ bi⌠ o≥ LUNTR╬ fielΣ shal∞ no⌠ bσ issueΣ beforσ ß BU╙ FRE┼ phasσ ha≤ ì occurred╗ iµ ß targe⌠ receive≤ ß seconΣ IDENTIF┘ messagσ witΦ ß differen⌠ ì valuσ iε eithe≥ oµ thesσ fields¼ i⌠ shal∞ g∩ t∩ BU╙ FRE┼ phasσ (seσ unexpecteΣ ì disconnect¼ 5.1.1)« Thu≤ aε initiato≥ ma∙ changσ thσ DiscPri÷ bit¼ bu⌠ ma∙ ì no⌠ attemp⌠ t∩ switcΦ t∩ anothe≥ I/╧ process« (Seσ thσ DTD├ fielΣ oµ thσ ì disconnec⌠-reconnec⌠ pagσ (7.3.3.2⌐ fo≥ additiona∞ control≤ ove≥ ì disconnection.) ááAε implieΣ RESTOR┼ POINTER╙ messagσ shal∞ bσ performeΣ b∙ thσ initiato≥ ì prio≥ t∩ thσ assertioε oµ thσ AC╦ signa∞ oε thσ nex⌠ phasσ fo≥ aε inbounΣ ì IDENTIF┘ messagσ sen⌠ durinτ reconnection. .cp 5è.aw off .pm 0 5.6.8. IGNORE WIDE RESIDUE .aw on .pm 3 .aw off .pm 0 Table 5-6: IGNOR┼ WID┼ RESIDUE Message Format ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 ⁿ Messagσ Codσ (23h) | -----|-----------------------------------------------------------------------| ▒ ⁿ Ignorσ | ============================================================================== .aw on .lm 1 .pm 3 ááThσ IGNOR┼ WID┼ RESIDU┼ messagσ (Tablσ ╡-6⌐ shal∞ bσ sen⌠ froφ ß targe⌠ t∩ ì indicatσ tha⌠ thσ numbe≥ oµ valiΣ byte≤ sen⌠ durinτ thσ las⌠ REQ/AC╦ handshakσ ì anΣ REQB/ACK┬ handshakσ oµ ß DAT┴ I╬ phasσ i≤ les≤ thaε thσ negotiateΣ ì transfe≥ width« Thσ ignorσ fielΣ indicate≤ thσ numbe≥ oµ invaliΣ datß byte≤ ì transferred« Thi≤ messagσ shal∞ bσ sen⌠ immediatel∙ followinτ thσ DAT┴ I╬ ì phasσ anΣ prio≥ t∩ an∙ othe≥ messages« Thσ ignorσ fielΣ i≤ defineΣ a≤ ì follows: .aw off .pm 0 InvaliΣ Datß Bit≤ Ignore 32-bi⌠ Transfer≤ 16-bi⌠ Transfers -----¡---- ---------------¡ ---------------- 00Φ Reserved Reserved 01Φ DB(31-24) DB(15-8) 02Φ DB(31-16) Reserved 03Φ DB(31-8) Reserved 04Φ t∩ FFΦ Reserved Reserved .aw on .pm 3 ááEveε thougΦ ß bytσ i≤ invaliΣ it≤ correspondinτ parit∙ bi⌠ shal∞ bσ valiΣ ì fo≥ thσ valuσ transferred« Fo≥ 1╢-bi⌠ transfers¼ DB(3▒-16⌐ arσ alway≤ invaliΣ ì anΣ thσ correspondinτ parit∙ bit≤ arσ als∩ invalid. .cp 5 .aw off .pm 0 5.6.9. INITIATE RECOVERY .aw on .pm 3 áá┴ targe⌠ tha⌠ support≤ extendeΣ contingen⌠ allegiancσ shal∞ inforφ thσ ì initiato≥ i⌠ i≤ enterinτ thi≤ conditioε b∙ sendinτ aε INITIAT┼ RECOVER┘ ì messagσ immediatel∙ followinτ ß CHEC╦ CONDITIO╬ o≥ COMMAN─ TERMINATE─ status« ì Thσ extendeΣ contingen⌠ allegiancσ conditioε remain≤ iε effec⌠ unti∞ ì terminateΣ a≤ describeΣ iε 6.7. ááIµ aε asynchronou≤ even⌠ occurs¼ thσ targe⌠ ma∙ ente≥ aε extendeΣ contingen⌠ ì allegiancσ conditioε b∙ becominτ ß temporar∙ initiato≥ anΣ sendinτ thσ ì INITIAT┼ RECOVER┘ messagσ followinτ thσ IDENTIF┘ messagσ anΣ an∙ queuσ taτ ì messagσ anΣ beforσ thσ COMMAN─ phasσ oµ thσ SEN─ commanΣ tha⌠ i≤ useΣ t∩ ì perforφ thσ asynchronou≤ even⌠ notificatioε (seσ 6.5.5)« Thσ successfu∞ ì transmissioε oµ thi≤ messagσ establishe≤ thσ extendeΣ contingen⌠ allegiancσ ì conditioε whicΦ remain≤ iε effec⌠ unti∞ terminateΣ a≤ describeΣ iε 6.7. .cp 5è.lm3 .pm0 .aw1 ááIMPLEMENTOR╙ NOTE║ Iµ thσ targe⌠ notifie≤ multiplσ initiator≤ oµ thσ ì ááasynchronou≤ event¼ i⌠ shoulΣ includσ thσ INITIAT┼ RECOVER┘ messagσ iε onl∙ ì ááonσ oµ thσ notifications. .lm1 .pm3 .aw1 áá┴ MESSAG┼ REJEC╘ responsσ t∩ aε INITIAT┼ RECOVER┘ messagσ indicate≤ tha⌠ aε ì extendeΣ contingen⌠ allegiancσ conditioε shal∞ no⌠ bσ established« Thσ ì enableΣ o≥ disableΣ statσ oµ aε extendeΣ contingen⌠ allegiancσ (seσ thσ DQuσ ì bi⌠ oµ thσ contro∞ modσ page¼ 7.3.3.1⌐ i≤ no⌠ changeΣ b∙ thσ rejectioε oµ aε ì INITIAT┼ RECOVER┘ message. .cp 5 .aw off .pm 0 5.6.10. INITIATOR DETECTED ERROR .aw on .pm 3 ááThσ INITIATO╥ DETECTE─ ERRO╥ messagσ i≤ sen⌠ froφ aε initiato≥ t∩ inforφ ß ì targe⌠ tha⌠ aε erro≥ ha≤ occurreΣ tha⌠ doe≤ no⌠ precludσ thσ targe⌠ froφ ì retryinτ thσ operation« Thσ sourcσ oµ thσ erro≥ ma∙ eithe≥ bσ relateΣ t∩ ì previou≤ activitie≤ oε thσ SCS╔ bu≤ o≥ ma∙ bσ interna∞ t∩ thσ initiato≥ anΣ ì unrelateΣ t∩ an∙ previou≤ SCS╔ bu≤ activity« AlthougΦ presen⌠ pointe≥ ì integrit∙ i≤ no⌠ assured¼ ß RESTOR┼ POINTER╙ messagσ o≥ ß disconnec⌠ followeΣ ì b∙ ß reconnect¼ shal∞ causσ thσ pointer≤ t∩ bσ restoreΣ t∩ thei≥ defineΣ prio≥ ì state. .cp 5 .aw off .pm 0 5.6.11. LINKED COMMAND COMPLETE .aw on .pm 3 ááThσ LINKE─ COMMAN─ COMPLET┼ messagσ i≤ sen⌠ froφ ß targe⌠ t∩ aε initiato≥ t∩ ì indicatσ tha⌠ thσ executioε oµ ß linkeΣ commanΣ ha≤ completeΣ anΣ tha⌠ statu≤ ì ha≤ beeε sent« Thσ initiato≥ shal∞ theε se⌠ thσ pointer≤ t∩ thσ initia∞ statσ ì fo≥ thσ nex⌠ linkeΣ command. .cp 5 .aw off .pm 0 5.6.12. LINKED COMMAND COMPLETE (WITH FLAG) .aw on .pm 3 ááThσ LINKE─ COMMAN─ COMPLET┼ (WIT╚ FLAG⌐ messagσ i≤ sen⌠ froφ ß targe⌠ t∩ aε ì initiato≥ t∩ indicatσ tha⌠ thσ executioε oµ ß linkeΣ commanΣ (witΦ thσ flaτ ì bi⌠ se⌠ t∩ one⌐ ha≤ completeΣ anΣ tha⌠ statu≤ ha≤ beeε sent« Thσ initiato≥ ì shal∞ theε se⌠ thσ pointer≤ t∩ thσ initia∞ statσ oµ thσ nex⌠ linkeΣ command« ì Typicall∙ thi≤ messagσ woulΣ bσ useΣ t∩ causσ aε interrup⌠ iε thσ initiato≥ ì betweeε tw∩ linkeΣ commands. .cp 5 .aw off .pm 0 5.6.13. MESSAGE PARITY ERROR .aw on .pm 3 ááThσ MESSAG┼ PARIT┘ ERRO╥ messagσ i≤ sen⌠ froφ thσ initiato≥ t∩ thσ targe⌠ t∩ ì indicatσ tha⌠ thσ las⌠ messagσ bytσ i⌠ receiveΣ haΣ ß parit∙ error. .cp 7 ááIε orde≥ t∩ indicatσ it≤ intention≤ oµ sendinτ thi≤ message¼ thσ initiato≥ ì shal∞ asser⌠ thσ AT╬ signa∞ prio≥ t∩ it≤ releasσ oµ thσ AC╦ signa∞ fo≥ thσ ì REQ/AC╦ handshakσ oµ thσ messagσ bytσ tha⌠ ha≤ thσ parit∙ error« Thi≤ ì provide≤ aε interlocδ s∩ tha⌠ thσ targe⌠ caε determinσ whicΦ messagσ bytσ ha≤ ì thσ parit∙ error« Iµ thσ targe⌠ receive≤ thi≤ messagσ unde≥ an∙ othe≥ ì circumstance¼ i⌠ shal∞ signa∞ ß catastrophiπ erro≥ conditioε b∙ releasinτ thσ ì BS┘ signa∞ withou⌠ an∙ furthe≥ informatioε transfe≥ attemp⌠ (seσ 5.1.1)« ááIµ thσ targe⌠ return≤ t∩ thσ MESSAG┼ I╬ phasσ beforσ switchinτ t∩ somσ othe≥ ì phase¼ afte≥ receivinτ thσ MESSAG┼ PARIT┘ ERRO╥ message¼ thσ targe⌠ shal∞ rσ-ì senΣ thσ entirσ messagσ tha⌠ haΣ thσ parit∙ error. .cp 5è.aw off .pm 0 5.6.14. MESSAGE REJECT .aw on .pm 3 ááThσ MESSAG┼ REJEC╘ messagσ i≤ sen⌠ froφ eithe≥ thσ initiato≥ o≥ targe⌠ t∩ ì indicatσ tha⌠ thσ las⌠ messagσ o≥ messagσ bytσ i⌠ receiveΣ wa≤ inappropriatσ ì o≥ ha≤ no⌠ beeε implemented. ááIε orde≥ t∩ indicatσ it≤ intention≤ oµ sendinτ thi≤ message¼ thσ initiato≥ ì shal∞ asser⌠ thσ AT╬ signa∞ prio≥ t∩ it≤ releasσ oµ thσ AC╦ signa∞ fo≥ thσ ì REQ/AC╦ handshakσ oµ thσ messagσ bytσ tha⌠ i≤ t∩ bσ rejected« Iµ thσ targe⌠ ì receive≤ thi≤ messagσ unde≥ an∙ othe≥ circumstance¼ i⌠ shal∞ rejec⌠ thi≤ ì message« ááWheε ß targe⌠ send≤ thi≤ message¼ i⌠ shal∞ changσ t∩ MESSAG┼ I╬ phasσ anΣ ì senΣ thi≤ messagσ prio≥ t∩ requestinτ additiona∞ messagσ byte≤ froφ thσ ì initiator« Thi≤ provide≤ aε interlocδ s∩ tha⌠ thσ initiato≥ caε determinσ ì whicΦ messagσ bytσ i≤ rejected. ááAfte≥ ß targe⌠ send≤ ß MESSAG┼ REJEC╘ messagσ anΣ iµ thσ AT╬ signa∞ i≤ stil∞ ì asserted¼ theε i⌠ shal∞ returε t∩ thσ MESSAG┼ OU╘ phase« Thσ subsequen⌠ ì MESSAG┼ OU╘ phasσ shal∞ begiε witΦ thσ firs⌠ bytσ oµ ß message. .cp 27 .aw off .pm 0 5.6.15. MODIF┘ DAT┴ POINTE╥ Messagσ Table 5-7: MODIFY DATA POINTER ============================================================================== Byte | Value | Description | ============================================================================== 0 | 01h | Extended message | -----|---------|-------------------------------------------------------------| 1 | 05h | Extended message length | -----|---------|-------------------------------------------------------------| 2 | 00h | MODIFY DATA POINTER code | -----|---------|-------------------------------------------------------------| 3 | x | Argument (Mos⌠ Significan⌠ Byte) | -----|---------|-------------------------------------------------------------| 4 | x | Argument | -----|---------|-------------------------------------------------------------| 5 | x | Argument | -----|---------|-------------------------------------------------------------| 6 | x | Argument (Leas⌠ Significan⌠ Byte) | ============================================================================== .aw on .pm 3 ááThσ MODIF┘ DAT┴ POINTE╥ messagσ (Tablσ ╡-7⌐ i≤ sen⌠ froφ thσ targe⌠ t∩ thσ ì initiato≥ anΣ request≤ tha⌠ thσ signeΣ argumen⌠ bσ addeΣ (two'≤ complement⌐ t∩ ì thσ valuσ oµ thσ curren⌠ datß pointer. .cp 5 .aw off .pm 0 5.6.16. NO OPERATION .aw on .pm 3 ááThσ N╧ OPERATIO╬ messagσ i≤ sen⌠ froφ aε initiato≥ iε responsσ t∩ ß target'≤ ì reques⌠ fo≥ ß messagσ wheε thσ initiato≥ doe≤ no⌠ currentl∙ havσ an∙ othe≥ ì valiΣ messagσ t∩ send. ááFo≥ example¼ iµ thσ targe⌠ doe≤ no⌠ responΣ t∩ thσ attentioε conditioε unti∞ ìèß late≥ phasσ anΣ a⌠ tha⌠ timσ thσ origina∞ messagσ i≤ n∩ longe≥ valiΣ thσ ì initiato≥ ma∙ senΣ thσ N╧ OPERATIO╬ messagσ wheε thσ targe⌠ enter≤ thσ MESSAG┼ ì OU╘ phase. .cp 15 .aw off .pm 0 5.6.17. Queuσ Tag Messages .aw on .pm 3 .aw off .pm 0 Table 5-8: Queuσ Tag Message Format ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 ⁿ Messagσ Codσ (20Φ o≥ 21Φ o≥ 22h) | -----|-----------------------------------------------------------------------| ▒ ⁿ Queuσ Tag | ============================================================================== .aw on .lm 1 .pm 3 .cp3 ááTablσ ╡-╕ define≤ thσ forma⌠ fo≥ thσ queuσ taτ messages« Iµ thσ targe⌠ ì implement≤ taggeΣ queuing¼ al∞ oµ thσ queuσ taτ message≤ arσ mandatory║ HEA─ ì O╞ QUEU┼ TAG¼ ORDERE─ QUEU┼ TAG¼ anΣ SIMPL┼ QUEU┼ TAG« TaggeΣ queuinτ i≤ onl∙ ì defineΣ fo≥ logica∞ units¼ no⌠ targe⌠ routines. .cp 3 ááIµ ß targe⌠ doe≤ no⌠ implemen⌠ taggeΣ queuinτ anΣ ß queuσ taτ messagσ i≤ ì receiveΣ o≥ iµ ß queuσ taτ messagσ i≤ receiveΣ fo≥ ß targe⌠ routine¼ i⌠ shal∞ ì responΣ witΦ ß MESSAG┼ REJEC╘ messagσ anΣ accep⌠ thσ I/╧ proces≤ a≤ iµ i⌠ werσ ì untagged. .cp 3 ááThσ queuσ taτ message≤ arσ useΣ t∩ specif∙ aε identifier¼ calleΣ ß queuσ ì tag¼ fo≥ aε I/╧ proces≤ whicΦ establishe≤ thσ I_T_L_╤ nexus« Thσ queuσ taτ ì fielΣ i≤ aε ╕-bi⌠ unsigneΣ intege≥ assigneΣ b∙ thσ initiato≥ durinτ aε initia∞ ì connection« Thσ queuσ taτ fo≥ ever∙ I/╧ proces≤ fo≥ eacΦ I_T_╠ nexu≤ shoulΣ ì bσ unique« Iµ thσ targe⌠ receive≤ ß queuσ taτ tha⌠ i≤ currentl∙ iε usσ fo≥ ì thσ I_T_╠ nexus¼ theε i⌠ shal∞ responΣ a≤ defineΣ iε 6.5.2« ┴ queuσ taτ ì become≤ availablσ fo≥ rσ-assignmen⌠ wheε thσ I/╧ proces≤ ends« Thσ numeriπ ì valuσ oµ ß queuσ taτ ha≤ n∩ effec⌠ oε thσ orde≥ oµ execution. .cp 3 .lm 3 ááIMPLEMENTOR╙ NOTE║ Fo≥ eacΦ logica∞ uni⌠ oε eacΦ target¼ eacΦ initiato≥ ha≤ ì ááu≡ t∩ 25╢ queuσ tag≤ t∩ assigε t∩ I/╧ processes« Thu≤ ß targe⌠ witΦ eigh⌠ ì áálogica∞ unit≤ coulΣ havσ u≡ t∩ 1433╢ I/╧ processe≤ concurrentl∙ iε existencσ ì ááiµ therσ werσ seveε initiator≤ oε thσ bus. .lm 1 .cp 3 ááWheneve≥ aε initiato≥ connect≤ t∩ ß target¼ thσ appropriatσ queuσ taτ ì messagσ shal∞ bσ sen⌠ immediatel∙ followinτ thσ IDENTIF┘ messagσ anΣ withiε ì thσ samσ MESSAG┼ OU╘ phasσ t∩ establisΦ thσ I_T_L_╤ nexu≤ fo≥ thσ I/╧ process« ì Onl∙ onσ I_T_L_╤ nexu≤ ma∙ bσ establisheΣ durinτ ß connection« Iµ ß queuσ taτ ì messagσ i≤ no⌠ sent¼ theε onl∙ aε I_T_° nexu≤ i≤ establisheΣ fo≥ thσ I/╧ ì proces≤ (untaggeΣ command). .cp 3 ááWheneve≥ ß targe⌠ reconnect≤ t∩ aε initiato≥ t∩ continuσ ß taggeΣ I/╧ ì process¼ thσ SIMPL┼ QUEU┼ TA╟ messagσ shal∞ bσ sen⌠ immediatel∙ followinτ thσ ì IDENTIF┘ messagσ anΣ withiε thσ samσ MESSAG┼ I╬ phasσ t∩ revivσ thσ I_T_L_╤ ì nexu≤ fo≥ thσ I/╧ process« Onl∙ onσ I_T_L_╤ nexu≤ ma∙ bσ reviveΣ durinτ ß ì reconnection« Iµ thσ SIMPL┼ QUEU┼ TA╟ messagσ i≤ no⌠ sent¼ theε onl∙ aε I_T_° ì nexu≤ i≤ reviveΣ fo≥ thσ I/╧ proces≤ (untaggeΣ command).è .cp 3 ááIµ ß targe⌠ attempt≤ t∩ reconnec⌠ usinτ aε invaliΣ queuσ tag¼ theε thσ ì initiato≥ shoulΣ responΣ witΦ aε ABOR╘ TA╟ message. .cp 5 .aw off .pm 0 5.6.17.1. HEA─ O╞ QUEU┼ TA╟ .aw on .pm 3 ááThσ HEA─ O╞ QUEU┼ TA╟ messagσ specifie≤ tha⌠ thσ I/╧ proces≤ bσ placeΣ firs⌠ ì iε tha⌠ logica∞ unit'≤ commanΣ queue« Aε I/╧ proces≤ alread∙ beinτ executeΣ ì b∙ thσ targe⌠ shal∞ no⌠ bσ prσ-empted« ┴ subsequen⌠ I/╧ proces≤ receiveΣ witΦ ì ß HEA─ O╞ QUEU┼ TA╟ messagσ shal∞ bσ placeΣ a⌠ thσ heaΣ oµ thσ commanΣ queuσ ì fo≥ executioε iε las⌠-in¼ firs⌠-ou⌠ order« .cp 5 .aw off .pm 0 5.6.17.2. ORDERED QUEUE TAG .aw on .pm 3 ááThσ ORDERE─ QUEU┼ TA╟ messagσ specifie≤ tha⌠ thσ I/╧ proces≤ bσ placeΣ iε ì tha⌠ logica∞ unit'≤ commanΣ queuσ fo≥ executioε iε thσ orde≥ received« Al∞ ì queueΣ I/╧ processe≤ fo≥ thσ logica∞ uni⌠ receiveΣ prio≥ t∩ thi≤ I/╧ proces≤ ì shal∞ bσ executeΣ beforσ thi≤ I/╧ proces≤ i≤ executed« Al∞ queueΣ I/╧ ì processe≤ receiveΣ afte≥ thi≤ I/╧ proces≤ shal∞ bσ executeΣ afte≥ thi≤ I/╧ ì process¼ excep⌠ fo≥ I/╧ processe≤ receiveΣ witΦ ß HEA─ O╞ QUEU┼ TA╟ message. .cp 5 .aw off .pm 0 5.6.17.3. SIMPLE QUEUE TAG .aw on .pm 3 ááThσ SIMPL┼ QUEU┼ TA╟ messagσ specifie≤ tha⌠ thσ I/╧ proces≤ bσ placeΣ iε ì tha⌠ logica∞ unit'≤ commanΣ queue« Thσ orde≥ oµ executioε i≤ describeΣ iε ì 6.8. .cp 5 .aw off .pm 0 5.6.18. RELEASE RECOVERY .aw on .pm 3 ááThσ RELEAS┼ RECOVER┘ messagσ i≤ sen⌠ froφ aε initiato≥ t∩ ß targe⌠ t∩ ì terminatσ aε extendeΣ contingen⌠ allegiancσ conditioε previousl∙ establisheΣ ì b∙ aε INITIAT┼ RECOVER┘ message« Thi≤ messagσ shal∞ bσ sen⌠ immediatel∙ ì followinτ thσ IDENTIF┘ messagσ iε thσ samσ MESSAG┼ OU╘ phase« Thσ extendeΣ ì contingen⌠ allegiancσ conditioε end≤ upoε successfu∞ receip⌠ oµ thσ RELEAS┼ ì RECOVER┘ message« Thσ targe⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ followinτ ì successfu∞ receip⌠ oµ thi≤ message. .cp 3 ááIµ ß RELEAS┼ RECOVER┘ messagσ i≤ receiveΣ b∙ ß targe⌠ tha⌠ implement≤ ì extendeΣ contingen⌠ allegiancσ wheε n∩ extendeΣ contingen⌠ allegiancσ ì conditioε i≤ active¼ thσ messagσ shal∞ no⌠ bσ rejecteΣ anΣ thσ targe⌠ shal∞ g∩ ì t∩ thσ BU╙ FRE┼ phase. .cp 5 .aw off .pm 0 5.6.19. RESTORE POINTERS .aw on .pm 3 ááThσ RESTOR┼ POINTER╙ messagσ i≤ sen⌠ froφ ß targe⌠ t∩ direc⌠ thσ initiato≥ ì t∩ cop∙ thσ mos⌠ recentl∙ saveΣ command¼ data¼ anΣ statu≤ pointer≤ fo≥ thσ I/╧ ì proces≤ t∩ thσ correspondinτ activσ pointers« Thσ commanΣ anΣ statu≤ pointer≤ ì shal∞ bσ restoreΣ t∩ thσ beginninτ oµ thσ presen⌠ commanΣ anΣ statu≤ areas« ì Thσ datß pointe≥ shal∞ bσ restoreΣ t∩ thσ valuσ a⌠ thσ beginninτ oµ thσ datß ì areß iε thσ absencσ oµ ß SAV┼ DAT┴ POINTE╥ messagσ o≥ t∩ thσ valuσ a⌠ thσ ì poin⌠ a⌠ whicΦ thσ las⌠ SAV┼ DAT┴ POINTE╥ messagσ occurreΣ fo≥ tha⌠ nexus. .cp 5 .aw off .pm 0 5.6.20. SAVE DATA POINTER .aw on .pm 3 ááThσ SAV┼ DAT┴ POINTE╥ messagσ i≤ sen⌠ froφ ß targe⌠ t∩ direc⌠ thσ initiato≥ ì t∩ cop∙ thσ activσ datß pointe≥ t∩ thσ saveΣ datß pointe≥ fo≥ thσ curren⌠ I/╧ ì process« (Seσ 5.┤ fo≥ ß definitioε oµ pointers.) è.cp 20 .aw off .pm 0 5.6.21. SYNCHRONOUS DATA TRANSFER REQUEST Message Table 5-9: SYNCHRONOUS DATA TRANSFER REQUEST ============================================================================== Byte | Value | Description | ============================================================================== 0 | 01h | Extended message | -----|---------|-------------------------------------------------------------| 1 | 03h | Extended message length | -----|---------|-------------------------------------------------------------| 2 | 01h | SYNCHRONOUS DATA TRANSFER REQUEST code | -----|---------|-------------------------------------------------------------| 3 | m | Transfer period (m times 4 nanoseconds) | -----|---------|-------------------------------------------------------------| 4 | x | REQ/ACK offset | ============================================================================== .aw on .pm 3 .cp 3 áá┴ SYNCHRONOU╙ DAT┴ TRANSFE╥ REQUES╘ (SDTR⌐ messagσ (Tablσ ╡-9⌐ exchangσ ì shal∞ bσ initiateΣ b∙ aε SCS╔ devicσ wheneve≥ ß previousl∙-arrangeΣ datß ì transfe≥ agreemen⌠ ma∙ havσ becomσ invalid« Thσ agreemen⌠ become≤ invaliΣ ì afte≥ an∙ conditioε whicΦ ma∙ leavσ thσ datß transfe≥ agreemen⌠ iε aε ì indeterminatσ statσ sucΦ as: áá(1⌐ afte≥ ß harΣ rese⌠ condition áá(2⌐ afte≥ ß BU╙ DEVIC┼ RESE╘ messagσ and áá(3⌐ afte≥ ß powe≥ cycle. .cp 3 ááIε addition¼ aε SCS╔ devicσ ma∙ initiatσ aε SDT╥ messagσ exchangσ wheneve≥ ì i⌠ i≤ appropriatσ t∩ negotiatσ ß ne≈ datß transfe≥ agreemen⌠ (eithe≥ ì synchronou≤ o≥ asynchronous)« SCS╔ device≤ tha⌠ arσ capablσ oµ synchronou≤ ì datß transfer≤ shal∞ no⌠ responΣ t∩ aε SDT╥ messagσ witΦ ß MESSAG┼ REJEC╘ ì message. .lm3 .pm0 .aw1 ááIMPLEMENTOR╙ NOTES: áá(1⌐ Rσ-negotiatioε a⌠ ever∙ selectioε i≤ no⌠ recommended¼ sincσ ß ì áásignifican⌠ performancσ impac⌠ i≤ likely« áá(2⌐ Duσ t∩ historica∞ problem≤ witΦ earl∙ hos⌠ adapter≤ tha⌠ coulΣ no⌠ ì ááaccep⌠ aε SDT╥ message¼ somσ target≤ ma∙ no⌠ initiatσ synchronou≤ ì áánegotiatioε afte≥ ß powe≥ cyclσ a≤ requireΣ b∙ thi≤ standard« Hos⌠ adapter≤ ì áátha⌠ suppor⌠ synchronou≤ modσ ma∙ avoiΣ thσ ensuinτ failurσ mode≤ wheε thσ ì áátarge⌠ i≤ independentl∙ powe≥ cycleΣ b∙ initiatinτ ß synchronou≤ negotiatioε ì ááoε eacΦ REQUES╘ SENS┼ anΣ INQUIR┘ command« Thi≤ approacΦ increase≤ thσ SCS╔ ì áábu≤ overheaΣ anΣ i≤ no⌠ recommendeΣ fo≥ ne≈ implementations« Thσ correc⌠ ì áámethoΣ i≤ t∩ responΣ t∩ aε SDT╥ messagσ witΦ ß MESSAG┼ REJEC╘ messagσ iµ thσ ì ááeithe≥ thσ initiato≥ o≥ targe⌠ device≤ doe≤ no⌠ suppor⌠ synchronou≤ ì áátransfer≤ o≥ doe≤ no⌠ wan⌠ t∩ negotiatσ fo≥ synchronou≤ transfer≤ a⌠ thσ ì áátime« Usinτ thσ correc⌠ methoΣ assure≤ compatibilit∙ witΦ widσ datß ì áátransfer≤ anΣ futurσ enhancements. .lm1 .pm3 .aw1 .cp 3 ááThσ SDT╥ messagσ exchangσ establishe≤ thσ permissiblσ transfe≥ period≤ anΣ ì thσ REQ/AC╦ offset≤ fo≥ al∞ logica∞ unit≤ anΣ targe⌠ routine≤ oε thσ tw∩ ì devices« Thi≤ agreemen⌠ onl∙ applie≤ t∩ datß phases. .cp 3èááThσ transfe≥ perioΣ i≤ thσ minimuφ timσ alloweΣ betweeε leadinτ edge≤ oµ ì successivσ RE╤ pulse≤ anΣ oµ successivσ AC╦ pulse≤ t∩ mee⌠ thσ devicσ ì requirement≤ fo≥ successfu∞ receptioε oµ data. .cp 3 ááThσ REQ/AC╦ offse⌠ i≤ thσ maximuφ numbe≥ oµ RE╤ pulse≤ alloweΣ t∩ bσ ì outstandinτ beforσ thσ leadinτ edgσ oµ it≤ correspondinτ AC╦ pulsσ i≤ receiveΣ ì a⌠ thσ target« Thi≤ valuσ i≤ choseε t∩ preven⌠ overflo≈ condition≤ iε thσ ì device'≤ receptioε buffe≥ anΣ offse⌠ counter« ┴ REQ/AC╦ offse⌠ valuσ oµ zer∩ ì shal∞ indicatσ asynchronou≤ datß transfe≥ mode╗ ß valuσ oµ FFΦ shal∞ indicatσ ì unlimiteΣ REQ/AC╦ offset. .cp 3 ááThσ originatinτ devicσ (thσ devicσ tha⌠ send≤ thσ firs⌠ oµ thσ pai≥ oµ SDT╥ ì messages⌐ set≤ it≤ value≤ accordinτ t∩ thσ rule≤ abovσ t∩ permi⌠ i⌠ t∩ receivσ ì datß successfully« Iµ thσ respondinτ devicσ caε als∩ receivσ datß ì successfull∙ witΦ thesσ value≤ (o≥ smalle≥ transfe≥ period≤ o≥ large≥ REQ/AC╦ ì offset≤ o≥ both)¼ i⌠ return≤ thσ samσ value≤ iε it≤ SDT╥ message« Iµ i⌠ ì require≤ ß large≥ transfe≥ period¼ ß smalle≥ REQ/AC╦ offset¼ o≥ botΦ iε orde≥ ì t∩ receivσ datß successfully¼ i⌠ substitute≤ value≤ iε it≤ SDT╥ messagσ a≤ ì required¼ returninτ unchangeΣ an∙ valuσ no⌠ requireΣ t∩ bσ changed« EacΦ ì devicσ wheε transmittinτ datß shal∞ respec⌠ thσ limit≤ se⌠ b∙ thσ other'≤ SDT╥ ì message¼ bu⌠ i⌠ i≤ permitteΣ t∩ transfe≥ datß witΦ large≥ transfe≥ periods¼ ì smalle≥ REQ/AC╦ offsets¼ o≥ botΦ thaε specifieΣ iε thσ other'≤ SDT╥ message« ì Thσ successfu∞ completioε oµ aε exchangσ oµ SDT╥ message≤ implie≤ aε agreemen⌠ ì a≤ follows: .cp 11 .pm 1 .lm 36 Responding Device SDTR response ImplieΣ Agreement ------------------------------- ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡- (1) Non-zero REQ/ACK offset EacΦ devicσ transmit≤ datß witΦ ß transfe≥ ì áááááááááááááááááááááááááááááááááááperioΣ equa∞ t∩ o≥ greate≥ thaε anΣ ß ì áááááááááááááááááááááááááááááááááááREQ/AC╦ offse⌠ equa∞ t∩ o≥ les≤ thaε thσ ì ááááááááááááááááááááááááááááááááááávalue≤ receiveΣ iε thσ othe≥ device'≤ SDT╥ ì ááááááááááááááááááááááááááááááááááámessage. (2) REQ/ACK offset equal to zero Asynchronou≤ transfer (3) MESSAGE REJECT message Asynchronou≤ transfer .pm 3 .lm 1 ááIµ thσ initiato≥ recognize≤ tha⌠ negotiatioε i≤ required¼ i⌠ assert≤ thσ AT╬ ì signa∞ anΣ send≤ ß SDT╥ messagσ t∩ begiε thσ negotiatinτ process« Afte≥ ì successfull∙ completinτ thσ MESSAG┼ OU╘ phase¼ thσ targe⌠ shal∞ responΣ witΦ ì thσ prope≥ SDT╥ message« Iµ aε abnorma∞ conditioε prevent≤ thσ targe⌠ froφ ì returninτ aε appropriatσ response¼ botΦ device≤ shal∞ g∩ t∩ asynchronou≤ datß ì transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ devices. ááFollowinτ targe⌠ responsσ (1⌐ above¼ thσ implieΣ agreemen⌠ fo≥ synchronou≤ ì operatioε shal∞ bσ considereΣ t∩ bσ negateΣ b∙ botΦ thσ initiato≥ anΣ thσ ì targe⌠ iµ thσ initiato≥ assert≤ thσ AT╬ signa∞ anΣ thσ firs⌠ messagσ ou⌠ i≤ ì eithe≥ MESSAG┼ PARIT┘ ERRO╥ o≥ MESSAG┼ REJECT« Iε thi≤ case¼ botΦ device≤ ì shal∞ g∩ t∩ asynchronou≤ datß transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ ì devices« Fo≥ thσ MESSAG┼ PARIT┘ ERRO╥ case¼ thσ implieΣ agreemen⌠ shal∞ bσ ì reinstateΣ iµ ß rσ-transmitta∞ oµ thσ seconΣ oµ thσ pai≥ oµ message≤ i≤ ì successfull∙ accomplished« Afte≥ ß vendo≥-specifiπ numbe≥ oµ retr∙ attempt≤ ì (greate≥ thaε zero)¼ iµ thσ targe⌠ receive≤ ß MESSAG┼ PARIT┘ ERRO╥ message¼ i⌠ ì shal∞ terminatσ thσ retr∙ activity« Thi≤ ma∙ bσ donσ eithe≥ b∙ changinτ t∩ ì an∙ othe≥ informatioε transfe≥ phasσ anΣ transferrinτ a⌠ leas⌠ onσ bytσ oµ ìèinformatioε o≥ b∙ goinτ t∩ thσ BU╙ FRE┼ phasσ (seσ 5.1.1)« Thσ initiato≥ ì shal∞ accep⌠ sucΦ actioε a≤ abortinτ thσ negotiation¼ anΣ botΦ device≤ shal∞ ì g∩ t∩ asynchronou≤ datß transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ ì devices« ááIµ thσ targe⌠ recognize≤ tha⌠ negotiatioε i≤ required¼ i⌠ send≤ aε SDT╥ ì messagσ t∩ thσ initiator« Prio≥ t∩ releasinτ thσ AC╦ signa∞ oε thσ las⌠ bytσ ì oµ thσ SDT╥ messagσ froφ thσ target¼ thσ initiato≥ shal∞ asser⌠ thσ AT╬ signa∞ ì anΣ responΣ witΦ it≤ SDT╥ messagσ o≥ witΦ ß MESSAG┼ REJEC╘ message« Iµ aε ì abnorma∞ conditioε prevent≤ thσ initiato≥ froφ returninτ aε appropriatσ ì response¼ botΦ device≤ shal∞ g∩ t∩ asynchronou≤ datß transfe≥ modσ fo≥ datß ì transfer≤ betweeε thσ tw∩ devices. ááFollowinτ aε initiator'≤ respondinτ SDT╥ message¼ aε implieΣ agreemen⌠ fo≥ ì synchronou≤ operatioε shal∞ no⌠ bσ considereΣ t∩ exis⌠ unti∞ thσ targe⌠ leave≤ ì thσ MESSAG┼ OU╘ phase¼ indicatinτ tha⌠ thσ targe⌠ ha≤ accepteΣ thσ ì negotiation« Afte≥ ß vendo≥-specifiπ numbe≥ oµ retr∙ attempt≤ (greate≥ thaε ì zero)¼ iµ thσ targe⌠ ha≤ no⌠ receiveΣ thσ initiator'≤ respondinτ SDT╥ message¼ ì i⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ withou⌠ an∙ furthe≥ informatioε transfe≥ ì attemp⌠ (seσ 5.1.1)« Thi≤ indicate≤ tha⌠ ß catastrophiπ erro≥ conditioε ha≤ ì occurred« BotΦ device≤ shal∞ g∩ t∩ asynchronou≤ datß transfe≥ modσ fo≥ datß ì transfer≤ betweeε thσ tw∩ devices. .cp 5 ááIf¼ followinτ aε initiator'≤ respondinτ SDT╥ message¼ thσ targe⌠ shift≤ t∩ ì MESSAG┼ I╬ phasσ anΣ thσ firs⌠ messagσ iε i≤ MESSAG┼ REJECT¼ thσ implieΣ ì agreemen⌠ shal∞ bσ considereΣ t∩ bσ negateΣ anΣ botΦ device≤ shal∞ g∩ t∩ ì asynchronou≤ datß transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ devices. .cp 10 ááThσ implieΣ synchronou≤ agreemen⌠ shal∞ remaiε iε effec⌠ unti∞ ß BU╙ DEVIC┼ ì RESE╘ messagσ i≤ received¼ unti∞ ß harΣ rese⌠ conditioε occurs¼ o≥ unti∞ onσ ì oµ thσ tw∩ SCS╔ device≤ elect≤ t∩ modif∙ thσ agreement« Thσ defaul⌠ datß ì transfe≥ modσ i≤ asynchronou≤ datß transfe≥ mode« Thσ defaul⌠ datß transfe≥ ì modσ i≤ entereΣ a⌠ powe≥ on¼ afte≥ ß BU╙ DEVIC┼ RESE╘ message¼ o≥ afte≥ ß harΣ ì rese⌠ condition. .cp 15 .aw off .pm 0 5.6.22. TERMINAT┼ I/╧ PROCESS .aw on .pm 3 ááThσ TERMINAT┼ I/╧ PROCES╙ messagσ i≤ sen⌠ froφ thσ initiato≥ t∩ thσ targe⌠ ì t∩ advisσ thσ targe⌠ t∩ terminatσ thσ curren⌠ I/╧ proces≤ withou⌠ corruptinτ ì thσ medium« Upoε successfu∞ receip⌠ oµ thi≤ messagσ thσ targe⌠ shal∞ ì terminatσ thσ curren⌠ I/╧ proces≤ a≤ sooε a≤ possiblσ anΣ returε COMMAN─ ì TERMINATE─ status« Thσ sensσ ke∙ shal∞ bσ se⌠ t∩ N╧ SENS┼ anΣ thσ additiona∞ ì sensσ codσ anΣ qualifie≥ shal∞ bσ se⌠ t∩ I/╧ PROCES╙ TERMINATED« Thσ ì TERMINAT┼ I/╧ PROCES╙ messagσ shal∞ no⌠ affec⌠ pendinτ status¼ data¼ anΣ ì command≤ fo≥ othe≥ queueΣ o≥ executinτ I/╧ processes« However¼ continueΣ ì executioε anΣ statu≤ oµ othe≥ I/╧ processe≤ queueΣ fo≥ thσ I_T_° nexu≤ ma∙ bσ ì affecteΣ b∙ thσ queuσ erro≥ recover∙ optioε specifieΣ iε thσ contro∞ modσ pagσ ì (seσ 7.3.3.1). .cp 10èááIµ thσ I/╧ proces≤ tha⌠ i≤ beinτ terminateΣ ha≤ ß datß transfe≥ associateΣ ì witΦ i⌠ (i.e.¼ DAT┴ I╬ o≥ DAT┴ OU╘ phase)¼ thσ valiΣ bi⌠ iε thσ sensσ datß ì shal∞ bσ se⌠ t∩ onσ anΣ thσ informatioε fielΣ shal∞ bσ se⌠ a≤ follows: áá(1⌐ Iµ thσ commanΣ descripto≥ blocδ specifie≤ aε allocatioε lengtΦ o≥ ì paramete≥ lis⌠ lengtΦ iε bytes¼ thσ informatioε fielΣ shal∞ bσ se⌠ t∩ thσ ì differencσ (residue⌐ betweeε thσ transfe≥ lengtΦ anΣ thσ numbe≥ oµ byte≤ ì successfull∙ transferred. áá(2⌐ Iµ thσ commanΣ descripto≥ blocδ specifie≤ ß transfe≥ lengtΦ field¼ thσ ì informatioε fielΣ shal∞ bσ se⌠ a≤ defineΣ iε thσ REQUES╘ SENS┼ commanΣ (seσ ì 7.2.14). .cp 5 ááIµ thσ I/╧ proces≤ beinτ terminateΣ ha≤ n∩ datß transfe≥ associateΣ witΦ i⌠ ì thσ targe⌠ shal∞ se⌠ thσ valiΣ bi⌠ iε thσ sensσ datß t∩ zer∩ anΣ terminatσ thσ ì I/╧ proces≤ witΦ COMMAN─ TERMINATE─ status« Thσ sensσ ke∙ shal∞ bσ se⌠ t∩ N╧ ì SENS┼ anΣ thσ additiona∞ sensσ codσ anΣ qualifie≥ shal∞ bσ se⌠ t∩ I/╧ PROCES╙ ì TERMINATED. .cp 3 ááWheε an∙ erro≥ conditioε i≤ detecteΣ fo≥ aε I/╧ proces≤ thσ targe⌠ shal∞ ì ignorσ thσ TERMINAT┼ I/╧ PROCES╙ messagσ anΣ terminatσ thσ I/╧ proces≤ witΦ ì thσ appropriatσ erro≥ statu≤ anΣ sensσ datß fo≥ thσ erro≥ condition. .cp 3 ááIµ thσ targe⌠ complete≤ al∞ processinτ fo≥ ß commanΣ (i.e.¼ al∞ datß ha≤ ì beeε read¼ written¼ o≥ processed⌐ anΣ ß TERMINAT┼ I/╧ PROCES╙ messagσ i≤ ì receiveΣ beforσ thσ I/╧ proces≤ i≤ terminated¼ thσ targe⌠ shal∞ ignorσ thσ ì TERMINAT┼ I/╧ PROCES╙ messagσ anΣ terminatσ thσ I/╧ proces≤ iε thσ norma∞ ì manner. .cp 7 ááIµ thσ targe⌠ receive≤ ß TERMINAT┼ I/╧ PROCES╙ messagσ beforσ thσ commanΣ ì descripto≥ blocδ i≤ transferreΣ (i.e.¼ beforσ thσ COMMAN─ phase⌐ o≥ thσ ì messagσ i≤ issueΣ t∩ aε I_T_° nexu≤ tha⌠ doe≤ no⌠ havσ aε activσ o≥ queueΣ I/╧ ì process¼ thσ targe⌠ shal∞ se⌠ thσ valiΣ bi⌠ iε thσ sensσ datß t∩ zer∩ anΣ ì terminatσ thσ I/╧ proces≤ witΦ COMMAN─ TERMINATE─ status« Thσ sensσ ke∙ shal∞ ì bσ se⌠ t∩ N╧ SENS┼ anΣ thσ additiona∞ sensσ codσ anΣ qualifie≥ shal∞ bσ se⌠ t∩ ì I/╧ PROCES╙ TERMINATED. .cp 8 ááIµ thσ curren⌠ I/╧ proces≤ i≤ iε thσ commanΣ queuσ (I_T_° nexu≤ fo≥ untaggeΣ ì queuinτ o≥ I_T_L_╤ nexu≤ fo≥ taggeΣ queuing⌐ anΣ ha≤ no⌠ starteΣ execution¼ ì thσ targe⌠ shal∞ eithe≥ terminatσ thσ I/╧ proces≤ immediatel∙ o≥ disconnec⌠ ì anΣ wai⌠ unti∞ thσ commanΣ i≤ a⌠ thσ heaΣ oµ thσ queuσ (starteΣ executing⌐ ì theε terminatσ thσ I/╧ process« Iε eithe≥ case¼ thσ targe⌠ shal∞ terminatσ ì thσ I/╧ proces≤ witΦ COMMAN─ TERMINATE─ status« Thσ sensσ ke∙ shal∞ bσ se⌠ t∩ ì N╧ SENS┼ anΣ thσ additiona∞ sensσ codσ anΣ qualifie≥ shal∞ bσ se⌠ t∩ I/╧ ì PROCES╙ TERMINATED« Thσ valiΣ bi⌠ shal∞ bσ se⌠ t∩ zero. ááIµ thσ targe⌠ doe≤ no⌠ suppor⌠ thi≤ messagσ o≥ i≤ unablσ t∩ sto≡ thσ curren⌠ ì I/╧ proces≤ fo≥ thσ I_T_° nexus¼ i⌠ shal∞ responΣ b∙ sendinτ ß MESSAG┼ REJEC╘ ì messagσ t∩ thσ initiato≥ anΣ continuinτ thσ I/╧ proces≤ iε ß norma∞ manner. .pm 0 .lm 3 ááIMPLEMENTOR╙ NOTE║ Thσ TERMINAT┼ I/╧ PROCES╙ messagσ provide≤ ß mean≤ fo≥ ì ááthσ initiato≥ t∩ reques⌠ thσ targe⌠ t∩ reducσ thσ transfe≥ lengtΦ oµ thσ ì áácurren⌠ commanΣ t∩ thσ amoun⌠ tha⌠ ha≤ alread∙ beeε transferred« Thσ ì ááinitiato≥ caε usσ thσ sensσ datß t∩ determinσ thσ actua∞ numbe≥ oµ byte≤ o≥ ì ááblock≤ tha⌠ havσ beeε transferred« Thi≤ messagσ i≤ normall∙ useΣ b∙ thσ ì ááinitiato≥ t∩ sto≡ ß length∙ read¼ write¼ o≥ verif∙ operatioε wheε ß highe≥-ì áápriorit∙ commanΣ i≤ availablσ t∩ bσ executed« I⌠ i≤ u≡ t∩ thσ initiato≥ t∩ ìèáácompletσ thσ terminateΣ commanΣ a⌠ ß late≥ time¼ iµ required. .pm 3 .lm 1 .cp 20 .aw off .pm 0 5.6.23. WIDE DATA TRANSFER REQUEST Messagσ Table 5-10: WIDE DATA TRANSFER MESSAGE ============================================================================== Byte | Value | Description | ============================================================================== 0 | 01h | Extended message | -----|---------|-------------------------------------------------------------| 1 | 02h | Extended message length | -----|---------|-------------------------------------------------------------| 2 | 03h | WIDE DATA TRANSFER REQUEST code | -----|---------|-------------------------------------------------------------| 3 | m | Transfer Width (2**m bytes) | ============================================================================== .aw on .pm 3 .cp 9 áá┴ WID┼ DAT┴ TRANSFE╥ REQUES╘ (WDTR⌐ messagσ (Tablσ ╡-10⌐ exchangσ shal∞ bσ ì initiateΣ b∙ aε SCS╔ devicσ wheneve≥ ß previousl∙-arrangeΣ transfe≥ widtΦ ì agreemen⌠ ma∙ havσ becomσ invalid« Thσ agreemen⌠ become≤ invaliΣ afte≥ an∙ ì conditioε whicΦ ma∙ leavσ thσ datß transfe≥ agreemen⌠ iε aε indeterminatσ ì statσ sucΦ as: áá(1⌐ afte≥ ß harΣ rese⌠ condition áá(2⌐ afte≥ ß BU╙ DEVIC┼ RESE╘ messagσ and áá(3⌐ afte≥ ß powe≥ cycle. .cp 5 ááIε addition¼ aε SCS╔ devicσ ma∙ initiatσ aε WDT╥ messagσ exchangσ wheneve≥ ì i⌠ i≤ appropriatσ t∩ negotiatσ ß ne≈ transfe≥ widtΦ agreement« SCS╔ device≤ ì tha⌠ arσ capablσ oµ widσ datß transfer≤ (greate≥ thaε eigh⌠ bits⌐ shal∞ no⌠ ì responΣ t∩ aε WDT╥ messagσ witΦ ß MESSAG┼ REJEC╘ message. .lm3 .pm0 .aw1 ááIMPLEMENTOR╙ NOTE║ Rσ-negotiatioε a⌠ ever∙ selectioε i≤ no⌠ recommended¼ ì áásincσ ß significan⌠ performancσ impac⌠ i≤ likely« .lm1 .pm3 .aw1 .cp 5 ááThσ WDT╥ messagσ exchangσ establishe≤ aε agreemen⌠ betweeε tw∩ SCS╔ device≤ ì oε thσ widtΦ oµ thσ datß patΦ t∩ bσ useΣ fo≥ DAT┴ phasσ transfer≤ betweeε thσ ì tw∩ devices« Thi≤ agreemen⌠ applie≤ t∩ DAT┴ I╬ anΣ DAT┴ OU╘ phase≤ only« Al∞ ì othe≥ informatioε transfe≥ phase≤ shal∞ usσ aε eigh⌠-bi⌠ datß path. .cp 5 ááIµ aε SCS╔ devicσ implement≤ botΦ widσ datß transfe≥ optioε anΣ synchronou≤ ì datß transfe≥ option¼ theε i⌠ shal∞ negotiatσ thσ widσ datß transfe≥ agreemen⌠ ì prio≥ t∩ negotiatinτ thσ synchronou≤ datß transfe≥ agreement« Iµ ß ì synchronou≤ datß transfe≥ agreemen⌠ i≤ iε effect¼ theε aε SCS╔ devicσ tha⌠ ì accept≤ ß WDT╥ messagσ shal∞ rese⌠ thσ synchronou≤ agreemen⌠ t∩ asynchronou≤ ì mode. .cp 3 ááThσ transfe≥ widtΦ tha⌠ i≤ establisheΣ applie≤ t∩ al∞ logica∞ unit≤ oε botΦ ì SCS╔ devices« ValiΣ transfe≥ width≤ arσ ╕ bit≤ (m=00h)¼ 1╢ bit≤ (m=01h)¼ ì anΣ 3▓ bit≤ (m=02h)« Value≤ oµ φ greate≥ thaε 02Φ arσ reserved. .cp 7èááThσ originatinτ SCS╔ devicσ (thσ SCS╔ devicσ tha⌠ send≤ thσ firs⌠ oµ thσ ì pai≥ oµ WDT╥ messages⌐ set≤ it≤ transfe≥ widtΦ valuσ t∩ thσ maximuφ datß patΦ ì widtΦ i⌠ elect≤ t∩ accommodate« Iµ thσ respondinτ SCS╔ devicσ caε als∩ ì accommodatσ thi≤ transfe≥ width¼ i⌠ return≤ thσ samσ valuσ iε it≤ WDT╥ ì message« Iµ i⌠ require≤ ß smalle≥ transfe≥ width¼ i⌠ substitute≤ thσ smalle≥ ì valuσ iε it≤ WDT╥ message« Thσ successfu∞ completioε oµ aε exchangσ oµ WDT╥ ì message≤ implie≤ aε agreemen⌠ a≤ follows: .cp 11 .pm 1 .lm 36 Responding Device WDTR Response ImplieΣ Agreement -------------------------------- ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡- (1) Non-zero transfer width EacΦ devicσ transmit≤ anΣ receive≤ datß ì áááááááááááááááááááááááááááááááááááwitΦ ß transfe≥ widtΦ equa∞ t∩ thσ ì ááááááááááááááááááááááááááááááááááárespondinτ SCS╔ device'≤ transfe≥ width. (2) Transfer width equal to zero Eigh⌠-bi⌠ Datß Transfer (3) MESSAGE REJECT message Eigh⌠-bi⌠ Datß Transfer .pm 3 .lm 1 .cp 5 ááIµ thσ initiato≥ recognize≤ tha⌠ negotiatioε i≤ required¼ i⌠ assert≤ thσ AT╬ ì signa∞ anΣ send≤ ß WDT╥ messagσ t∩ begiε thσ negotiatinτ process« Afte≥ ì successfull∙ completinτ thσ MESSAG┼ OU╘ phase¼ thσ targe⌠ shal∞ responΣ witΦ ì thσ prope≥ WDT╥ message« Iµ aε abnorma∞ conditioε prevent≤ thσ targe⌠ froφ ì returninτ aε appropriatσ response¼ botΦ device≤ shal∞ g∩ t∩ eigh⌠-bi⌠ datß ì transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ devices. .cp 14 ááFollowinτ targe⌠ responsσ (1⌐ above¼ thσ implieΣ agreemen⌠ fo≥ widσ datß ì transfer≤ shal∞ bσ considereΣ t∩ bσ negateΣ b∙ botΦ thσ initiato≥ anΣ thσ ì targe⌠ iµ thσ initiato≥ assert≤ AT╬ anΣ thσ firs⌠ messagσ ou⌠ i≤ eithe≥ ì MESSAG┼ PARIT┘ ERRO╥ o≥ MESSAG┼ REJECT« Iε thi≤ case¼ botΦ device≤ shal∞ g∩ ì t∩ eigh⌠-bi⌠ datß transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ devices« ì Fo≥ thσ MESSAG┼ PARIT┘ ERRO╥ case¼ thσ implieΣ agreemen⌠ shal∞ bσ reinstateΣ ì iµ ß rσ-transmitta∞ oµ thσ seconΣ oµ thσ pai≥ oµ message≤ i≤ successfull∙ ì accomplished« Afte≥ ß vendo≥-specifiπ numbe≥ oµ retr∙ attempt≤ (greate≥ thaε ì zero)¼ iµ thσ targe⌠ receive≤ ß MESSAG┼ PARIT┘ ERRO╥ message¼ i⌠ shal∞ ì terminatσ thσ retr∙ activity« Thi≤ ma∙ bσ donσ eithe≥ b∙ changinτ t∩ an∙ ì othe≥ informatioε transfe≥ phasσ anΣ transferrinτ a⌠ leas⌠ onσ bytσ oµ ì informatioε o≥ b∙ goinτ t∩ thσ BU╙ FRE┼ phasσ (seσ 5.1.1)« Thσ initiato≥ ì shal∞ accep⌠ sucΦ actioε a≤ abortinτ thσ negotiation¼ anΣ botΦ device≤ shal∞ ì g∩ t∩ eigh⌠-bi⌠ datß transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ devices« .cp 5 ááIµ thσ targe⌠ recognize≤ tha⌠ negotiatioε i≤ required¼ i⌠ send≤ ß WDT╥ ì messagσ t∩ thσ initiator« Prio≥ t∩ releasinτ thσ AC╦ signa∞ oε thσ las⌠ bytσ ì oµ thσ WDT╥ messagσ froφ thσ target¼ thσ initiato≥ shal∞ asser⌠ thσ AT╬ signa∞ ì anΣ responΣ witΦ it≤ WDT╥ messagσ o≥ witΦ ß MESSAG┼ REJEC╘ message« Iµ aε ì abnorma∞ conditioε prevent≤ thσ initiato≥ froφ returninτ aε appropriatσ ì response¼ botΦ device≤ shal∞ g∩ t∩ eigh⌠-bi⌠ datß transfe≥ modσ fo≥ datß ì transfer≤ betweeε thσ tw∩ devices. .cp 10èááFollowinτ aε initiator'≤ respondinτ WDT╥ message¼ aε implieΣ agreemen⌠ fo≥ ì widσ datß transfe≥ operatioε shal∞ no⌠ bσ considereΣ t∩ exis⌠ unti∞ thσ targe⌠ ì leave≤ thσ MESSAG┼ OU╘ phase¼ indicatinτ tha⌠ thσ targe⌠ ha≤ accepteΣ thσ ì negotiation« Afte≥ ß vendo≥-specifiπ numbe≥ oµ retr∙ attempt≤ (greate≥ thaε ì zero)¼ iµ thσ targe⌠ ha≤ no⌠ receiveΣ thσ initiator'≤ respondinτ WDT╥ message¼ ì i⌠ shal∞ g∩ t∩ thσ BU╙ FRE┼ phasσ withou⌠ an∙ furthe≥ informatioε transfe≥ ì attemp⌠ (seσ 5.1.1)« Thi≤ indicate≤ tha⌠ ß catastrophiπ erro≥ conditioε ha≤ ì occurred« BotΦ device≤ shal∞ g∩ t∩ eigh⌠-bi⌠ datß transfe≥ modσ fo≥ datß ì transfer≤ betweeε thσ tw∩ devices. .cp 5 ááIf¼ followinτ aε initiator'≤ respondinτ WDT╥ message¼ thσ targe⌠ shift≤ t∩ ì MESSAG┼ I╬ phasσ anΣ thσ firs⌠ messagσ iε i≤ MESSAG┼ REJECT¼ thσ implieΣ ì agreemen⌠ shal∞ bσ considereΣ t∩ bσ negateΣ anΣ botΦ device≤ shal∞ g∩ t∩ ì eigh⌠-bi⌠ datß transfe≥ modσ fo≥ datß transfer≤ betweeε thσ tw∩ devices. .cp 6 ááThσ implieΣ transfe≥ widtΦ agreemen⌠ shal∞ remaiε iε effec⌠ unti∞ ß BU╙ ì DEVIC┼ RESE╘ messagσ i≤ received¼ unti∞ ß harΣ rese⌠ conditioε occurs¼ o≥ ì unti∞ onσ oµ thσ tw∩ SCS╔ device≤ elect≤ t∩ modif∙ thσ agreement« Thσ defaul⌠ ì datß transfe≥ widtΦ i≤ eigh⌠-bi⌠ datß transfe≥ mode« Thσ defaul⌠ datß ì transfe≥ modσ i≤ entereΣ a⌠ powe≥ on¼ afte≥ ß BU╙ DEVIC┼ RESE╘ message¼ o≥ ì afte≥ ß harΣ rese⌠ condition. ..end of section .paè áá (Thi≤ pagσ i≤ intentionall∙ blank.) .paè