Source Code
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These source-code files are part of a reconstructed copy of Comanche 51, the
initial release (though not the final mission release) of the Apollo 11
Command Module (CM) Apollo Guidance Computer (AGC) software. The flown, final
release was Comanche 55. The reconstruction is believed to be exactly accurate,
but in the absence of an actual Apollo-era listing of Comanche 51, some
explanation of the reconstruction process is needed to insure confidence in
that accuracy.
The starting point was the source code of Comanche 55, whose original source code
is available. Comanche 55 source code was then modified by undoing changes known
to have been made between revisions 51 and 55. The most-significant steps involved
reverting changes related to the R-2 lunar potential model, the details of which
were known from the previous, separate, independent reconstruction of the Apollo 10
Lunar Module software Luminary 69/2. The now-reconstructed
Comanche 51 source code was verified by assembling it and checking that the assembled
code had the expected known-correct memory-bank checksums. Note that page numbers in
the reconstructed code match those on the Comanche 55 or Luminary 69 printouts, although
the source code would likely have different page numbers in a contemporary Comanche 51 listing.
Annotations that were not present in the contemporary source code have been added to
the reconstructed code to justify each change relative to Comanche 55. Here's a guide
to some of the Apollo documentation relevant to those annotations:
Among documentation not actually referenced in the annotations, there is
a short writeup about the reconstruction process in our software repository
that may be helpful in understanding it from a different perspective. There's also
a handy table
that lists what the number of memory-words should be for each routine in Comanche 51,
which could make a nice double-check; however, we've not performed that double-check ourselves.
Comments expected to have been present in 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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021486,000002: ## Copyright: Public domain.
021487,000003: ## Filename: R31.agc
021488,000004: ## Purpose: A section of Comanche revision 051.
021489,000005: ## It is part of the reconstructed source code for the
021490,000006: ## original release of the flight software for the Command
021491,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
021492,000008: ## The code has been recreated from a copy of Comanche 055. It
021493,000009: ## has been adapted such that the resulting bugger words
021494,000010: ## exactly match those specified for Comanche 51 in NASA drawing
021495,000011: ## 2021153D, which gives relatively high confidence that the
021496,000012: ## reconstruction is correct.
021497,000013: ## Reference: pp. 505-510
021498,000014: ## Assembler: yaYUL
021499,000015: ## Contact: Ron Burkey <info@sandroid.org>.
021500,000016: ## Website: www.ibiblio.org/apollo/index.html
021501,000017: ## Mod history: 2019-07-30 MAS Created from Comanche 55.
021502,000018:
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Page 505
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021504,000020: 34,2002 BANK 34
021505,000021: 31,2000 SETLOC R31
021506,000022: 31,2000 BANK
021507,000023:
021508,000024: 31,2000 COUNT* $$/R31
021509,000025:
021510,000026: 31,2000 35057 R31CALL CAF PRIO3
021511,000027: 31,2001 05147 TC FINDVAC
021512,000028: 31,2002 E4,1770 EBANK= SUBEXIT
021513,000029: 31,2002 02032 62064 2CADR V83CALL
021514,000030:
021515,000031: 31,2004 35041 DSPDELAY CAF 1SEC
021516,000032: 31,2005 04662 TC BANKCALL
021517,000033: 31,2006 01732 CADR DELAYJOB
021518,000034: 31,2007 31044 CA EXTVBACT
021519,000035: 31,2010 75004 MASK BIT12
021520,000036: 31,2011 00006 EXTEND
021521,000037: 31,2012 12004 BZF DSPDELAY
021522,000038:
021523,000039: 31,2013 30105 DISPN5X CA FLAGWRD9 # TEST R31FLAG (IN SUNDANCE R31FLAG WILL
021524,000040: 31,2014 75014 MASK BIT4 # ALWAYS BE SET AS R34 DOES NOT EXIST)
021525,000041: 31,2015 00006 EXTEND
021526,000042: 31,2016 12021 BZF +3
021527,000043: 31,2017 32136 CAF V16N54 # R31 USE NOUN 54
021528,000044: 31,2020 02022 TC +2
021529,000045: 31,2021 32137 CAF V16N53 # R34 USE NOUN 53
021530,000046: 31,2022 04662 TC BANKCALL
021531,000047: 31,2023 20561 CADR GOMARKF
021532,000048: 31,2024 05625 TC B5OFF
021533,000049: 31,2025 05625 TC B5OFF
021534,000050: 31,2026 12013 TCF DISPN5X
021535,000051:
021536,000052: 31,2027 06006 V83 TC INTPRET
021537,000053: 31,2030 77650 GOTO
021538,000054: 31,2031 62171 HAVEBASE # INTEG STATE VECTORS
021539,000055: 31,2032 06006 V83CALL TC INTPRET
021540,000056: 31,2033 77650 GOTO
021541,000057: 31,2034 62140 STATEXTP # EXTRAPOLATE STATE VECTORS
021542,000058: 31,2035 52375 COMPDISP VLOAD VSU
021543,000059: 31,2036 00001 RATT
021544,000060: 31,2037 02327 RONE
021545,000061: 31,2040 51406 PUSH ABVAL # RATT-RONE TO 0D PD= 6
021546,000062: 31,2041 02321 STORE RANGE # METERS B-29
021547,000063: 31,2042 77301 NORM VLOAD
021548,000064: 31,2043 00047 X1 # RATT-RONE PD= 0
021549,000065: 31,2044 77762 VSR1
021550,000066: 31,2045 53457 VSL* UNIT
021551,000067: 31,2046 20201 0,1
021552,000068: 31,2047 52315 PDVL VSU # UNIT(LOS) TO 0D PD= 6
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Page 506
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021554,000070: 31,2050 00007 VATT
021555,000071: 31,2051 02335 VONE
021556,000072: 31,2052 77641 DOT # (VATT-VONE).UNIT(LOS) PD= 0
021557,000073: 31,2053 77752 SL1
021558,000074: 31,2054 36323 STCALL RRATE # RANGE RATE M/CS B-7
021559,000075: 31,2055 47477 CDUTRIG # TO INITIALIZE FOR *NBSM*
021560,000076: 31,2056 77624 CALL
021561,000077: 31,2057 62311 R34LOS # NOTE. PDL MUST = 0.
021562,000078: 31,2060 53575 R34ANG VLOAD UNIT
021563,000079: 31,2061 02327 RONE
021564,000080: 31,2062 77715 PDVL # UR TO 0D PD= 6
021565,000081: 31,2063 15333 THISAXIS # UNITX FOR CM, UNITZ FOR LM
021566,000082: 31,2064 77214 BON VLOAD # CHK R31FLAG. ON=R31 THETA, OFF=R34 PHI
021567,000083: 31,2065 04713 R31FLAG
021568,000084: 31,2066 62070 +2 # R31-THETA
021569,000085: 31,2067 00015 12D
021570,000086: 31,2070 77624 CALL
021571,000087: 31,2071 47646 *NBSM*
021572,000088: 31,2072 41505 VXM PUSH # UXORZ TO 6D PD=12D
021573,000089: 31,2073 01736 REFSMMAT
021574,000090: 31,2074 72431 VPROJ VSL2
021575,000091: 31,2075 00001 0D
021576,000092: 31,2076 53445 BVSU UNIT
021577,000093: 31,2077 00007 6D
021578,000094: 31,2100 47315 PDVL VXV # UP/2 TO 12D PD=18D
021579,000095: 31,2101 02327 RONE
021580,000096: 31,2102 02335 VONE
021581,000097: 31,2103 47256 UNIT VXV
021582,000098: 31,2104 02327 RONE
021583,000099: 31,2105 63241 DOT PDVL # SIGN TO 12D, UP/2 TO MPAC PD=18D
021584,000100: 31,2106 00015 12D
021585,000101: 31,2107 50372 VSL1 DOT # UP.UXORZ
021586,000102: 31,2110 00007 6D
021587,000103: 31,2111 72565 SIGN SL1
021588,000104: 31,2112 00015 12D
021589,000105: 31,2113 77726 ACOS
021590,000106: 31,2114 26325 STOVL RTHETA
021591,000107: 31,2115 02327 RONE
021592,000108: 31,2116 51041 DOT BPL
021593,000109: 31,2117 00007 6D
021594,000110: 31,2120 62125 +5
021595,000111: 31,2121 44345 DLOAD BDSU # IF UXORZ.R NEG, RTHETA = 1 - RTHETA
021596,000112: 31,2122 02325 RTHETA
021597,000113: 31,2123 15343 DPPOSMAX
021598,000114: 31,2124 02325 STORE RTHETA # RTHETA BETWEEN 0 AND 1 REV.
021599,000115: 31,2125 77776 EXIT
021600,000116: 31,2126 35013 CAF BIT5 # HAVE WE BEEN ANSWERED
021601,000117: 31,2127 71044 MASK EXTVBACT
021602,000118: 31,2130 00006 EXTEND
021603,000119: 31,2131 15534 BZF ENDEXT # YES, DIE
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Page 507
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021605,000121: 31,2132 41044 CS EXTVBACT
021606,000122: 31,2133 75004 MASK BIT12
021607,000123: 31,2134 27044 ADS EXTVBACT
021608,000124:
021609,000125: 31,2135 12027 TCF V83
021610,000126: 31,2136 04066 V16N54 VN 1654
021611,000127: 31,2137 04065 V16N53 VN 1653
021612,000128:
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Page 508
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021614,000130: # STATEXTP DOES AN INITIAL PRECISION EXTRAPOLATION OF THE
021615,000131: # LEM STATE VECTOR TO PRESENT TIME OR TO PIPTIME IF AV G
021616,000132: # IS ON AND SAVES AS BASE VECTOR. IF AV G IS ON RN + VN
021617,000133: # ARE USED AS THE CM STATE VECTOR AND THE INITIAL R RDOT
021618,000134: # RTHETA ARE COMPUTED WITH NO FURTHER INTEGRATION. IF AV
021619,000135: # G IS OFF A PRECISION EXTRAPOLATION IS MADE OF THE CM
021620,000136: # STATE VECTOR TO PRESENT TIME AND.....
021621,000137:
021622,000138: # THE CM + LM STATE VECTORS ARE INTEGRATED TO PRES TIME
021623,000139: # USING PRECISION OR CONIC AS SURFFLAG IS SET OR CLEAR.
021624,000140:
021625,000141: # IF AV G IS ON THEN SUBSEQUENT PASSES WILL PROVIDE
021626,000142: # USE OF RN + VN AS CM STATE VECTOR AND THE LM STATE
021627,000143: # VECTOR WILL BE PRECISION INTEGRATED USING LEMPREC
021628,000144:
021629,000145: # IF SURFFLAG IS SET.
021630,000146: # CM STATE VECTOR RONE VONE + LM STATE VECTOR RATT
021631,000147: # VATT ARE USED IN COMPUTING R RDOT RTHETA.
021632,000148:
021633,000149:
021634,000150: 31,2140 43034 STATEXTP RTB BOF # INITIAL INTEGRATION
021635,000151: 31,2141 45510 LOADTIME
021636,000152: 31,2142 03751 V37FLAG
021637,000153: 31,2143 62146 +3 # AV G OFF, USE PRES TIME
021638,000154: 31,2144 77624 CALL
021639,000155: 31,2145 62273 GETRVN # ON, USE RN VN PIPTIME
021640,000156: 31,2146 02343 STORE BASETIME # PRES TIME OR PIPTIME
021641,000157: 31,2147 34041 STCALL TDEC1
021642,000158: 31,2150 27105 LEMPREC
021643,000159: 31,2151 77775 VLOAD # BASE VECTOR, LM
021644,000160: 31,2152 00017 RATT1
021645,000161: 31,2153 26225 STOVL BASEOTP # POS.
021646,000162: 31,2154 00025 VATT1
021647,000163: 31,2155 02241 STORE BASEOTV # VEL.
021648,000164: 31,2156 71214 BON DLOAD
021649,000165: 31,2157 03711 V37FLAG
021650,000166: 31,2160 62035 COMPDISP # COMPUTE R RDOT RTHETA FROM
021651,000167: # RONE(RN) VONE(VN) RATT+VATT(LEMPREC)
021652,000168: 31,2161 00015 TAT
021653,000169: 31,2162 34041 STCALL TDEC1
021654,000170: 31,2163 27071 CSMPREC
021655,000171: 31,2164 77775 VLOAD # BASE VECTOR, CM
021656,000172: 31,2165 00017 RATT1
021657,000173: 31,2166 26255 STOVL BASETHP # POS.
021658,000174: 31,2167 00025 VATT1
021659,000175: 31,2170 02263 STORE BASETHV # VEL.
021660,000176: 31,2171 47014 HAVEBASE BON RTB # SUBSEQUENT INTEGRATIONS
021661,000177: 31,2172 03711 V37FLAG
021662,000178: 31,2173 62256 GETRVN5
021663,000179: 31,2174 45510 LOADTIME
021664,000180: 31,2175 34041 STCALL TDEC1 # AV G OFF. SET INTEG. OF CM
021665,000181: 31,2176 27442 INTSTALL
021666,000182: 31,2177 43175 VLOAD CLEAR
021667,000183: 31,2200 02255 BASETHP
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Page 509
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021669,000185: 31,2201 00263 MOONFLAG
021670,000186: 31,2202 25535 STOVL RCV
021671,000187: 31,2203 02263 BASETHV
021672,000188: 31,2204 15543 STODL VCV
021673,000189: 31,2205 02343 BASETIME
021674,000190: 31,2206 43014 BOF SET # GET APPROPRIATE MOONFLAG SETTING
021675,000191: 31,2207 04343 MOONTHIS
021676,000192: 31,2210 62212 +2
021677,000193: 31,2211 00063 MOONFLAG
021678,000194: 31,2212 77614 CLEAR
021679,000195: 31,2213 01673 INTYPFLG
021680,000196: 31,2214 43014 BON SET
021681,000197: 31,2215 04307 SURFFLAG
021682,000198: 31,2216 62220 +2 # PREC. IF LM DOWN
021683,000199: 31,2217 01473 INTYPFLG # CONIC IF LM NOT DOWN
021684,000200: 31,2220 35517 STCALL TET
021685,000201: 31,2221 27135 INTEGRVS # INTEGRATION --- AT LAST---
021686,000202: 31,2222 77775 VLOAD
021687,000203: 31,2223 00001 RATT
021688,000204: 31,2224 26327 STOVL RONE
021689,000205: 31,2225 00007 VATT
021690,000206: 31,2226 16335 STODL VONE # GET SET FOR CONIC EXTRAP.,OTHER
021691,000207: 31,2227 00015 TAT
021692,000208: 31,2230 45014 BON CALL
021693,000209: 31,2231 04307 SURFFLAG
021694,000210: 31,2232 62267 GETRVN6 # LEMPREC IF LM DOWN
021695,000211: 31,2233 27442 INTSTALL # ..CONIC IF NOT DOWN
021696,000212: 31,2234 77614 SET
021697,000213: 31,2235 01473 INTYPFLG
021698,000214: 31,2236 00041 OTHINT STORE TDEC1 # ENTERED IF AV G ON TO INTEG LM
021699,000215: 31,2237 43175 VLOAD CLEAR
021700,000216: 31,2240 02225 BASEOTP
021701,000217: 31,2241 00263 MOONFLAG
021702,000218: 31,2242 25535 STOVL RCV
021703,000219: 31,2243 02241 BASEOTV
021704,000220: 31,2244 15543 STODL VCV
021705,000221: 31,2245 02343 BASETIME
021706,000222: 31,2246 43014 BOF SET
021707,000223: 31,2247 04343 MOONTHIS
021708,000224: 31,2250 62252 +2
021709,000225: 31,2251 00063 MOONFLAG
021710,000226: 31,2252 35517 STCALL TET
021711,000227: 31,2253 27135 INTEGRVS
021712,000228: 31,2254 77650 GOTO
021713,000229: 31,2255 62035 COMPDISP # COMPUTE R RDOT RTHETA
021714,000230: 31,2256 77624 GETRVN5 CALL # AV G ON
021715,000231: 31,2257 62273 GETRVN
021716,000232: 31,2260 45014 BON CALL
021717,000233: 31,2261 04307 SURFFLAG
021718,000234: 31,2262 62267 GETRVN6 # LM DOWN, LMPREC
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Page 510
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021720,000236: 31,2263 27442 INTSTALL
021721,000237: 31,2264 52014 CLEAR GOTO
021722,000238: 31,2265 01673 INTYPFLG
021723,000239: 31,2266 62236 OTHINT
021724,000240: 31,2267 34041 GETRVN6 STCALL TDEC1
021725,000241: 31,2270 27105 LEMPREC
021726,000242: 31,2271 77650 GOTO
021727,000243: 31,2272 62035 COMPDISP # COMPUTE R RDOT RTHETA
021728,000244: 31,2273 77620 GETRVN STQ
021729,000245: 31,2274 00000 0D
021730,000246: 31,2275 52175 VLOAD GOTO # AV G ON, RONE = RN VONE = VN
021731,000247: 31,2276 01171 RN # AND USE PIPTIME
021732,000248: 31,2277 62300 +1
021733,000249: 31,2300 36327 STCALL RONE
021734,000250: 31,2301 62302 +1
021735,000251: 31,2302 52175 VLOAD GOTO
021736,000252: 31,2303 01177 VN
021737,000253: 31,2304 62305 +1
021738,000254: 31,2305 16335 STODL VONE
021739,000255: 31,2306 01205 PIPTIME
021740,000256: 31,2307 77650 GOTO
021741,000257: 31,2310 00000 0D
021742,000258: 31,2000 SETLOC R34
021743,000259: 31,2000 BANK
021744,000260: 31,2311 77776 R34LOS EXIT
021745,000261: 31,2312 30036 CA CDUS
021746,000262: 31,2313 50120 INDEX FIXLOC
021747,000263: 31,2314 54011 TS 9D
021748,000264: 31,2315 30035 CA CDUT
021749,000265: 31,2316 50120 INDEX FIXLOC
021750,000266: 31,2317 54013 TS 11D
021751,000267: 31,2320 30120 CA FIXLOC
021752,000268: 31,2321 66211 AD SIX
021753,000269: 31,2322 40000 COM
021754,000270: 31,2323 50120 INDEX FIXLOC
021755,000271: 31,2324 54046 TS X1
021756,000272: 31,2325 06006 TC INTPRET
021757,000273: 31,2326 77624 CALL
021758,000274: 31,2327 46000 SXTNB
021759,000275: 31,2330 34015 STCALL 12D
021760,000276: 31,2331 62060 R34ANG
End of include-file R31.agc. Parent file is MAIN.agc