 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] D. MENG            ]    PASS PROGRAM NOTE        ]        63682 *   ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  07/21/86  ]
 ] SSOAS/(281)335-2226]      RELEASE NOTE( )        ] REV C: 04/09/97  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI-26B AND SUBS               ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW (X)  GNC ( )  VU ( )  SM/PL ( )] 0, G1, G2, G3, G6, G8, G9, S2,  ]
 ]                                   ] S4, P9                          ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: I/O, COMMFAULTS                                  ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: SBIO                                           ]
 ]_____________________________________________________________________]
 ] TITLE:   I/O ERRORS MAY REPEAT THREE OR MORE TIMES BEFORE BYPASS    ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:   * REFERENCE DR 035211                                ]
 ]  THIS I/O ERROR/BYPASS SIGNATURE MAY OCCUR IN THE FOLLOWING         ]
 ]    CONDITIONS:                                                      ]
 ]                                                                     ]
 ]1)IF THE I/O COMPLETION FOR A LOW PRIORITY COMMFAULTABLE TRANSACTION ]
 ]  IS INTERRUPTED ON AN ERROR CYCLE BY A TIMER TO INITIATE HIGHER     ]
 ]  PRIORITY I/O, THE LOW PRIORITY TRANSACTION MAY NOT BE ABLE TO      ]
 ]  PERFORM BYPASS PROCESSING ON THIS CYCLE.  THIS WOULD OCCUR ONLY IF ]
 ]  THE HIGHER PRIORITY I/O TRANSACTION ALSO COMPLETED WITH AN ERROR   ]
 ]  (ON A DIFFERENT DATA BUS) ON THIS CYCLE.                           ]
 ]                                                                     ]
 ]  THE ONLY CASE OF THIS EVER OBSERVED INVOLVED THE LOW PRIORITY SRB  ]
 ]  INPUT TRANSACTION AND THE HFE INPUT TRANSACTION WITH SIMULTANEOUS  ]
 ]  ERRORS ON LDB1 AND A FLIGHT CRITICAL DATA BUS.  IN THIS CASE, ONE  ]
 ]  EXTRA CYCLE WAS REQUIRED TO BYPASS ALL ELEMENTS IN THE SRB INPUT   ]
 ]  I/O TRANSACTION.                                                   ]
 ]                                                                     ]
 ]2)THIS PHENOMENON MAY ALSO BE OBSERVED WHEN A BUS RECONFIGURATION OPS]
 ]  MODE RECALL IS PERFORMED.  AS EACH STRING IS RE-CONFIGURED THE BCE ]
 ]  ELEMENTS ARE RESTORED AND THE TRANSACTION (E.G. HFE, MFE, ETC.)    ]
 ]  ERROR COUNTERS ARE RESET TO 0.  THE RECONFIGURATION OF ALL STRINGS ]
 ]  MAY TAKE SEVERAL MINOR CYCLES.  THEREFORE, 2 OR MORE I/O ERRORS    ]
 ]  MAY OCCUR ON ONE OR MORE BUSSES BEFORE A FAILED OR POWERED OFF BTU/]
 ]                                                                     ]
 ]                - CONTINUED ON SUPPLEMENT PAGE -                     ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]  NONE                                                               ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]SSOAS:  JOHN MAGLEY       DATE 04/15/97]                             ]
 ]    --------------------      ---------]                             ]
 ]ASD:  ERIC C. BINGHAM     DATE 04/15/97]                             ]
 ]    --------------------      ---------] MELVIN R. ROTHER   06/06/97 ]
 ]PF MGR:  KAYLENE KINDT    DATE 04/16/97]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
 @




 +_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] DR:              ]
 ] D. MENG            ]    PASS PROGRAM NOTE        ]        63682     ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  07/21/86  ]
 ] SSOAS/(281)335-2226]      RELEASE NOTE( )        ] REV C: 04/09/97  ]
 ]____________________]_____________________________]__________________]
 ] TITLE:                                                              ]
 ]          I/O ERRORS MAY REPEAT THREE OR MORE TIMES BEFORE BYPASS    ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]  LRU IS BYPASSED.  THE TOTAL NUMBER OF ERRORS LOGGED IS INDETERMI-  ]
 ]  NATE, I.E. DEPENDENT ON THE NUMBER OF FAILED OR POWERED OFF BTU'S/ ]
 ]  LRU'S AND TIMING OF BUS RECONFIGURATION WITH RESPECT TO THE I/O    ]
 ]  TRANSACTION(S) ENCOUNTERING AN ERROR.                              ]
 ]                                                                     ]
 ]3)AFTER AN I/O RESET, THREE OR MORE I/O ERRORS MAY BE LOGGED ON AN   ]
 ]  ELEMENT OF BYPASSABLE I/O TRANSACTIONS WHICH ARE PERFORMED EVERY   ]
 ]  960 MS (E.G.GPS,MTU,G9 PF LOW RATE) BEFORE THE ELEMENT IS BYPASSED.]
 ]  AN I/O RESET PROCESSES ONE FC/PL STRING AND/OR LDB BUS EVERY 960   ]
 ]  MS.  AS EACH STRING/BUS IS PROCESSED, THE ELEMENTS FOR THAT STRING/]
 ]  BUS ARE RESTORED AND THE TRANSACTION ERROR COUNTERS (TEC) FOR ALL  ]
 ]  TRANSACTIONS (DEVICE IDS) ARE RESET TO ZERO. THEREFORE, ANY 1.04 HZ]
 ]  TRANSACTION WHICH ENCOUNTERS AN ERROR WILL INCREMENT ITS TEC TO ONE]
 ]  THEN HAVE ITS TEC RESET TO ZERO AS EACH SUCCEEDING STRING (FC/PL)  ]
 ]  OR LDB IS PROCESSED.  THUS THE TEC FOR 1.04 HZ I/O TRANSACTIONS    ]
 ]  WILL NOT BE INCREMENTED TO TWO AND THE ELEMENT READ WILL NOT BE    ]
 ]  BYPASSED UNTIL AFTER THE LAST STRING OR BUS IF PROCESSED.          ]
 ]                                                                     ]
 ]  THIS PROCESSING IS ONLY PERFORMED FOR STRINGS OR BUSES ASSIGNED TO ]
 ]  THE GPC OR GPC(S) IN THE RS. THEREFORE, THE NUMBER OF ERRORS LOGGED]
 ]  PRIOR TO BYPASS OF THE ELEMENT(S) DEPENDS ON WHICH STRING OR BUS   ]
 ]  THE ELEMENT IS ON AND THE NUMBER OF STRINGS OR BUSES ASSIGNED TO   ]
 ]  THE GPC OR GPC(S) IN THE RS.  FOR EXAMPLE: ON GPS FLIGHT I/O. IF   ]
 ]  THE GPS 2 RECEIVER IS FAILED OR POWERED OFF AND AN I/O RESET IS    ]
 ]  PERFORMED, FOUR GPS 2 I/O ERRORS WOULD BE LOGGED (STARTING WITH THE]
 ]  FC STRING 2 RESET PROCESSING) PRIOR TO BYPASS OF THE ELEMENT IF THE]
 ]  PL AND LDB(S) WERE "NOT" ASSIGNED TO THE GPC(S).  IF ALL STRINGS   ]
 ]  (FC/PL) AND LDB(S) WERE ASSIGNED, SEVEN GPS 2 I/O ERRORS WOULD BE  ]
 ]  LOGGED PRIOR TO BYPASS.                                            ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 @
