 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] PAUL TICE          ]    PASS PROGRAM NOTE        ]      50278       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] IBM/282-7297       ]      RELEASE NOTE( )        ] REV B: 01/03/91  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] OI03 AND SUBS                 ]  CREW ( )  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW (X)  GNC ( )  VU ( )  SM/PL ( )] G1                              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: LDB, CYCLE-WRAP, GPC                             ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: SLDB                                           ]
 ]_____________________________________________________________________]
 ] TITLE:                                                              ]
 ] DGI LDB CYCLE OVERRUN AFTER LAUNCH SEQUENCE HOLD                    ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] WHEN A LAUNCH HOLD IS REQUESTED, THE RS LAUNCH SEQUENCE ISSUES      ]
 ] TWO SUCCESSIVE MEC MASTER RESETS FOR MEC1 AND MEC2. THESE FOUR      ]
 ] OUTPUT TRANSACTIONS ARE AT A HIGHER PRIORITY THAN SRB DATA          ]
 ] ACQUISITION AND DGI GSE POLLING. THERE IS THEN A HIGH               ]
 ] PROBABILITY OF GETTING GPC ERRORS OF GROUP 7, CODE 06 (SRB IOQE     ]
 ] BUSY), OR GROUP 2, CODE OD (DGI LDB CYCLE OVERRUNS), WITHIN 1       ]
 ] SECOND OF THE LAUNCH HOLD REQUEST.                                  ]
 ]                                                                     ]
 ] IF A DGI CYCLE OVERRUN OCCURS ON THE LDB I/O CYCLE AFTER THE GPC    ]
 ] INTERROGATE WITH DATA CYCLE, THE "HERE COMES GPC DATA" (CONTAINING  ]
 ] L.S. HOLD RESPONSE) WILL NOT OCCUR UNTIL 80 MS. AFTER THE INT. WITH ]
 ] DATA CYCLE.  SINCE THE LPS FEP DETECTS THIS AS A BREAK IN THE LDB   ]
 ] PROTOCOL, THE LPS FEP WILL IGNORE THE L.S. RESPONSE (UNSOLICITED    ]
 ] DATA) AND WILL NOT RESPOND TO THE GPC STATUS REQUEST WHICH OCCURS   ]
 ] 40 MS. LATER.  THE GPC WILL LOG AN INITIAL TIMEOUT ERROR ON THIS    ]
 ] LDB I/O TRANSACTION.  THE GPC WILL RESEND THE MESSAGE AFTER RE-     ]
 ] STARTING THE LDB PROTOCOL CYCLE.                                    ]
 ]_____________________________________________________________________]
 ]USER RESPONSE:                                                       ]
 ]                                                                     ]
 ]    BE AWARE OF THE POSSIBILITY OF THE ABOVE ERROR CONDITION IN      ]
 ] CONJUNCTION WITH A L.S. HOLD.                                       ]
 ]    NOTE:  THIS BREAK IN LDB PROTOCOL AND RELATED LPS AND GPC ERROR  ]
 ] PROCESSING CAN OCCUR WITH ANY DGI PROCESS OVERRUN OR LDB I/O CYCLE  ]
 ] OVERRUN.                                                            ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM: PATTI A. THORNTON    DATE 02/06/91]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:   W. R. PRUETT      DATE 02/07/91]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 02/12/91 ]
 ]PF MGR:ELIZABETH FOUNTAIN DATE 02/07/91]------------------- -------- ]
 ]       ------------------     ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
 @
 DR50776
