Assembly listing generated by yaYUL

Source Code

These source-code files are part of a reconstructed copy of Skylark 048, the Block II Command Module (CM) Apollo Guidance Computer (AGC) software for the Skylab-2, Skylab-3, Skylab-4, and Apollo-Soyuz Test Project missions.

They have been created via disassembly of binary dumps of the original core rope memory modules actually flown on Skylab-2, part numbers 2010802-541, 2010802-551, 2010802-561, 2010802-571, 2010802-581, and 2010802-591. Access to these modules was provided by the New Mexico Museum of Space History, who we are much indebted to.

The source code for the Apollo 15, 16, and 17 software, Artemis 072, was used as a starting point. Heavy use was made of TRW 4900.5-244, Programmed Guidance Equations for Skylark Command Module Earth Orbital Program, dated 14 February 1972. This document contains pseudocode of essentially all of Skylark, using original program labels which have been copied for this source reconstruction.

Since only binary dumps (rather than listings) of Skylark are available as source material, all comments and labels are approximate. They have been taken from the Programmed Guidance Equations or other AGC programs where possible, or, in some places, written from scratch to match what we believe would have been in the original listing.

048896,000002: 048897,000003: 048898,000004: 048899,000005: 048900,000006: 048901,000007: 048902,000008: 048903,000009: 048904,000010: 048905,000011: 048906,000012: 048907,000013: 048908,000014: 048909,000015: 048910,000016: 048911,000017: 4000 048912,000018: 4000 048913,000019: 048914,000020: 048915,000021: 048916,000022: 5133 < 048919,000025: 5135 048920,000026: 5136 048921,000027: 048922,000028: 5137 048923,000029: 5140 048924,000030: 5141 048925,000031: 5142 048926,000032: 5143 048927,000033: 5144 048928,000034: 5145 048929,000035: 5146 048930,000036: 048931,000037: 048932,000038: < 048949,000055: 5162 048950,000056: 5163 048951,000057: 5164 048952,000058: 048953,000059: 048954,000060: 049314,000420: 049315,000421: 01,3165 049316,000422: 01,3166 049317,000423: 01,3167 049318,000424: 01,3170 049319,000425: 01,3171 049320,000426: 01,3172 049321,000427: 049322,000428: 049323,000429: 01,3174 049324,000430: 01,3175 049325,000431: 01,3176 049326,000432: 049327,000433: 049328,000434: 049329,000435: 049330,000436: 01,3177 049331,000437: < 049339,000445: 01,3206 049340,000446: 01,3207 049341,000447: 01,3210 049342,000448: 049343,000449: 01,3211 049344,000450: 01,3212 049345,000451: 01,3213 049346,000452: 01,3214 049347,000453: ## Copyright: Public domain. ## Filename: EXECUTIVE.agc ## Purpose: A section of Skylark revision 048. ## It is part of the source code for the Apollo Guidance Computer (AGC) ## for Skylab-2, Skylab-3, Skylab-4, and ASTP. No original listings of ## this software are available; instead, this file was created via ## disassembly of dumps of the core rope modules actually flown on ## Skylab-2. Access to these modules was provided by the New Mexico ## Museum of Space History. ## Assembler: yaYUL ## Contact: Ron Burkey <info@sandroid.org>. ## Website: www.ibiblio.org/apollo/index.html ## Mod history: 2023-09-04 MAS Created from Artemis 072. SETLOC EXECF2 BANK # TO ENTER A JOB REQUEST REQUIRING NO VAC AREA: COUNT* $$/EXEC 0">048917,000023: 5133 34346 NOVAC30 CAF PRIO30 /a>048918,000024: 5134 00004 NOVAC INHINT 65226 AD FAKEPRET # LOC(MPAC +6) - LOC(QPRET) 54063 TS NEWPRIO # PRIORITY OF NEW JOB + NOVAC C(FIXLOC) 00006 EXTEND 50002 INDEX Q # Q WILL BE UNDISTURBED THROUGHOUT. 30001 DCA 0 # 2CADR OF JOB ENTERED. 52066 DXCH NEWLOC 34767 CAF EXECBANK 56004 XCH FBANK 54061 TS EXECTEM1 12626 TCF NOVAC2 # ENTER EXECUTIVE BANK. # TO ENTER A JOB REQUEST REQUIRING A VAC AREA - E.G., ALL (PARTIALLY) INTERPRETIVE JOBS. 230">048933,000039: 5147 34764 FINVAC20 CAF PRIO20 3">048934,000040: 5150 00004 FINDVAC INHINT 54063 TS NEWPRIO 00006 EXTEND 50002 INDEX Q 30001 DCA 0 E">048939,000045: 5155 52066 SPVACIN DXCH NEWLOC 34767 CAF EXECBANK 56004 XCH FBANK 12604 TCF FINDVAC2 # OFF TO EXECUTIVE SWITCHED-BANK. # TO ENTER A FINDVAC WITH THE PRIORITY IN NEWPRIO TO THE 2CADR ARRIVING IN A AND L: # USERS OF SPVAC MUST INHINT BEFORE STORING IN NEWPRIO. /a>048948,000054: 5161 56002 SPVAC XCH Q 67701 AD NEG2 56002 XCH Q 15155 TCF SPVACIN # TO SUSPEND A BASIC JOB SO A HIGHER PRIORITY JOB MAY BE SERVICED: >048955,000061: 5165 22002 CHANG1 LXCH Q 34767 CAF EXECBANK 56006 XCH BBANK 12705 TCF CHANJOB # TO SUSPEND AN INTERPRETIVE JOB: >048962,000068: 5171 40164 CHANG2 CS LOC # NEGATIVE LOC SHOWS JOB = INTERPRETIVE. # ITRACE (4) REFERS TO "CHANG2". 54001 TS L 34767 +2 CAF EXECBANK 54006 TS BBANK 12704 TCF CHANJOB -1 # TO VOLUNTARILY SUSPEND A JOB UNTIL THE COMPLETION OF SOME ANTICIPATED EVENT (I/O EVENT ETC.): 550">048971,000077: 5176 54164 JOBSLEEP TS LOC 34767 CAF EXECBANK 54004 TS FBANK 12775 TCF JOBSLP1 # TO AWAKEN A JOB PUT TO SLEEP IN THE ABOVE FASHION: 5">048978,000084: 5202 00004 JOBWAKE INHINT 54065 TS NEWLOC 45000 CS TWO # EXIT IS VIA FINDVAC/NOVAC PROCEDURES. 26002 ADS Q 34767 CAF EXECBANK 56004 XCH FBANK 13022 TCF JOBWAKE2 # TO CHANGE THE PRIORITY OF A JOB CURRENTLY UNDER EXECUTION: E47">048988,000094: 5211 00004 PRIOCHNG INHINT # NEW PRIORITY ARRIVES IN A. RETURNS TO 54063 TS NEWPRIO # CALLER AS SOON AS NEW JOB PRIORITY IS 34767 CAF EXECBANK # HIGHEST. PREPARE FOR POSSIBLE BASIC- 56006 XCH BBANK # STYLE CHANGE-JOB. 54165 TS BANKSET 30002 CA Q 13071 TCF PRIOCH2 # TO REMOVE A JOB FROM EXECUTIVE CONSIDERATIONS: F42">048998,000104: 5220 34767 ENDOFJOB CAF EXECBANK 54004 TS FBANK 13102 TCF ENDJOB1 4">049002,000108: 5223 30061 ENDFIND CA EXECTEM1 # RETURN TO CALLER AFTER JOB ENTRY 54004 TS FBANK # COMPLETE. 16710 TCF Q+2 E4B">049005,000111: 5226 4767 EXECBANK EQUALS BIT11 # THIS IS TRUE IF FINDVAC2 STAYS IN BANK 01 554">049007,000113: 5226 00110 FAKEPRET ADRES MPAC -36D # LOC(MPAC +6) - LOC(QPRET) # LOCATE AN AVAILABLE VAC AREA. SETLOC EXECB1 BANK COUNT* $$/EXEC # ******** IF THE EXECUTIVE IS # MOVED OUT OF BANK 01 # DONT FORGET TO CHANGE # THE VALUE OF # ****** EXECBANK **** 332">049020,000126: 01,2604 54061 FINDVAC2 TS EXECTEM1 # (SAVE CALLER'S BANK FIRST.) 10400 CCS VAC1USE 12621 TCF VACFOUND 10454 CCS VAC2USE 12621 TCF VACFOUND 10530 CCS VAC3USE 12621 TCF VACFOUND 10604 CCS VAC4USE 12621 TCF VACFOUND 10660 CCS VAC5USE 12621 TCF VACFOUND 07750 TC BAILOUT 31201 OCT 31201 # NO VAC AREAS E44">049034,000140: 01,2621 65000 VACFOUND AD TWO # RESERVE THIS VAC AREA BY STORING A ZERO 22007 ZL # IN ITS VAC USE REGISTER AND STORE THE 50000 INDEX A # ADDRESS OF THE FIRST WORD OF IT IN THE 21777 LXCH 0 -1 # LOW NINE BITS OF THE PRIORITY WORD. 26063 ADS NEWPRIO >049040,000146: 01,2626 35003 NOVAC2 CAF ZERO # NOVAC ENTERS HERE. FIND A CORE SET. 54064 TS LOCCTR 32635 CAF NO.CORES # SEVEN SETS OF ELEVEN REGISTERS EACH. >049043,000149: 01,2631 54062 NOVAC3 TS EXECTEM2 50064 INDEX LOCCTR 10167 CCS PRIORITY # EACH PRIORITY REGISTER CONTAINS -0 IF 12675 TCF NEXTCORE # THE CORRESPONDING CORE SET IS AVAILABLE. 553">049047,000153: 01,2635 00006 NO.CORES DEC 6 B-14 12675 TCF NEXTCORE # AN ACTIVE JOB HAS A POSITIVE PRIORITY # BUT A DORMANT JOB'S PRIORITY IS NEGATIVE E44">049051,000157: 01,2637 30063 CORFOUND CA NEWPRIO # SET THE PRIORITY OF THIS JOB IN THE CORE 50064 INDEX LOCCTR # SET'S PRIORITY REGISTER AND SET THE 54167 TS PRIORITY # JOB'S PUSH-DOWN POINTER AT THE BEGINNING 75034 MASK LOW9 # OF THE WORK AREA AND OVERFLOW INDICATOR 50064 INDEX LOCCTR 54166 TS PUSHLOC # OFF TO PREPARE FOR INTERPRETIVE PROGRAMS 10064 CCS LOCCTR # IF CORE SET ZERO IS BEING LOADED, SET UP 12662 TCF SETLOC # OVFIND AND FIXLOC IMMEDIATELY. 54121 TS OVFIND 30166 CA PUSHLOC 54120 TS FIXLOC 354">049064,000170: 01,2652 10067 SPECTEST CCS NEWJOB # SEE IF ANY ACTIVE JOBS WAITING (RARE). 12662 TCF SETLOC # MUST BE AWAKENED BUT UNCHANGED JOB. 12655 NOOP # CANNOT GET HERE 12656 NOOP # CANNOT GET HERE 54067 TS NEWJOB # +0 SHOWS ACTIVE JOB ALREADY SET. 52066 DXCH NEWLOC 52165 DXCH LOC 15223 TCF ENDFIND >049073,000179: 01,2662 52066 SETLOC DXCH NEWLOC # SET UP THE LOCATION REGISTERS FOR THIS 50064 INDEX LOCCTR 52165 DXCH LOC 50067 INDEX NEWJOB # THIS INDEX INSTRUCTION INSURES THAT THE 40167 CS PRIORITY # HIGHEST ACTIVE PRIORITY WILL BE COMPARED 60063 AD NEWPRIO # WITH THE NEW PRIORITY TO SEE IF NEWJOB 00006 EXTEND # SHOULD BE SET TO SIGNAL A SWITCH. 65223 BZMF ENDFIND 30064 CA LOCCTR # LOCCTR IS LEFT SET AT THIS CORE SET IF 54067 TS NEWJOB # THE CALLER WANTS TO LOAD ANY MPAC 15223 TCF ENDFIND # REGISTERS, ETC. 245">049085,000191: 01,2675 33032 NEXTCORE CAF COREINC 26064 ADS LOCCTR 10062 CCS EXECTEM2 12631 TCF NOVAC3 07750 TC BAILOUT # NO CORE SETS. 31202 OCT 31202 # THE FOLLOWING ROUTINE SWAPS CORE SET 0 WITH THAT WHOSE RELATIVE ADDRESS IS IN NEWJOB. 22164 -2 LXCH LOC 30165 -1 CAE BANKSET # BANKSET, NOT BBANK, HAS RIGHT CONTENTS. 2">049096,000202: 01,2705 00004 CHANJOB INHINT 00006 EXTEND 04007 ROR SUPERBNK # PICK UP CURRENT SBANK FOR BBCON 56001 XCH L # LOC IN A AND BBCON IN L. 50067 +4 INDEX NEWJOB # SWAP LOC AND BANKSET. 52165 DXCH LOC 52165 DXCH LOC 30165 CAE BANKSET 00006 EXTEND 01007 WRITE SUPERBNK # SET SBANK FOR NEW JOB. 52155 DXCH MPAC # SWAP MULTI-PURPOSE ACCUMULATOR AREAS. 50067 INDEX NEWJOB 52155 DXCH MPAC 52155 DXCH MPAC 52157 DXCH MPAC +2 50067 INDEX NEWJOB 52157 DXCH MPAC +2 52157 DXCH MPAC +2 52161 DXCH MPAC +4 50067 INDEX NEWJOB 52161 DXCH MPAC +4 52161 DXCH MPAC +4 52163 DXCH MPAC +6 50067 INDEX NEWJOB 52163 DXCH MPAC +6 52163 DXCH MPAC +6 35003 CAF ZERO 56121 XCH OVFIND # MAKE PUSHLOC NEGATIVE IF OVFIND NZ. 00006 EXTEND 12745 BZF +3 40166 CS PUSHLOC 54166 TS PUSHLOC 52167 DXCH PUSHLOC 50067 INDEX NEWJOB 52167 DXCH PUSHLOC 52167 DXCH PUSHLOC # SWAPS PUSHLOC AND PRIORITY. 35034 CAF LOW9 # SET FIXLOC TO BASE OF VAC AREA. 70167 MASK PRIORITY 54120 TS FIXLOC 10166 CCS PUSHLOC # SET OVERFLOW INDICATOR ACCORDING TO 35003 CAF ZERO 12763 TCF ENDPRCHG -1 40166 CS PUSHLOC 54166 TS PUSHLOC 35001 CAF ONE 56121 XCH OVFIND 54067 -1 TS NEWJOB 847">049147,000253: 01,2764 00003 ENDPRCHG RELINT 52165 DXCH LOC # BASIC JOBS HAVE POSITIVE ADDRESSES, SO 00006 EXTEND # DISPATCH WITH A DTCB. 62771 BZMF +2 # IF INTERPRETIVE, SET UP EBANK, ETC. 52006 DTCB 40000 COM # EPILOGUE TO JOB CHANGE FOR INTERPRETIVE 65001 AD ONE 54164 TS LOC # RESUME. 16017 TCF INTRSM # COMPLETE JOBSLEEP PREPARATIONS. 1">049161,000267: 01,2775 00004 JOBSLP1 INHINT 40167 CS PRIORITY # NNZ PRIORITY SHOWS JOB ASLEEP. 54167 TS PRIORITY 36043 CAF LOW7 70006 MASK BBANK 00006 EXTEND 04007 ROR SUPERBNK # SAVE OLD SUPERBANK VALUE. 54165 TS BANKSET 45003 CS ZERO 2">049170,000276: 01,3006 54131 JOBSLP2 TS BUF +1 # HOLDS - HIGHEST PRIORITY. 13117 TCF EJSCAN # SCAN FOR HIGHEST PRIORITY ALA ENDOFJOB. 732">049173,000279: 01,3010 00004 NUCHANG2 INHINT # QUICK... DONT LET NEWJOB CHANGE TO +0. 10067 CCS NEWJOB 13015 TCF +3 # NEWJOB STILL PNZ 00003 RELINT # NEW JOB HAS CHANGED TO +0. WAKE UP JOB 13207 TCF ADVAN +2 # VIA NUDIRECT. (VERY RARE CASE.) 35000 CAF TWO 00006 EXTEND 05011 WOR DSALMOUT # TURN ON ACTIVITY LIGHT 52165 DXCH LOC # AND SAVE ADDRESS INFO FOR BENEFIT OF 12711 TCF CHANJOB +4 # POSSIBLE SLEEPING JOB. # TO WAKE UP A JOB, EACH CORE SET IS FOUND TO LOCATE ALL JOBS WHICH ARE ASLEEP. IF THE FCADR IN THE # LOC REGISTER OF ANY SUCH JOB MATCHES THAT SUPPLIED BY THE CALLER, THAT JOB IS AWAKENED. IF NO JOB IS FOUND, # LOCCTR IS SET TO -1 AND NO FURTHER ACTION TAKES PLACE. 532">049189,000295: 01,3022 54061 JOBWAKE2 TS EXECTEM1 35003 CAF ZERO # BEGIN CORE SET SCAN. 54064 TS LOCCTR 32635 CAF NO.CORES 534">049193,000299: 01,3026 54062 JOBWAKE4 TS EXECTEM2 50064 INDEX LOCCTR 10167 CCS PRIORITY 13034 TCF JOBWAKE3 # ACTIVE JOB - CHECK NEXT CORE SET. 3">049197,000303: 01,3032 00014 COREINC DEC 12 B-14 # 12 REGISTERS PER CORE SET. 13043 TCF WAKETEST # SLEEPING JOB - SEE IF CADR MATCHES. 533">049200,000306: 01,3034 33032 JOBWAKE3 CAF COREINC 26064 ADS LOCCTR 10062 CCS EXECTEM2 13026 TCF JOBWAKE4 45001 CS ONE # EXIT IF SLEEPING JOB NOT FOUND. 54064 TS LOCCTR 15223 TCF ENDFIND 354">049208,000314: 01,3043 40065 WAKETEST CS NEWLOC 50064 INDEX LOCCTR 60164 AD LOC 00006 EXTEND 13051 BZF +2 # IF MATCH. 13034 TCF JOBWAKE3 # EXAMINE NEXT CORE SET IF NO MATCH. 50064 INDEX LOCCTR # RE-COMPLEMENT PRIORITY TO SHOW JOB AWAKE 40167 CS PRIORITY 54063 TS NEWPRIO 50064 INDEX LOCCTR 54167 TS PRIORITY 44344 CS FBANKMSK # MAKE UP THE 2CADR OF THE WAKE ADDRESS 70065 MASK NEWLOC # USING THE CADR IN NEWLOC AND THE EBANK 64767 AD 2K # HALF OF BBANK SAVED IN BANKSET. 56065 XCH NEWLOC 74344 MASK FBANKMSK 50064 INDEX LOCCTR 60165 AD BANKSET 54066 TS NEWLOC +1 10064 CCS LOCCTR # SPECIAL TREATMENT IF THIS JOB WAS 12662 TCF SETLOC # ALREADY IN THE RUN (0) POSITION. 12652 TCF SPECTEST # PRIORITY CHANGE. CHANGE THE CONTENTS OF PRIORITY AND SCAN FOR THE JOB OF HIGHEST PRIORITY. 2">049236,000342: 01,3071 54164 PRIOCH2 TS LOC 35003 CAF ZERO # SET FLAG TO TELL ENDJOB SCANNER IF THIS 54130 TS BUF # JOB IS STILL HIGHEST PRIORITY. 35034 CAF LOW9 70167 MASK PRIORITY 60063 AD NEWPRIO 54167 TS PRIORITY 40000 COM 13006 TCF JOBSLP2 # AND TO EJSCAN. # RELEASE THIS CORE SET AND VAC AREA AND SCAN FOR THE JOB OF HIGHEST ACTIVE PRIORITY. 1">049248,000354: 01,3102 00004 ENDJOB1 INHINT 45003 CS ZERO 54131 TS BUF +1 56167 XCH PRIORITY 75034 MASK LOW9 54001 TS L 45226 CS FAKEPRET 60001 AD L 00006 EXTEND 63117 BZMF EJSCAN # NOVAC ENDOFJOB 10001 CCS L 50000 INDEX A 54000 TS 0 >049265,000371: 01,3117 10203 EJSCAN CCS PRIORITY +12D 03164 TC EJ1 1361 EBANK= SELFRET E4B">049268,000374: 01,3121 66102 SELFBANK BBCON SELFCHK # CANNOT GET HERE 13123 TCF +1 10217 CCS PRIORITY +24D # EXAMINE EACH PRIORITY REGISTER TO FIND 03164 TC EJ1 # THE JOB OF HIGHEST ACTIVE PRIORITY. 031">049273,000379: 01,3125 40201 OCT40201 OCT 40201 # CANNOT GET HERE 13127 TCF +1 10233 CCS PRIORITY +36D 03164 TC EJ1 >049278,000384: 01,3131 67610 -CCSPR -CCS PRIORITY 13133 TCF +1 10247 CCS PRIORITY +48D 03164 TC EJ1 452">049283,000389: 01,3135 03732 PHS2CADR GENADR PHSPART2 # CANNOT GET HERE 13137 TCF +1 10263 CCS PRIORITY +60D 03164 TC EJ1 452">049288,000394: 01,3141 03510 PRT2CADR GENADR GETPART2 # CANNOT GET HERE 13143 TCF +1 10277 CCS PRIORITY +72D 03164 TC EJ1 452">049293,000399: 01,3145 05345 LGCLCADR GENADR LONGCALL # CANNOT GET HERE 13147 TCF +1 # EVALUATE THE RESULTS OF THE SCAN. 10131 CCS BUF +1 # SEE IF THERE ARE ANY ACTIVE JOBS WAITING 2">049300,000406: 01,3150 53271 GETCADR DXCH LONGCADR # CANNOT GET HERE 05227 TC SUPDXCHZ 13154 TCF +2 13177 TCF DUMMYJOB 10130 CCS BUF # BUF IS ZERO IF THIS IS A PRIOCHNG AND 13157 TCF +2 # CHANGED PRIORITY IS STILL HIGHEST. 12763 TCF ENDPRCHG -1 50000 INDEX A # OTHERWISE, SET NEWJOB TO THE RELATIVE 27777 CAF 0 -1 # ADDRESS OF THE NEW JOB'S CORE SET. 63131 AD -CCSPR 54067 TS NEWJOB 12703 TCF CHANJOB -2 01,3164 54132 EJ1 TS BUF +2 60131 AD BUF +1 # - OLD HIGH PRIORITY. 10000 CCS A 40132 CS BUF +2 13173 TCF EJ2 # NEW HIGH PRIORITY. 13172 NOOP 16710 TCF Q+2 01,3173 54131 EJ2 TS BUF +1 30002 CA Q 54130 TS BUF # FOR LOCATING CCS PRIORITY + X INSTR. 16710 TCF Q+2 # IDLING AND COMPUTER ACTIVITY (GREEN) LIGHT MAINTENANCE. THE IDLING ROUTINE IS NOT A JOB IN ITSELF, # BUT RATHER A SUBROUTINE OF THE EXECUTIVE. 1361 EBANK= SELFRET # SELF-CHECK STORAGE IN EBANK. F42">049332,000438: 01,3177 45003 DUMMYJOB CS ZERO # SET NEWJOB TO -0 FOR IDLING. 54067 TS NEWJOB 00003 +2 RELINT 45000 CS TWO # TURN OFF THE ACTIVITY LIGHT. 00006 EXTEND 03011 WAND DSALMOUT /a>049338,000444: 01,3205 10067 ADVAN CCS NEWJOB # IS A NEWJOB ACTIVE ? 13010 TCF NUCHANG2 # YES... ONE REQUIRING A CHANGE JOB. 35000 +2 CAF TWO # NEW JOB ALREADY IN POSITION FOR 13215 TCF NUDIRECT # EXECUTION. 31361 CA SELFRET 54001 TS L # PUT RETURN ADDRESS IN L. 33121 CAF SELFBANK 15230 TCF SUPDXCHZ +1 # AND DISPATCH JOB. 354">049348,000454: 01,3215 00006 NUDIRECT EXTEND # TURN THE GREEN LIGHT BACK ON. 05011 WOR DSALMOUT 52165 DXCH LOC # JOBS STARTED IN THIS FASHION MUST BE 15227 TCF SUPDXCHZ SETLOC EXECF2 BANK COUNT* $$/EXEC # SUPDXCHZ - ROUTINE TO TRANSFER TO SUPERBANK. # CALLING SEQUENCE # TCF SUPDXCHZ WITH 2CADR OF DESIRED LOCATION IN A + L. 85A">049362,000468: 5227 56001 SUPDXCHZ XCH L # BASIC. 00006 +1 EXTEND 01007 WRITE SUPERBNK 54006 TS BBANK 00001 TC L >049368,000474: 5234 77677 NEG100 OCT 77677 Parent file is MAIN.agc