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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064140,000002: ## Copyright: Public domain.
064141,000003: ## Filename: RTB_OP_CODES.agc
064142,000004: ## Purpose: A section of Comanche revision 051.
064143,000005: ## It is part of the reconstructed source code for the
064144,000006: ## original release of the flight software for the Command
064145,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
064146,000008: ## The code has been recreated from a copy of Comanche 055. It
064147,000009: ## has been adapted such that the resulting bugger words
064148,000010: ## exactly match those specified for Comanche 51 in NASA drawing
064149,000011: ## 2021153D, which gives relatively high confidence that the
064150,000012: ## reconstruction is correct.
064151,000013: ## Reference: pp. 1508-1516
064152,000014: ## Assembler: yaYUL
064153,000015: ## Contact: Ron Burkey <info@sandroid.org>.
064154,000016: ## Website: www.ibiblio.org/apollo/index.html
064155,000017: ## Mod history: 2019-07-30 MAS Created from Comanche 55, and removed R-2
064156,000018: ## lunar potential model code.
064157,000019: ## 2020-12-13 RSB Added justifying annotations for Mike's
064158,000020: ## reconstruction steps.
064159,000021:
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Page 1508
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064161,000023: 22,3510 BANK 22
064162,000024: 22,2000 SETLOC RTBCODES
064163,000025: 22,2000 BANK
064164,000026:
064165,000027: 22,3510 E5,1713 EBANK= XNB
064166,000028: 22,3510 COUNT* $$/RTB
064167,000029:
064168,000030: # LOAD TIME2, TIME1 INTO MPAC:
064169,000031:
064170,000032: 22,3510 00006 LOADTIME EXTEND
064171,000033: 22,3511 30025 DCA TIME2
064172,000034: 22,3512 16024 TCF SLOAD2
064173,000035:
064174,000036: # CONVERT THE SINGLE PRECISION 2'S COMPLEMENT NUMBER ARRIVING IN MPAC (SCALED IN HALF-REVOLUTIONS) TO A
064175,000037: # DP 1'S COMPLEMENT NUMBER SCALED IN REVOLUTIONS.
064176,000038:
064177,000039: 22,3513 10154 CDULOGIC CCS MPAC
064178,000040: 22,3514 35021 CAF ZERO
064179,000041: 22,3515 13520 TCF +3
064180,000042: 22,3516 13517 NOOP
064181,000043: 22,3517 45002 CS HALF
064182,000044:
064183,000045: 22,3520 54155 TS MPAC +1
064184,000046: 22,3521 35021 CAF ZERO
064185,000047: 22,3522 56154 XCH MPAC
064186,000048: 22,3523 00006 EXTEND
064187,000049: 22,3524 75002 MP HALF
064188,000050: 22,3525 20155 DAS MPAC
064189,000051: 22,3526 16030 TCF DANZIG # MODE IS ALREADY AT DOUBLE-PRECISION
064190,000052:
064191,000053: # READ THE PIPS INTO MPAC WITHOUT CHANGING THEM:
064192,000054:
064193,000055: 22,3527 00004 READPIPS INHINT
064194,000056: 22,3530 30037 CA PIPAX
064195,000057: 22,3531 54154 TS MPAC
064196,000058: 22,3532 30040 CA PIPAY
064197,000059: 22,3533 54157 TS MPAC +3
064198,000060: 22,3534 30041 CA PIPAZ
064199,000061: 22,3535 00003 RELINT
064200,000062: 22,3536 54161 TS MPAC +5
064201,000063:
064202,000064: 22,3537 35021 CAF ZERO
064203,000065: 22,3540 54155 TS MPAC +1
064204,000066: 22,3541 54160 TS MPAC +4
064205,000067: 22,3542 54162 TS MPAC +6
064206,000068: 22,3543 16470 VECMODE TCF VMODE
064207,000069:
064208,000070: # FORCE TP SIGN AGREEMENT IN MPAC:
064209,000071:
064210,000072: 22,3544 07226 SGNAGREE TC TPAGREE
064211,000073:
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Page 1509
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064213,000075:
064214,000076: 22,3545 16030 TCF DANZIG
064215,000077:
064216,000078: # CONVERT THE DP 1'S COMPLEMENT ANGLE SCALED IN REVOLUTIONS TO A SINGLE PRECISION 2'S COMPLEMENT ANGLE
064217,000079: # SCALED IN HALF-REVOLUTIONS.
064218,000080:
064219,000081: 22,3546 03576 1STO2S TC 1TO2SUB
064220,000082: 22,3547 35021 CAF ZERO
064221,000083: 22,3550 54155 TS MPAC +1
064222,000084: 22,3551 16027 TCF NEWMODE
064223,000085:
064224,000086: # DO 1STO2S ON A VECTOR OF ANGLES:
064225,000087:
064226,000088: 22,3552 03576 V1STO2S TC 1TO2SUB # ANSWER ARRIVES IN A AND MPAC.
064227,000089:
064228,000090: 22,3553 52162 DXCH MPAC +5
064229,000091: 22,3554 52155 DXCH MPAC
064230,000092: 22,3555 03576 TC 1TO2SUB
064231,000093: 22,3556 54156 TS MPAC +2
064232,000094:
064233,000095: 22,3557 52160 DXCH MPAC +3
064234,000096: 22,3560 52155 DXCH MPAC
064235,000097: 22,3561 03576 TC 1TO2SUB
064236,000098: 22,3562 54155 TS MPAC +1
064237,000099:
064238,000100: 22,3563 30161 CA MPAC +5
064239,000101: 22,3564 54154 TS MPAC
064240,000102:
064241,000103: 22,3565 35017 TPMODE CAF ONE # MODE IS TP.
064242,000104: 22,3566 16027 TCF NEWMODE
064243,000105:
064244,000106: # V1STO2S FOR 2 COMPONENT VECTOR. USED BY RR.
064245,000107:
064246,000108: 22,3567 03576 2V1STO2S TC 1TO2SUB
064247,000109: 22,3570 52160 DXCH MPAC +3
064248,000110: 22,3571 52155 DXCH MPAC
064249,000111: 22,3572 03576 TC 1TO2SUB
064250,000112: 22,3573 54001 TS L
064251,000113: 22,3574 30157 CA MPAC +3
064252,000114: 22,3575 16024 TCF SLOAD2
064253,000115:
064254,000116: # SUBROUTINE TO DO DOUBLING AND 1'S TO 2'S CONVERSION:
064255,000117:
064256,000118: 22,3576 52155 1TO2SUB DXCH MPAC # FINAL MPAC +1 UNSPECIFIED.
064257,000119: 22,3577 20001 DDOUBL
064258,000120: 22,3600 10000 CCS A
064259,000121: 22,3601 65017 AD ONE
064260,000122: 22,3602 13604 TCF +2
064261,000123: 22,3603 40000 COM # THIS WAS REVERSE OF MSU.
064262,000124:
064263,000125: 22,3604 54154 TS MPAC # AND SKIP ON OVERFLOW.
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Page 1510
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064265,000127: 22,3605 00002 TC Q
064266,000128:
064267,000129: 22,3606 50000 INDEX A # OVERFLOW UNCORRECT AND IN MSU.
064268,000130: 22,3607 35000 CAF LIMITS
064269,000131: 22,3610 26154 ADS MPAC
064270,000132: 22,3611 00002 TC Q
064271,000133:
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Page 1511
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064273,000135: # SUBROUTINE TO INCREMENT CDUS
064274,000136:
064275,000137: 22,3612 33625 INCRCDUS CAF LOCTHETA
064276,000138: 22,3613 54130 TS BUF # PLACE ADRES(THETA) IN BUF.
064277,000139: 22,3614 30154 CAE MPAC # INCREMENT IN 1S COMPL.
064278,000140: 22,3615 03626 TC CDUINC
064279,000141:
064280,000142: 22,3616 24130 INCR BUF
064281,000143: 22,3617 30157 CAE MPAC +3
064282,000144: 22,3620 03626 TC CDUINC
064283,000145:
064284,000146: 22,3621 24130 INCR BUF
064285,000147: 22,3622 30161 CAE MPAC +5
064286,000148: 22,3623 03626 TC CDUINC
064287,000149:
064288,000150: 22,3624 13543 TCF VECMODE
064289,000151:
064290,000152: 22,3625 01155 LOCTHETA ADRES THETAD
064291,000153:
064292,000154: # THE FOLLOWING ROUTINE INCREMENTS IN 2S COMPLEMENT THE REGISTER WHOSE ADDRESS IS IN BUF BY THE 1S COMPL.
064293,000155: # QUANTITY FOUND IN TEM2. THIS MAY BE USED TO INCREMENT DESIRED IMU AND OPTICS CDU ANGLES OR ANY OTHER 2S COMPL.
064294,000156: # (+0 UNEQUAL TO -0) QUANTITY. MAY BE CALLED BY BANKCALL/SWCALL.
064295,000157:
064296,000158: 22,3626 54142 CDUINC TS TEM2 # 1S COMPL. QUANT. ARRIVES IN ACC. STORE IT
064297,000159: 22,3627 50130 INDEX BUF
064298,000160: 22,3630 10000 CCS 0 # CHANGE 2S COMPL. ANGLE (IN BUF) INTO 1S
064299,000161: 22,3631 65017 AD ONE
064300,000162: 22,3632 13636 TCF +4
064301,000163: 22,3633 65017 AD ONE
064302,000164: 22,3634 65017 AD ONE # OVERFLOW HERE IF 2S COMPL. IS 180 DEG.
064303,000165: 22,3635 40000 COM
064304,000166:
064305,000167: 22,3636 60142 AD TEM2 # SULT MOVES FROM 2ND TO 3D QUAD. (OR BACK)
064306,000168: 22,3637 10000 CCS A # BACK TO 2S COMPL.
064307,000169: 22,3640 65017 AD ONE
064308,000170: 22,3641 13643 TCF +2
064309,000171: 22,3642 40000 COM
064310,000172: 22,3643 54142 TS TEM2 # STORE 14BIT QUANTITY WITH PRESENT SIGN
064311,000173: 22,3644 13650 TCF +4
064312,000174: 22,3645 50000 INDEX A # SIGN.
064313,000175: 22,3646 35000 CAF LIMITS # FIX IT, BY ADDING IN 37777 OR 40000
064314,000176: 22,3647 60142 AD TEM2
064315,000177:
064316,000178: 22,3650 50130 INDEX BUF
064317,000179: 22,3651 54000 TS 0 # STORE NEW ANGLE IN 2S COMPLEMENT.
064318,000180: 22,3652 00002 TC Q
064319,000181:
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Page 1512
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064321,000183: # RTB TO TORQUE GYROS, EXCEPT FOR THE CALL TO IMUSTALL. ECADR OF COMMANDS ARRIVES IN X1.
064322,000184:
064323,000185: 22,3653 50120 PULSEIMU INDEX FIXLOC # ADDRESS OF GYRO COMMANDS SHOULD BE IN X1
064324,000186: 22,3654 30046 CA X1
064325,000187: 22,3655 04662 TC BANKCALL
064326,000188: 22,3656 17206 CADR IMUPULSE
064327,000189: 22,3657 16030 TCF DANZIG
064328,000190:
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Page 1513
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064330,000192: # EACH ROUTINE TAKES A 3X3 MATRIX STORED IN DOUBLE PRECISION IN A FIXED AREA OF ERASABLE MEMORY AND REPLACES IT
064331,000193: # WITH THE TRANSPOSE MATRIX. TRANSP1 USES LOCATIONS XNB+0,+1 THROUGH XNB+16D, 17D AND TRANSP2 USES LOCATIONS
064332,000194: # XNB1+0,+1 THROUGH XNB1+16D, 17D. EACH MATRIX IS STORED BY ROWS.
064333,000195:
064334,000196: 22,3660 02713 XNBEB ECADR XNB
064335,000197: 22,3661 02554 XNB1EB ECADR XNB1
064336,000198:
064337,000199: 22,3662 E5,1713 EBANK= XNB
064338,000200:
064339,000201: 22,3662 33660 TRANSP1 CAF XNBEB
064340,000202: 22,3663 54003 TS EBANK
064341,000203: 22,3664 53716 DXCH XNB +2
064342,000204: 22,3665 53722 DXCH XNB +6
064343,000205: 22,3666 53716 DXCH XNB +2
064344,000206:
064345,000207: 22,3667 53720 DXCH XNB +4
064346,000208: 22,3670 53730 DXCH XNB +12D
064347,000209: 22,3671 53720 DXCH XNB +4
064348,000210:
064349,000211: 22,3672 53726 DXCH XNB +10D
064350,000212: 22,3673 53732 DXCH XNB +14D
064351,000213: 22,3674 53726 DXCH XNB +10D
064352,000214: 22,3675 16030 TCF DANZIG
064353,000215: 22,3676 E5,1554 EBANK= XNB1
064354,000216:
064355,000217: 22,3676 33661 TRANSP2 CAF XNB1EB
064356,000218: 22,3677 54003 TS EBANK
064357,000219: 22,3700 53557 DXCH XNB1 +2
064358,000220: 22,3701 53563 DXCH XNB1 +6
064359,000221: 22,3702 53557 DXCH XNB1 +2
064360,000222:
064361,000223: 22,3703 53561 DXCH XNB1 +4
064362,000224: 22,3704 53571 DXCH XNB1 +12D
064363,000225: 22,3705 53561 DXCH XNB1 +4
064364,000226:
064365,000227: 22,3706 53567 DXCH XNB1 +10D
064366,000228: 22,3707 53573 DXCH XNB1 +14D
064367,000229: 22,3710 53567 DXCH XNB1 +10D
064368,000230: 22,3711 16030 TCF DANZIG
064369,000231:
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Page 1514
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064371,000233: # THE SUBROUTINE SIGNMPAC SETS C(MPAC, MPAC +1) TO SIGN(MPAC).
064372,000234: # FOR THIS, ONLY THE CONTENTS OF MPAC ARE EXAMINED. ALSO +0 YIELDS POSMAX AND -0 YIELDS NEGMAX.
064373,000235:
064374,000236: # ENTRY MAY BE BY EITHER OF THE FOLLOWING:
064375,000237: # 1. LIMIT THE SIZE OF MPAC ON INTERPRETIVE OVERFLOW:
064376,000238: # ENTRY: BOVB
064377,000239: # SIGNMPAC
064378,000240: # 2. GENERATE IN MPAC THE SIGNUM FUNCTION OF MPAC:
064379,000241: # ENTRY: RTB
064380,000242: # SIGNMPAC
064381,000243: # IN EITHER CASE, RETURN IS TO THE NEXT INTERPRETIVE INSTRUCTION IN THE CALLING SEQUENCE.
064382,000244:
064383,000245: 22,3712 00006 SIGNMPAC EXTEND
064384,000246: 22,3713 34777 DCA DPOSMAX
064385,000247: 22,3714 52155 DXCH MPAC
064386,000248: 22,3715 10000 CCS A
064387,000249: 22,3716 35021 DPMODE CAF ZERO # SETS MPAC +2 TO ZERO IN THE PROCESS
064388,000250: 22,3717 16026 TCF SLOAD2 +2
064389,000251: 22,3720 13721 TCF +1
064390,000252: 22,3721 00006 EXTEND
064391,000253: 22,3722 44777 DCS DPOSMAX
064392,000254: 22,3723 16024 TCF SLOAD2
064393,000255:
064394,000256: # RTB OP CODE NORMUNIT IS LIKE INTERPRETIVE INSTRUCTION UNIT, EXCEPT THAT IT CAN BE DEPENDED ON NOT TO BLOW
064395,000257: # UP WHEN THE VECTOR BEING UNITIZED IS VERY SMALL -- IT WILL BLOW UP WHEN ALL COMPONENTS ARE ZERO. IF NORMUNIT
064396,000258: # IS USED AND THE UPPER ORDER HALVES OF ALL COMPONENTS ARE ZERO, THE MAGNITUDE RETURNED IN 36D WILL BE TOO LARGE
064397,000259: # BY A FACTOR OF 2(13) AND THE SQUARED MAGNITUDE RETURNED AT 34D WILL BE TOO BIG BY A FACTOR OF 2(26).
064398,000260:
064399,000261: 22,3724 35017 NORMUNX1 CAF ONE
064400,000262: 22,3725 13727 TCF NORMUNIT +1
064401,000263: 22,3726 35021 NORMUNIT CAF ZERO
064402,000264: 22,3727 60120 AD FIXLOC
064403,000265: 22,3730 54156 TS MPAC +2
064404,000266: 22,3731 04662 TC BANKCALL # GET SIGN AGREEMENT IN ALL COMPONENTS
064405,000267: 22,3732 01010 CADR VECAGREE
064406,000268: 22,3733 10154 CCS MPAC
064407,000269: 22,3734 13770 TCF NOSHIFT
064408,000270: 22,3735 13737 TCF +2
064409,000271: 22,3736 13770 TCF NOSHIFT
064410,000272: 22,3737 10157 CCS MPAC +3
064411,000273: 22,3740 13770 TCF NOSHIFT
064412,000274: 22,3741 13743 TCF +2
064413,000275: 22,3742 13770 TCF NOSHIFT
064414,000276: 22,3743 10161 CCS MPAC +5
064415,000277: 22,3744 13770 TCF NOSHIFT
064416,000278: 22,3745 13747 TCF +2
064417,000279: 22,3746 13770 TCF NOSHIFT
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Page 1515
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064419,000281: 22,3747 30155 CA MPAC +1 # SHIFT ALL COMPONENTS LEFT 13
064420,000282: 22,3750 00006 EXTEND
064421,000283: 22,3751 75002 MP BIT14
064422,000284: 22,3752 20155 DAS MPAC # DAS GAINS A LITTLE ACCURACY
064423,000285: 22,3753 30160 CA MPAC +4
064424,000286: 22,3754 00006 EXTEND
064425,000287: 22,3755 75002 MP BIT14
064426,000288: 22,3756 20160 DAS MPAC +3
064427,000289: 22,3757 30162 CA MPAC +6
064428,000290: 22,3760 00006 EXTEND
064429,000291: 22,3761 75002 MP BIT14
064430,000292: 22,3762 20162 DAS MPAC +5
064431,000293: 22,3763 35025 CAF THIRTEEN
064432,000294: 22,3764 50156 INDEX MPAC +2
064433,000295: 22,3765 54045 TS 37D
064434,000296: 22,3766 04701 OFFTUNIT TC POSTJUMP
064435,000297: 22,3767 01024 CADR UNIT +1 # SKIP THE "TC VECAGREE" DONE AT UNIT
064436,000298:
064437,000299: 22,3770 35021 NOSHIFT CAF ZERO
064438,000300: 22,3771 13764 TCF OFFTUNIT -2
064439,000301:
064440,000302: # RTB VECSGNAG ... FORCES SIGN AGREEMENT OF VECTOR IN MPAC.
064441,000303:
064442,000304: 22,3772 04662 VECSGNAG TC BANKCALL
064443,000305: 22,3773 01010 CADR VECAGREE
064444,000306: 22,3774 06030 TC DANZIG
064445,000307:
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Page 1516
Reconstruction: As described in some detail in
an annotation in the ORBITAL INTEGRATION
log section, the principal difference between Comanche 51 and Comanche 55 is that
the latter contains "R-2 Lunar Potential Model" code identical to that from the
ORBITAL INTEGRATION log section of Luminary 69/2 (Apollo 10 LM final software release).
However, two of the functions of that code, QUALITY1 and QUALITY2, were instead placed
at the end of Comanche 55's RTB OP CODES log section. Presumably this was done for
practical reasons, in that it allowed remanufacturing a single core-rope module (B2)
in upgrading Comanche 51 to 55. Regardless of the intention, Comanche 51 has no
R-2 model, so that code has been removed.
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064458,000320:
End of include-file RTB_OP_CODES.agc. Parent file is MAIN.agc