 + ____________________________________________________________________
 ] AUTHOR:            ]                             ]                  ]
 ] R J CMELAK         ]    BFS PROGRAM NOTE         ] SMS: B05284A     ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  9/26/80   ]
 ] BNA 922-5246       ]      RELEASE NOTE ( )       ] REV B 11/19/97   ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ]  OI-26B & SUBS                ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]           MAJOR SOFTWARE AREA:            ] OPS MODES AFFECTED:     ]
 ]BSL( ) BSS(X) GNC( ) SEQ( ) SM/SP( ) IPL( )]  0, 1, 3, 6             ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: I/O, BCE                                         ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: MG038101/3.1.9.3                               ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ]  STRING DOWNMODE DUE TO I/O ERROR DURING I/O RESET                  ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]  IT SHOULD BE NOTED THAT THE PORT MODE, THE OPS MODE RECALL, AND    ]
 ]  THE PASS I/O RESET WITH AN LRU FAILURE HAVE A SIMILAR STRING       ]
 ]  DOWNMODE BEHAVIOR IN BFS.                                          ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                          (CONTINUED ON PAGE 2)      ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ]                                                                     ]
 ]  ENTER A BFS I/O RESET WHEN BFS DOWNMODES A STRING FOR ANY OF       ]
 ]  THE FOLLOWING REASONS:                                             ]
 ]                                                                     ]
 ]    1) OCCURRENCE OF LRU FAILURE DURING PASS ENTERED I/O RESET.      ]
 ]                                                                     ]
 ]    2) PREVIOUS MTU OR GPS FAILURE WITH PASS ENTERED I/O RESET -     ]
 ]       ALLOW TEN SECONDS TO ELAPSE AFTER THE PASS I/O RESET.         ]
 ]                                                                     ]
 ]    3) OPS MODE RECALL WITH PREVIOUS LRU FAILURE.                    ]
 ]                                                                     ]
 ]    4) PORT MODE.                                                    ]
 ]                                                                     ]
 ]  REFER TO PASS USER NOTE 35211.                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]BNA:<S> D. CORBIN         DATE 12/04/97]                             ]
 ]    --------------------      ---------]                             ]
 ]ASD:   ERIC C. BINGHAM    DATE 02/24/98]                             ]
 ]    --------------------      ---------] DARRELL E. STAMPER 02/24/98 ]
 ]PF MGR:  M. C. KERR       DATE 02/23/98]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_____________________________________________________________________]
 @




 +_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ]                  ]
 ] R J CMELAK         ]    BFS PROGRAM NOTE         ] SMS: B05284A     ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  9/26/80   ]
 ] BNA/922-5246       ]      RELEASE NOTE ( )       ] REV B 11/19/97   ]
 ]____________________]_____________________________]__________________]
 ] TITLE:                                                              ]
 ]                                                                     ]
 ]   STRING DOWNMODE DUE TO I/O ERROR DURING I/O RESET                 ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]  IF AN LRU FAILS JUST PRIOR TO OR DURING A PASS I/O RESET SUCH      ]
 ]  THAT BOTH PASS AND BFS COUNT ONE ERROR BEFORE PASS RESETS ITS      ]
 ]  ERROR COUNTERS (BECAUSE OF THE I/O RESET) BFS WILL COUNT TWO       ]
 ]  ERRORS AND BYPASS THE ELEMENT BEFORE PASS DOES. BFS WILL THEN      ]
 ]  DOWNMODE THE STRING ASSOCIATED WITH THE FAILED ELEMENT DUE TO      ]
 ]  TRANSFER DATA ELEMENT BYPASS DISCREPANCY. 'JUST PRIOR TO' IS       ]
 ]  DEFINED AS UP TO ONE MINOR CYCLE FOR HIGH FREQUENCY INPUTS.        ]
 ]                                                                     ]
 ]  AN OPS MODE RECALL BUS RECONFIGURATION CONTAINS AN EMBEDDED I/O    ]
 ]  RESET WHICH CAN CAUSE BFS TO DOWNMODE THE STRING WHICH CONTAINS    ]
 ]  A FAULTY LRU. THIS I/O RESET IS MORE RAPID THAN NORMAL BUT CAN     ]
 ]  CAUSE A TRANSFER ELEMENT BYPASS AND SUBSEQUENT STRING DOWNMODE     ]
 ]  JUST AS PREVIOUSLY DESCRIBED.                                      ]
 ]                                                                     ]
 ]  THE COMBINATION OF NOMINAL I/O RESET PROCESSING TIMING AND A       ]
 ]  PREVIOUS FAILURE ON A LOW FREQUENCY READ SUCH AS AN MTU OR GPS CAN ]
 ]  CAUSE AN ELEMENT DISCREPANCY BETWEEN PASS AND BFS WITH A SUB-      ]
 ]  SEQUENT STRING DOWNMODE. HERE, TO RECOVER THE STRING, A BFS        ]
 ]  ENTERED I/O RESET MUST FOLLOW THE PASS I/O RESET BY AT LEAST       ]
 ]  TEN SECONDS.                                                       ]
 ]                                                                     ]
 ]  A PORT MODE BUS RECONFIGURATION CAUSES BFS TO DOWNMODE THE         ]
 ]  STRING BECAUSE BFS IS UNAWARE OF THE CHANGE IN BUS ASSIGNMENTS.    ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 @
