 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] CHUCK WOHL         ]    PASS PROGRAM NOTE        ]       37590      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] LSIS/282-7396      ]      RELEASE NOTE( )        ] REV A: 08/24/95  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] REL 18 AND SUBS               ]  CREW (X)  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:  DEU, FTS                                        ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: SDEU, SBIO                                     ]
 ]_____________________________________________________________________]
 ] TITLE:  DUAL COMMANDERS CAN CAUSE FAIL TO SYNC (FTS)                ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] THE FOLLOWING ARE SOME OF THE RECOGNIZED CAUSES FOR DUAL COMMANDERS ]
 ] ON AN ORBITER DATA BUS:                                             ]
 ]   1) DUAL DEU COMMANDERS WILL RESULT IF A DEU COMMANDED BY          ]
 ]      A GPC OUTSIDE THE COMMON SET (CS) (E.G. A GPC WHICH HAS        ]
 ]      PREVIOUSLY FTS) IS ACQUIRED BY THE CS VIA A GPC/CRT KEY        ]
 ]      ENTRY.  THIS WILL ALSO OCCUR IF A GPC/CRT INPUT IS PERFORMED   ]
 ]      ON A BFS CONTROLLED CRT TO ASSIGN ANOTHER CRT TO BFS WHICH IS  ]
 ]      CURRENTLY CONTROLLED BY A PASS GPC. (NOTE: THE BFS WILL HONOR  ]
 ]      PASS GPC/CRT INPUTS, BUT THE PASS DOES NOT LISTEN AND WILL     ]
 ]      NOT HONOR BFS GPC/CRT INPUTS.)                                 ]
 ]                                                                     ]
 ]   2) DUAL COMMANDERS MAY RESULT IF A BUS IS MANUALLY ASSIGNED       ]
 ]      TO MULTIPLE GPCS EXECUTING IN DIFFERENT MEMORY CONFIGURATIONS. ]
 ]                                                                     ]
 ]   3) DUAL COMMANDERS MAY RESULT IF A BUS COMMANDED BY A GPC         ]
 ]      OUTSIDE THE CS/RS (E.G. A GPC WHICH HAS PREVIOUSLY FTS         ]
 ]      AND NOT POWERED OFF OR MODED TO HALT) IS ASSIGNED TO A NEW     ]
 ]      GPC VIA AN OPS MODE RECALL OR OPS TRANSITION.                  ]
 ]                                                                     ]
 ]   4) DUAL COMMANDERS MAY RESULT FROM THE FAILURE OF ONE OR MORE     ]
 ]      HARDWARE DISCRETES WHICH ALLOWS BFS OR PASS TO ASSUME          ]
 ]                                                                     ]
 ]                                                                     ]
 ]             - CONTINUED ON SUPPLEMENT PAGE -                        ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]LSIS:  JEAN L. ZOPHY      DATE 10/18/95]                             ]
 ]    --------------------      ---------]                             ]
 ]ASD:  ERIC C. BINGHAM     DATE 10/19/95]                             ]
 ]    --------------------      ---------] DARRELL E. STAMPER 10/23/95 ]
 ]PF MGR: KAYLENE F. KINDT  DATE 10/20/95]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
 @



 +_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] DR:              ]
 ] CHUCK WOHL         ]    PASS PROGRAM NOTE        ]       37590      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] LSIS/282-7396      ]      RELEASE NOTE( )        ] REV A: 08/24/95  ]
 ]____________________]_____________________________]__________________]
 ] TITLE:  DUAL COMMANDERS CAN CAUSE FAIL TO SYNC (FTS)                ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]      COMMAND OR FAIL TO RELINQUISH CONTROL OF A BUS WHICH IS        ]
 ]      COMMANDED BY ANOTHER GPC.  FOR EXAMPLE: PASS GPCS IN           ]
 ]      CONTROL OF CRTS 1 & 2 AND BFS IN CONTROL OF CRT 3 BASED        ]
 ]      ON DI'S 38 & 39 = 11 IN ALL GPCS.  IF DI 38 FAILS OFF IN       ]
 ]      THE BFS GPC ONLY, BFS WILL ASSUME COMMAND OF THE CRT 1 BUS     ]
 ]      AND BECOME A DUAL COMMANDER ON THE BUS ALONG WITH THE PASS     ]
 ]      GPC IN COMMAND OF THE BUS.                                     ]
 ]                                                                     ]
 ] THE FOLLOWING ARE SOME MANIFESTATIONS/RESULTS OF DUAL BUS           ]
 ] COMMANDERS:                                                         ]
 ]                                                                     ]
 ]   1) MULTIPLE I/O ERRORS WITH DIFFERENT SIGNATURES; FOR             ]
 ]      EXAMPLE: INITIAL TIMEOUT, INTERWORD TIMEOUT, COMMAND SYNC,     ]
 ]      IUA MISMATCH, SEV BIT ERRORS, TRANSMITTER DISABLED/MIA         ]
 ]      BUSY, ETC.                                                     ]
 ]                                                                     ]
 ]   2) BCE OR BTU SEGMENT BYPASSES AND FAULT MESSAGES DUE TO          ]
 ]      BYPASSES OR COMMFAULTS.                                        ]
 ]                                                                     ]
 ]   3) I/O ERROR CRT MESSAGE(S) AND SYMPTOMS OR EVIDENCE OF TWO       ]
 ]      SEPARATE DISPLAYS (E.G. PASS AND BFS) BEING OUTPUT TO THE      ]
 ]      SAME CRT.                                                      ]
 ]                                                                     ]
 ]   4) A REDUNDANT SET GPC "MAY" FAIL TO SYNC DUE TO NON-UNIVERSAL    ]
 ]      I/O ERROR PROCESSING.  THIS COULD CAUSE RS BREAKUP.            ]
 ]                                                                     ]
 ]   5) RS GPCS MAY FAIL INDIVIDUALLY OR SPLIT (2 VS 2) BASED          ]
 ]      ON MIXED PERCEPTION DEU INPUT ERRORS AND THEIR SUBSEQUENT      ]
 ]      RESPONSE TO THEM (E.G. INTERPRETATION OF BFS TIME FILL DATA    ]
 ]      AS A MESSAGE HEADER WORD WITH THE DEU IPL REQUEST BIT, ON      ]
 ]      OR OFF).                                                       ]
 ]                                                                     ]
 ]   NOTE: REFERENCE 4 & 5.  ONE OR MORE RS GPC(S) MAY FTS IN LESS THAN]
 ]         A SECOND OR WITHIN SECONDS OF THE TIME DUAL COMMANDS BEGIN. ]
 ]                                                                     ]
 ]   6) IMU ERROR INDICATIONS DUE TO DUAL TORQUEING COMMANDS FROM      ]
 ]      PASS AND BFS                                                   ]
 ]                                                                     ]
 ]   7) MDM, MEC, AND/OR EIU "FUNNIES" BASED ON RECEIVING DUAL         ]
 ]      COMMANDS                                                       ]
 ]                                                                     ]
 ]                - CONTINUED ON SUPPLEMENT PAGE -                     ]
 ]_____________________________________________________________________]
 @




 +_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] DR:              ]
 ] CHUCK WOHL         ]    PASS PROGRAM NOTE        ]       37590      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] LSIS/282-7396      ]      RELEASE NOTE( )        ] REV A: 08/24/95  ]
 ]____________________]_____________________________]__________________]
 ]                                                                     ]
 ] TITLE:  DUAL COMMANDERS CAN CAUSE FAIL TO SYNC (FTS)                ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ]   8) IN THE CASE OF 2 VS 2 RS SPLIT, A GPC IN EACH RS OUTPUTS       ]
 ]      DOWNLIST DATA TO THE PCMMU.  THIS WILL CAUSE SCRAMBLING        ]
 ]      AND/OR INTERMITTENT LOSS OF D/L DATA.                          ]
 ]                                                                     ]
 ] REFERENCE DR038458 AND DR100718                                     ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]                                                                     ]
 ] THE BFC CRT SEL SWITCH SHOULD BE USED FOR DEU TRANSFERS BETWEEN BFS ]
 ] AND PASS.  THE MAJ FUNC SWITCH SHOULD BE USED FOR DISTRIBUTION      ]
 ] WITHIN THE CS.  WHEN ACQUIRING A DEU FROM OUTSIDE THE CS, DESELECT  ]
 ] THE DEU FROM THE CURRENT COMMANDER AND VERIFY THAT THE BIG "X" AND  ]
 ] "POLL FAIL" APPEAR BEFORE ASSIGNING A NEW COMMANDER INSIDE THE CS.  ]
 ]                                                                     ]
 ] CAUTION SHOULD BE EXERCISED BEFORE PASS REASSIGNMENT OF BUSES VIA   ]
 ] OPS MODE RECALLS OR OPS TRANSITIONS, IF THE BUS(ES) BEING REASSIGNED]
 ] WAS (WERE) COMMANDED BY A GPC WHICH PREVIOUSLY FAILED TO SYNC FROM  ]
 ] THE CS OR RS.  THE PRIOR BUS COMMANDER SHOULD BE POWERED OFF OR     ]
 ] DOWNMODED TO HALT BEFORE BUS RE-ASSIGNMENT IS INITIATED.            ]
 ]                                                                     ]
 ]                                                                     ]
 ] IF MORE THAN ONE OF THE I/O ERROR SIGNATURES IDENTIFIED             ]
 ] ABOVE ARE SEEN IN CONJUNCTION WITH BCE/BTU SEGMENT BYPASSES         ]
 ] OR CRT ERRORS, THE POSSIBILITY OF DUAL COMMANDERS AS A CAUSE        ]
 ] SHOULD BE CONSIDERED BEFORE ACTIONS SUCH AS I/O RESET ARE TAKEN.    ]
 ]                                                                     ]
 ] IF THE CREW OR GROUND RECOGNIZE A DUAL COMMANDER CONFLICT, THE      ]
 ] DUAL BUS ASSIGNMENT SHOULD BE CORRECTED ASAP OR ONE OF THE DUAL     ]
 ] COMMANDING GPCS SHOULD BE POWERED OFF OR MODED TO HALT ASAP.        ]
 ] HOWEVER, ONE OR MORE GPCS MAY FTS BEFORE ANY CORRECTIVE ACTION      ]
 ] CAN BE TAKEN.                                                       ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 @
