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.
|
060422,000002: ## Copyright: Public domain.
060423,000003: ## Filename: RTB_OP_CODES.agc
060424,000004: ## Purpose: A section of Skylark revision 048.
060425,000005: ## It is part of the source code for the Apollo Guidance Computer (AGC)
060426,000006: ## for Skylab-2, Skylab-3, Skylab-4, and ASTP. No original listings of
060427,000007: ## this software are available; instead, this file was created via
060428,000008: ## disassembly of dumps of the core rope modules actually flown on
060429,000009: ## Skylab-2. Access to these modules was provided by the New Mexico
060430,000010: ## Museum of Space History.
060431,000011: ## Assembler: yaYUL
060432,000012: ## Contact: Ron Burkey <info@sandroid.org>.
060433,000013: ## Website: www.ibiblio.org/apollo/index.html
060434,000014: ## Mod history: 2023-09-04 MAS Created from Artemis 072.
060435,000015:
060436,000016:
060437,000017: 22,2000 SETLOC RTBCODE1
060438,000018: 22,2000 BANK
060439,000019:
060440,000020: 22,3563 E5,1702 EBANK= XNB
060441,000021: 22,3563 COUNT* $$/RTB
060442,000022:
060443,000023: # LOAD TIME2, TIME1 INTO MPAC:
060444,000024:
060445,000025: 22,3563 00006 LOADTIME EXTEND
060446,000026: 22,3564 30025 DCA TIME2
060447,000027: 22,3565 16024 TCF SLOAD2
060448,000028:
060449,000029: # CONVERT THE SINGLE PRECISION 2'S COMPLEMENT NUMBER ARRIVING IN MPAC (SCALED IN HALF-REVOLUTIONS) TO A
060450,000030: # DP 1'S COMPLEMENT NUMBER SCALED IN REVOLUTIONS.
060451,000031:
060452,000032: 22,3566 10154 CDULOGIC CCS MPAC
060453,000033: 22,3567 35003 CAF ZERO
060454,000034: 22,3570 13573 TCF +3
060455,000035: 22,3571 13572 NOOP
060456,000036: 22,3572 44764 CS HALF
060457,000037:
060458,000038: 22,3573 54155 TS MPAC +1
060459,000039: 22,3574 35003 CAF ZERO
060460,000040: 22,3575 56154 XCH MPAC
060461,000041: 22,3576 00006 EXTEND
060462,000042: 22,3577 74764 MP HALF
060463,000043: 22,3600 20155 DAS MPAC
060464,000044: 22,3601 16030 TCF DANZIG # MODE IS ALREADY AT DOUBLE-PRECISION
060465,000045:
060466,000046: 22,2000 SETLOC RTBCODES
060467,000047: 22,2000 BANK
060468,000048:
060469,000049: 22,3602 COUNT* $$/RTB
060470,000050:
060471,000051: # READ THE PIPS INTO MPAC WITHOUT CHANGING THEM:
060472,000052:
060473,000053: 22,3602 00004 READPIPS INHINT
060474,000054: 22,3603 30037 CA PIPAX
060475,000055: 22,3604 54154 TS MPAC
060476,000056: 22,3605 30040 CA PIPAY
060477,000057: 22,3606 54157 TS MPAC +3
060478,000058: 22,3607 30041 CA PIPAZ
060479,000059: 22,3610 00003 RELINT
060480,000060: 22,3611 54161 TS MPAC +5
060481,000061:
060482,000062: 22,3612 35003 CAF ZERO
060483,000063: 22,3613 54155 TS MPAC +1
060484,000064: 22,3614 54160 TS MPAC +4
060485,000065: 22,3615 54162 TS MPAC +6
060486,000066: 22,3616 16470 VECMODE TCF VMODE
060487,000067:
060488,000068:
060489,000069: # FORCE TP SIGN AGREEMENT IN MPAC:
060490,000070:
060491,000071: 22,3617 07226 SGNAGREE TC TPAGREE
060492,000072: 22,3620 16030 TCF DANZIG
060493,000073:
060494,000074: # CONVERT THE DP 1'S COMPLEMENT ANGLE SCALED IN REVOLUTIONS TO A SINGLE PRECISION 2'S COMPLEMENT ANGLE
060495,000075: # SCALED IN HALF-REVOLUTIONS.
060496,000076:
060497,000077: 22,3621 03642 1STO2S TC 1TO2SUB
060498,000078: 22,3622 35003 CAF ZERO
060499,000079: 22,3623 54155 TS MPAC +1
060500,000080: 22,3624 16027 TCF NEWMODE
060501,000081:
060502,000082: # DO 1STO2S ON A VECTOR OF ANGLES:
060503,000083:
060504,000084: 22,3625 03642 V1STO2S TC 1TO2SUB # ANSWER ARRIVES IN A AND MPAC.
060505,000085:
060506,000086: 22,3626 52162 DXCH MPAC +5
060507,000087: 22,3627 52155 DXCH MPAC
060508,000088: 22,3630 03642 TC 1TO2SUB
060509,000089: 22,3631 54156 TS MPAC +2
060510,000090:
060511,000091: 22,3632 52160 DXCH MPAC +3
060512,000092: 22,3633 52155 DXCH MPAC
060513,000093: 22,3634 03642 TC 1TO2SUB
060514,000094: 22,3635 54155 TS MPAC +1
060515,000095:
060516,000096: 22,3636 30161 CA MPAC +5
060517,000097: 22,3637 54154 TS MPAC
060518,000098:
060519,000099: 22,3640 35001 TPMODE CAF ONE # MODE IS TP.
060520,000100: 22,3641 16027 TCF NEWMODE
060521,000101:
060522,000102: # SUBROUTINE TO DO DOUBLING AND 1'S TO 2'S CONVERSION:
060523,000103:
060524,000104: 22,3642 52155 1TO2SUB DXCH MPAC # FINAL MPAC +1 UNSPECIFIED.
060525,000105: 22,3643 20001 DDOUBL
060526,000106: 22,3644 10000 CCS A
060527,000107: 22,3645 65001 AD ONE
060528,000108: 22,3646 13650 TCF +2
060529,000109: 22,3647 40000 COM # THIS WAS REVERSE OF MSU.
060530,000110:
060531,000111: 22,3650 54154 TS MPAC # AND SKIP ON OVERFLOW.
060532,000112: 22,3651 00002 TC Q
060533,000113:
060534,000114: 22,3652 50000 INDEX A # OVERFLOW UNCORRECT AND IN MSU.
060535,000115: 22,3653 34762 CAF LIMITS
060536,000116: 22,3654 26154 ADS MPAC
060537,000117: 22,3655 00002 TC Q
060538,000118:
060539,000119:
060540,000120: # THE FOLLOWING ROUTINE INCREMENTS IN 2S COMPLEMENT THE REGISTER WHOSE ADDRESS IS IN BUF BY THE 1S COMPL.
060541,000121: # QUANTITY FOUND IN TEM2. THIS MAY BE USED TO INCREMENT DESIRED IMU AND OPTICS CDU ANGLES OR ANY OTHER 2S COMPL.
060542,000122: # (+0 UNEQUAL TO -0) QUANTITY. MAY BE CALLED BY BANKCALL/SWCALL.
060543,000123:
060544,000124: 22,3656 54142 CDUINC TS TEM2 # 1S COMPL.QUANT. ARRIVES IN ACC. STORE IT
060545,000125: 22,3657 50130 INDEX BUF
060546,000126: 22,3660 10000 CCS 0 # CHANGE 2S COMPL. ANGLE(IN BUF)INTO 1S
060547,000127: 22,3661 65001 AD ONE
060548,000128: 22,3662 13666 TCF +4
060549,000129: 22,3663 65001 AD ONE
060550,000130: 22,3664 65001 AD ONE # OVERFLOW HERE IF 2S COMPL. IS 180 DEG.
060551,000131: 22,3665 40000 COM
060552,000132:
060553,000133: 22,3666 60142 AD TEM2 # SULT MOVES FROM 2ND TO 3D QUAD. (OR BACK)
060554,000134: 22,3667 10000 CCS A # BACK TO 2S COMPL.
060555,000135: 22,3670 65001 AD ONE
060556,000136: 22,3671 13673 TCF +2
060557,000137: 22,3672 40000 COM
060558,000138: 22,3673 54142 TS TEM2 # STORE 14BIT QUANTITY WITH PRESENT SIGN
060559,000139: 22,3674 13700 TCF +4
060560,000140: 22,3675 50000 INDEX A # SIGN.
060561,000141: 22,3676 34762 CAF LIMITS # FIX IT, BY ADDING IN 37777 OR 40000
060562,000142: 22,3677 60142 AD TEM2
060563,000143:
060564,000144: 22,3700 50130 INDEX BUF
060565,000145: 22,3701 54000 TS 0 # STORE NEW ANGLE IN 2S COMPLEMENT.
060566,000146: 22,3702 00002 TC Q
060567,000147:
060568,000148:
060569,000149: # RTB TO TORQUE GYROS, EXCEPT FOR THE CALL TO IMUSTALL. ECADR OF COMMANDS ARRIVES IN X1.
060570,000150:
060571,000151: 22,3703 50120 PULSEIMU INDEX FIXLOC # ADDRESS OF GYRO COMMANDS SHOULD BE IN X1
060572,000152: 22,3704 30046 CA X1
060573,000153: 22,3705 04647 TC BANKCALL
060574,000154: 22,3706 17175 CADR IMUPULSE
060575,000155: 22,3707 16030 TCF DANZIG
060576,000156:
060577,000157:
060578,000158: # EACH ROUTINE TAKES A 3X3 MATRIX STORED IN DOUBLE PRECISION IN A FIXED AREA OF ERASABLE MEMORY AND REPLACES IT
060579,000159: # WITH THE TRANSPOSE MATRIX. TRANSP1 USES LOCATIONS XNB+0,+1 THROUGH XNB+16D, 17D AND TRANSP2 USES LOCATIONS
060580,000160: # XNB1+0,+1 THROUGH XNB1+16D, 17D. EACH MATRIX IS STORED BY ROWS.
060581,000161:
060582,000162: 22,3710 02702 XNBEB ECADR XNB
060583,000163: 22,3711 02554 XNB1EB ECADR XNB1
060584,000164:
060585,000165: 22,3712 E5,1702 EBANK= XNB
060586,000166:
060587,000167: 22,3712 33710 TRANSP1 CAF XNBEB
060588,000168: 22,3713 54003 TS EBANK
060589,000169: 22,3714 53705 DXCH XNB +2
060590,000170: 22,3715 53711 DXCH XNB +6
060591,000171: 22,3716 53705 DXCH XNB +2
060592,000172:
060593,000173: 22,3717 53707 DXCH XNB +4
060594,000174: 22,3720 53717 DXCH XNB +12D
060595,000175: 22,3721 53707 DXCH XNB +4
060596,000176:
060597,000177: 22,3722 53715 DXCH XNB +10D
060598,000178: 22,3723 53721 DXCH XNB +14D
060599,000179: 22,3724 53715 DXCH XNB +10D
060600,000180: 22,3725 16030 TCF DANZIG
060601,000181:
060602,000182: 22,3726 E5,1554 EBANK= XNB1
060603,000183:
060604,000184: 22,3726 33711 TRANSP2 CAF XNB1EB
060605,000185: 22,3727 54003 TS EBANK
060606,000186: 22,3730 53557 DXCH XNB1 +2
060607,000187: 22,3731 53563 DXCH XNB1 +6
060608,000188: 22,3732 53557 DXCH XNB1 +2
060609,000189:
060610,000190: 22,3733 53561 DXCH XNB1 +4
060611,000191: 22,3734 53571 DXCH XNB1 +12D
060612,000192: 22,3735 53561 DXCH XNB1 +4
060613,000193:
060614,000194: 22,3736 53567 DXCH XNB1 +10D
060615,000195: 22,3737 53573 DXCH XNB1 +14D
060616,000196: 22,3740 53567 DXCH XNB1 +10D
060617,000197: 22,3741 16030 TCF DANZIG
060618,000198:
060619,000199:
060620,000200: # THE SUBROUTINE SIGNMPAC SETS C(MPAC, MPAC +1) TO SIGN(MPAC).
060621,000201: # FOR THIS, ONLY THE CONTENTS OF MPAC ARE EXAMINED. ALSO +0 YIELDS POSMAX AND -0 YIELDS NEGMAX.
060622,000202:
060623,000203: # ENTRY MAY BE BY EITHER OF THE FOLLOWING:
060624,000204:
060625,000205: # 1. LIMIT THE SIZE OF MPAC ON INTERPRETIVE OVERFLOW:
060626,000206: # ENTRY: BOVB
060627,000207: # SIGNMPAC
060628,000208: # 2. GENERATE IN MPAC THE SIGNUM FUNCTION OF MPAC:
060629,000209: # ENTRY: RTB
060630,000210: # SIGNMPAC
060631,000211:
060632,000212: # IN EITHER CASE, RETURN IS TO THE NEXT INTERPRETIVE INSTRUCTION IN THE CALLING SEQUENCE.
060633,000213:
060634,000214: 22,3742 00006 SIGNMPAC EXTEND
060635,000215: 22,3743 34761 DCA DPOSMAX
060636,000216: 22,3744 52155 DXCH MPAC
060637,000217: 22,3745 10000 CCS A
060638,000218: 22,3746 35003 DPMODE CAF ZERO # SETS MPAC +2 TO ZERO IN THE PROCESS
060639,000219: 22,3747 16026 TCF SLOAD2 +2
060640,000220: 22,3750 13751 TCF +1
060641,000221: 22,3751 00006 EXTEND
060642,000222: 22,3752 44761 DCS DPOSMAX
060643,000223: 22,3753 16024 TCF SLOAD2
060644,000224:
060645,000225:
End of include-file RTB_OP_CODES.agc. Parent file is MAIN.agc