Source Code
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These source-code files are part of a reconstructed copy of LM131 revision 1,
the final release of the Apollo 13 Lunar Module (LM) Apollo Guidance Computer
(AGC) software.
The source reconstruction began with source code of Luminary 131 previously
transcribed from a digitized copy of that program. A dump of the flight spare
core rope memory module B5, part number 2010802-171, serial number RAY 411,
was obtained. This module is the only module different between Luminary 131
and LM131 revision 1. The dump was disassembled and all changes were incorporated
into these source files. Note that page numbers in the reconstructed code match
those on the Luminary 131 printout, although the changed code would likely have
changed page numbers for a real LM131 revision 1 listing.
Comments from the original source code are prefixed with a single '#' symbol,
whereas comments added later are prefixed by "##" or "###". Report any errors
noted by creating an
issue report at the Virtual AGC
project's GitHub repository.
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013889,000002: ## Copyright: Public domain.
013890,000003: ## Filename: R63.agc
013891,000004: ## Purpose: A section of LM131 revision 1.
013892,000005: ## It is part of the reconstructed source code for the final
013893,000006: ## release of the flight software for the Lunar Module's (LM)
013894,000007: ## Apollo Guidance Computer (AGC) for Apollo 13. The code has
013895,000008: ## been reconstructed from a listing of Luminary 131 and a dump
013896,000009: ## of a core rope memory module B5, part number 2010802-171,
013897,000010: ## which is the only module different between LM131 revision 1
013898,000011: ## and Luminary 131. The executable generated from this source
013899,000012: ## has been verified against the module dump, so while the names,
013900,000013: ## comments, and ordering may not be exactly correct, the
013901,000014: ## resulting binary is.
013902,000015: ## Reference: pp. 340-343
013903,000016: ## Assembler: yaYUL
013904,000017: ## Contact: Ron Burkey <info@sandroid.org>.
013905,000018: ## Website: www.ibiblio.org/apollo/index.html
013906,000019: ## Mod history: 2022-10-28 MAS Created from Luminary 131.
013907,000020:
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Page 340
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013909,000022: # SUBROUTINE NAME: V89CALL
013910,000023: # MOD NO: 0 DATE: 9 JAN 1968
013911,000024: # MOD BY: DIGITAL DEVEL GROUP LOG SECTION: R63
013912,000025:
013913,000026: # FUNCTIONAL DESCRIPTION:
013914,000027:
013915,000028: # CALLED BY VERB 89 ENTER DURING P00. PRIO 10 USED. CALCULATES AND
013916,000029: # DISPLAYS FINAL FDAI BALL ANGLES TO POINT LM +X OR +Z AXIS AT CSM.
013917,000030:
013918,000031: # 1. KEY IN V 89 E ONLY IF IN PROG 00. IF NOT IN P00, OPERATOR ERROR AND
013919,000032: # EXIT R63, OTHERWISE CONTINUE.
013920,000033:
013921,000034: # 2. IF IN P00, DO IMU STATUS CHECK ROUTINE (R02BOTH). IF IMU ON AND ITS
013922,000035: # ORIENTATION KNOWN TO LGC, CONTINUE.
013923,000036:
013924,000037: # 3. FLASH DISPLAY V 04 N 06. R2 INDICATES WHICH SPACECRAFT AXIS IS TO
013925,000038: # BE POINTED AT CSM. INITIAL CHOICE IS PREFERRED (+Z) AXIS (R2=1).
013926,000039: # ASTRONAUT CAN CHANGE TO (+X) AXIS (R2 NOT =1) BY V 22 E 2 E. CONTINUE
013927,000040: # AFTER KEYING IN PROCEED.
013928,000041:
013929,000042: # 4. BOTH VEHICLE STATE VECTORS UPDATED BY CONIC EQS.
013930,000043:
013931,000044: # 5. HALF MAGNITUDE UNIT LOS VECTOR (IN STABLE MEMBER COORDINATES) AND
013932,000045: # HALF MAGNITUDE UNIT SPACECRAFT AXIS VECTOR (IN BODY COORDINATES)
013933,000046: # PREPARED FOR VECPOINT.
013934,000047:
013935,000048: # 6. GIMBAL ANGLES FROM VECPOINT TRANSFORMED INTO FDAI BALL ANGLES BY
013936,000049: # BALLANGS. FLASH DISPLAY V 06 N 18 AND AWAIT RESPONSE.
013937,000050:
013938,000051: # 7. RECYCLE - RETURN TO STEP 4.
013939,000052: # TERMINATE - EXIT R63.
013940,000053: # PROCEED - RESET 3AXISFLG AND CALL R60LEM FOR ATTITUDE MANEUVER.
013941,000054:
013942,000055: # CALLING SEQUENCE: V 89 E.
013943,000056:
013944,000057: # SUBROUTINES CALLED: CHKPOOH, R02BOTH, GOXDSPF, CSMCONIC, LEMCONIC,
013945,000058: # VECPOINT, BALLANGS, R60LEM.
013946,000059:
013947,000060: # NORMAL EXIT MODES: TC ENDEXT
013948,000061:
013949,000062: # ALARMS: 1. OPERATOR ERROR IF NOT IN P00.
013950,000063: # 2. PROGRAM ALARM IF IMU IS OFF.
013951,000064: # 3. PROGRAM ALARM IF IMU ORIENTATION IS UNKNOWN.
013952,000065:
013953,000066: # OUTPUT: NONE
013954,000067:
013955,000068: # ERASABLE INITIALIZATION REQUIRED: NONE
013956,000069:
013957,000070: # DEBRIS: OPTION1, +1, TDEC1, POINTVSM, SCAXIS, CPHI, CTHETA, CPSI,
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Page 341
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013959,000072: # 3AXISFLG.
013960,000073:
013961,000074: 06,3723 E4,1606 EBANK= RONE
013962,000075: 32,2217 BANK 32
013963,000076: 26,2000 SETLOC BAWLANGS
013964,000077: 26,2000 BANK
013965,000078:
013966,000079: 26,2022 COUNT* $$/R63
013967,000080: 26,2022 04616 V89CALL TC BANKCALL # IMU STATUS CHECK. RETURNS IF ORIENTATION
013968,000081: 26,2023 11233 CADR R02BOTH # KNOWN. ALARMS IF NOT.
013969,000082: 26,2024 36250 CAF THREE # ALLOW ASTRONAUT TO SELECT DESIRED
013970,000083: 26,2025 55050 TS OPTIONX # TRACKING ATTITUDE AXIS.
013971,000084: 26,2026 34753 CAF ONE
013972,000085: 26,2027 55051 TS OPTIONX +1
013973,000086: 26,2030 32117 CAF VB04N12 # V 04 N 12
013974,000087: 26,2031 04616 TC BANKCALL
013975,000088: 26,2032 20477 CADR GOFLASH
013976,000089: 26,2033 05472 TC ENDEXT # TERMINATE
013977,000090: 26,2034 02036 TC +2 # PROCEED
013978,000091: 26,2035 02030 TC -5 # DATA IN. OPTION1+1 = 1 FOR Z AXIS
013979,000092: 26,2036 06042 V89RECL TC INTPRET # = 2 FOR X AXIS
013980,000093: 26,2037 43234 RTB DAD
013981,000094: 26,2040 21574 LOADTIME # READ PRESENT TIME
013982,000095: 26,2041 14122 DP1MIN
013983,000096: 26,2042 02205 STORE TSTART82 # SAVE TIME FOR LEMCONIC CALL
013984,000097: 26,2043 34041 STCALL TDEC1 # STORE TIME FOR CSMCONIC CALL
013985,000098: 26,2044 27065 CSMCONIC # CSM STATE VECTOR UPDATE
013986,000099: 26,2045 77775 VLOAD # CSMCONIC LEFT R VECTOR IN RATT
013987,000100: 26,2046 00001 RATT
013988,000101: 26,2047 16207 STODL RONE # SAVE FOR LINE OF SIGHT (LOS) COMPUTATION
013989,000102: 26,2050 02205 TSTART82
013990,000103: 26,2051 34041 STCALL TDEC1 # STORE TIME FOR LEMCONIC CALL
013991,000104: 26,2052 27077 LEMCONIC # LEM STATE VECTOR UPDATE
013992,000105: 26,2053 52375 VLOAD VSU # CSM POSITION - LEM POSITION = LOS
013993,000106: 26,2054 02207 RONE # LOS VECTOR LEFT IN MPAC
013994,000107: 26,2055 00001 RATT
013995,000108: 26,2056 47121 MXV RTB # (REFSMMAT X LOS). TRANSFORMS LOS FROM
013996,000109: 26,2057 01734 REFSMMAT # REFERENCE COORD TO STAB MEMB COORD.
013997,000110: 26,2060 21727 NORMUNIT
013998,000111: 26,2061 03773 STORE POINTVSM # STORE LOS FOR VECPOINT CALL
013999,000112: 26,2062 77776 EXIT
014000,000113: 26,2063 41051 CS OPTIONX +1 # 1 FOR Z AXIS. 2 FOR X AXIS.
014001,000114: 26,2064 64753 AD ONE
014002,000115: 26,2065 00006 EXTEND
014003,000116: 26,2066 12113 BZF ALINEZ
014004,000117: 26,2067 06042 ALINEX TC INTPRET # X AXIS ALIGNMENT
014005,000118: 26,2070 77775 VLOAD
014006,000119: 26,2071 06522 UNITX # READ (.5, 0, 0)
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014008,000121: 26,2072 37765 V89CALL1 STCALL SCAXIS # STORE SELECTED ALIGNMENT AXIS
014009,000122: 26,2073 56040 VECPOINT # PUTS DESIRED GIM ANG (OG,IG,MG) IN TMPAC
014010,000123: 26,2074 00322 STORE CPHI # STORE GIMBAL ANGLES FOR BALLANGS CALL.
014011,000124: 26,2075 77776 EXIT
014012,000125: 26,2076 04616 TC BANKCALL
014013,000126: 26,2077 54272 CADR BALLANGS # PUTS DESIRED BALL ANGLES IN FDAIX,Y,Z
014014,000127: 26,2100 32120 CAF VB06N18 # V 06 N 18
014015,000128: 26,2101 04616 TC BANKCALL # NOUN 18 REFERS TO FDAIX,Y,Z
014016,000129: 26,2102 20477 CADR GOFLASH
014017,000130: 26,2103 05472 TC ENDEXT # TERMINATE
014018,000131: 26,2104 02106 TC +2 # PROCEED
014019,000132: 26,2105 02036 TC V89RECL # RECYCLE
014020,000133: 26,2106 05516 TC DOWNFLAG # RESET 3 AXIS FLAG
014021,000134: 26,2107 00124 ADRES 3AXISFLG # RESET BIT6 FLAG WORD 5
014022,000135: 26,2110 04616 TC BANKCALL # PERFORMS LEM MANEUVER TO ALIGN SELECTED
014023,000136: 26,2111 54123 CADR R60LEM # SPACECRAFT AXIS TO CSM.
014024,000137: 26,2112 15472 TCF ENDEXT # TERMINATE R63
014025,000138:
014026,000139: 26,2113 06042 ALINEZ TC INTPRET # Z AXIS ALIGNMENT
014027,000140: 26,2114 52175 VLOAD GOTO
014028,000141: 26,2115 06516 UNITZ # READ (0, 0, .5)
014029,000142: 26,2116 54072 V89CALL1
014030,000143:
014031,000144: 26,2117 01014 VB04N12 VN 412
014032,000145: 26,2120 01422 VB06N18 VN 0618
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Page 343
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014034,000147: 26,2121 00000 13560 DP1MIN 2DEC 6000 B-28
014035,000148:
End of include-file R63.agc. Parent file is MAIN.agc