 +_____________________________________________________________________
  AUTHOR:                                          DR:              
  S. EHMRY               PASS PROGRAM NOTE               107469     
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE:            
  LSIS/282-7267            RELEASE NOTE( )               01/25/95   
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  OI/FLIGHT EFFECTIVITY:          USER AFFECTED:                     
    OI-24                         CREW (X)  GROUND (X)  DUMP ONLY ( )
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         MAJOR SOFTWARE AREA:        OPS MODES AFFECTED:             
 SSW ( )  GNC ( )  VU ( )  SM/PL (X)   S2, S4                        
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  SOFTWARE SUB-AREA:  PCS, SM                                         
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  PRINCIPAL FUNCTIONS:  S4.12, S7.1.1                                 
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  TITLE:                                                              
             PCS/SL I/O TERMINATION AT OPS TRANSITION                 
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  DESCRIPTION:                                                        
                                                                      
  OPS TRANSITION PROCESSING ERRONEOUSLY CHANGES THE TIMING OF THE SL  
  READ/WRITE PROTOCOL POSSIBLY RESULTING IN SL LINK ERROR ANNUNCIA-   
  TIONS (212 SL LINK TERM & 212 SL LINK ERR) WHICH DO NOT ALLOW       
  FURTHER COMMUNICATION BETWEEN PCS AND SL.  IF A PCS SEQUENCE IS     
  ACTIVE WHEN AN SM OPS TRANSITION IS REQUESTED AND THERE ARE SPACELAB
  COMMANDS IN THE PCS SEQUENCE'S SAFING STEPS, THESE SPACELAB COMMANDS
  (IN THE SAFING STEPS) WILL NOT BE SUCCESSFULLY EXECUTED.            
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________
 USER RESPONSE:  TO AVOID THIS PROBLEM, TERMINATE ALL PCS SEQUENCES   
  THROUGH ITEM 12 ON SPEC 90.  MONITOR THE SEQUENCE NAMES IN THE UPPER
  RIGHT CORNER OF THE SPEC, AS SEQUENCES THAT HAVE BEEN DEACTIVATED   
  WILL NO LONGER BE LISTED IN THIS AREA.  THEN, AFTER ALL THE PCS     
  SEQUENCES HAVE TERMINATED, DISABLE THE SPACELAB CHANNELS THROUGH    
  ITEMS 3 AND/OR 6 ON SPEC 212 BEFORE REQUESTING AN OPS TRANSITION.   
                                                                      
  IF THIS PROBLEM DOES OCCUR, BE AWARE THAT COMMANDS WHICH WERE       
  INTENDED FOR SPACELAB IN THE PCS SAFING STEPS WERE NOT SENT.        
                                                                      
  NOTE:  THIS PROBLEM DOES NOT AFFECT SUBSEQUENT INITIATION OF        
         SPACELAB POLLING IN THE SM OPS.                              
 _____________________________________________________________________
 CONCURRENCE:                           APPROVAL:                    
 LSIS:  HUGH D. STOVALL    DATE 03/15/95                             
      -------------------      ---------                             
 ASD:   ERIC C. BINGHAM    DATE 03/16/95                             
      -------------------      --------- DARRELL E. STAMPER 03/22/95 
 PF MGR:  J. D. BAGWELL    DATE 03/16/95------------------- -------- 
        -----------------      --------- CHAIRMAN, SASCB      DATE   
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