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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008216,000002: ## Copyright: Public domain.
008217,000003: ## Filename: AGS_INITIALIZATION.agc
008218,000004: ## Purpose: A section of LM131 revision 1.
008219,000005: ## It is part of the reconstructed source code for the final
008220,000006: ## release of the flight software for the Lunar Module's (LM)
008221,000007: ## Apollo Guidance Computer (AGC) for Apollo 13. The code has
008222,000008: ## been reconstructed from a listing of Luminary 131 and a dump
008223,000009: ## of a core rope memory module B5, part number 2010802-171,
008224,000010: ## which is the only module different between LM131 revision 1
008225,000011: ## and Luminary 131. The executable generated from this source
008226,000012: ## has been verified against the module dump, so while the names,
008227,000013: ## comments, and ordering may not be exactly correct, the
008228,000014: ## resulting binary is.
008229,000015: ## Reference: pp. 208-212
008230,000016: ## Assembler: yaYUL
008231,000017: ## Contact: Ron Burkey <info@sandroid.org>.
008232,000018: ## Website: www.ibiblio.org/apollo/index.html
008233,000019: ## Mod history: 2022-10-28 MAS Created from Luminary 131.
008234,000020:
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Page 208
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008236,000022:
008237,000023: # PROGRAM NAME: AGS INITIALIZATION (R47)
008238,000024:
008239,000025: # WRITTEN BY: RHODE/KILROY/FOLLETT
008240,000026:
008241,000027: # MOD NO.: 0
008242,000028: # DATE: 23 MARCH 1967
008243,000029: # MOD BY: KILROY
008244,000030:
008245,000031: # MOD NO.: 1
008246,000032: # DATE: 28 OCTOBER 1967
008247,000033: # MOD BY: FOLLETT
008248,000034:
008249,000035: # FUNCT. DESC.: (1) TO PROVIDE THE AGS ABORT ELECTRONICS ASSEMBLY (AEA) WITH THE LEM AND CSM STATE VECTORS
008250,000036: # (POSITION,VELOCITY,TIME) IN LEM IMU COORDINATES BY MEANS OF THE LGC DIGITAL DOWNLINK.
008251,000037:
008252,000038: # (2) TO ZERO THE ICDU, LGC AND AEA GIMBAL ANGLE COUNTERS SIMULTANEOUSLY IN ORDER TO ESTABLISH A
008253,000039: # COMMON ZERO REFERENCE FOR THE MEASUREMENT OF GIMBAL (EULER) ANGLES WHICH DEFINE LEM ATTITUDE
008254,000040:
008255,000041: # (3) TO ESTABLISH THE GROUND ELAPSED TIME OF AEA CLOCK ZERO. (IF AN AEA CLOCK ZERO IS
008256,000042: # REQUESTED DURING THIS PROGRAM
008257,000043:
008258,000044: # LOG SECTION: AGS INITIALIZATION
008259,000045:
008260,000046: # CALLING SEQ: PROGRAM IS ENTERED WHEN ASTRONAUT KEYS V47E ON DSKY.
008261,000047: # R47 MAY BE CALLED AT ANY TIME EXCEPT WHEN ANOTHER EXTENDED VERB IS IN PROGRESS
008262,000048:
008263,000049: # SUBROUTINES
008264,000050: # CALLED:
008265,000051:
008266,000052: # NORMAL EXIT: ENDEXT
008267,000053:
008268,000054: # ALARM/ABORT: ALARM - BAD REFSMMAT - CODE:220
008269,000055: # OPERATOR ERROR IF V47 SELECTED DURING ANOTHER EXTENDED VERB.
008270,000056:
008271,000057: # ERASABLES
008272,000058: # USED: SAMPTIME (2) TIME OF :ENTER: KEYSTROKE
008273,000059: # AGSK (2) GROUND ELAPSED TIME OF THE AEA CLOCK :ZERO:
008274,000060: # AGSBUFF (140) CONTAINS AGS INITIALIZATION DATA (SEE :OUTPUT: BELOW)
008275,000061: # AGSWORD (1) PREVIOUS DOWNLIST SAVED HERE
008276,000062:
008277,000063: 05,2447 E4,1600 EBANK= AGSBUFF
008278,000064:
008279,000065: 40,2000 BANK 40
008280,000066: 32,2000 SETLOC R47
008281,000067: 32,2000 BANK
008282,000068:
008283,000069: 32,2005 COUNT* $$/R47
008284,000070:
008285,000071: 32,2005 34737 AGSINIT CAF REFSMBIT
008286,000072: 32,2006 70077 MASK FLAGWRD3 # CHECK REFSMFLG.
008287,000073: 32,2007 10000 CCS A
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008289,000075: 32,2010 02017 TC REDSPTEM # REFSMMAT IS OK
008290,000076: 32,2011 05567 TC ALARM # REFSMMAT IS BAD
008291,000077: 32,2012 00220 OCT 220
008292,000078: 32,2013 05472 TC ENDEXT
008293,000079:
008294,000080: 32,2014 00006 NEWAGS EXTEND
008295,000081: 32,2015 30014 DCA SAMPTIME # TIME OF THE :ENTER: KEYSTROKE
008296,000082: 32,2016 53421 DXCH AGSK # BECOMES NEW AEA CLOCK :ZERO:
008297,000083:
008298,000084: 32,2017 00006 REDSPTEM EXTEND
008299,000085: 32,2020 31421 DCA AGSK
008300,000086: 32,2021 53051 DXCH DSPTEMX
008301,000087: 32,2022 32172 AGSDISPK CAF V06N16
008302,000088: 32,2023 04616 TC BANKCALL # R1 = 00XXX. HRS., R2 = 000XX MIN.,
008303,000089: 32,2024 20334 CADR GOMARKF # R3 = 0XX.XX SEC.
008304,000090: 32,2025 05472 TC ENDEXT # TERMINATE RETURN
008305,000091: 32,2026 02036 TC AGSVCALC # PROCEED RETURN
008306,000092: 32,2027 44746 CS BIT6 # IS ENTER VIA A V32
008307,000093: 32,2030 60154 AD MPAC
008308,000094: 32,2031 00006 EXTEND
008309,000095: 32,2032 12014 BZF NEWAGS # YES, USE KEYSTROKE TIME FOR NEW AGSK
008310,000096:
008311,000097: 32,2033 00006 EXTEND # NO, NEW AGSK LOADED VIA V25
008312,000098: 32,2034 31051 DCA DSPTEMX # LOADED INTO DSPTEMX BY KEYING
008313,000099: 32,2035 02016 TC REDSPTEM -1 # V25E FOLLOWED BY HRS.,MINS.,SECS.
008314,000100: # DISPLAY THE NEW K
008315,000101:
008316,000102: 32,2036 06042 AGSVCALC TC INTPRET
008317,000103: 32,2037 77614 SET
008318,000104: 32,2040 01076 NODOFLAG # DONT ALLOW V37
008319,000105: 32,2041 77414 SET EXIT
008320,000106: 32,2042 02076 XDSPFLAG
008321,000107:
008322,000108: 32,2043 32172 CAF V06N16
008323,000109: 32,2044 04616 TC BANKCALL
008324,000110: 32,2045 20621 CADR EXDSPRET
008325,000111:
008326,000112: 32,2046 06042 TC INTPRET # EXTRAPOLATE LEM AND CSM STATE VECTORS
008327,000113: 32,2047 77634 RTB # TO THE PRESENT TIME
008328,000114: 32,2050 21574 LOADTIME # LOAD MPAC WITH TIME2,TIME1
008329,000115: 32,2051 34041 STCALL TDEC1 # CALCULATE LEM STATE VECTOR
008330,000116: 32,2052 27056 LEMPREC
008331,000117: 32,2053 77624 CALL # CALL ROUTINE TO CONVERT TO SM COORDS AND
008332,000118: 32,2054 64132 SCALEVEC # PROVIDE PROPER SCALING
008333,000119: 32,2055 16201 STODL AGSBUFF # (LEMPREC AND CSMPREC LEAVE TDEC1 IN TAT)
008334,000120: 32,2056 00015 TAT # TAT = TIME TO WHICH RATT1 AND VATT1 ARE
008335,000121: 32,2057 34041 STCALL TDEC1 # COMPUTED (CSEC SINCE CLOCK START B-28).
008336,000122: 32,2060 27042 CSMPREC # CALCULATE CSM STATE VECTOR FOR SAME TIME
008337,000123: 32,2061 77624 CALL
008338,000124: 32,2062 64132 SCALEVEC
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008340,000126: 32,2063 16207 STODL AGSBUFF +6
008341,000127: 32,2064 00015 TAT
008342,000128: 32,2065 56225 DSU DDV # CALCULATE AND STORE THE TIME
008343,000129: 32,2066 02021 AGSK
008344,000130: 32,2067 24175 TSCALE
008345,000131: 32,2070 02215 STORE AGSBUFF +12D
008346,000132: 32,2071 77776 EXIT
008347,000133:
008348,000134: 32,2072 34753 CAF LAGSLIST
008349,000135: 32,2073 54333 TS DNLSTCOD
008350,000136:
008351,000137: 32,2074 32176 CAF 20SEC # DELAY FOR 20 SEC WHILE THE AGS
008352,000138: 32,2075 04616 TC BANKCALL # DOWNLIST IS TRANSMITTED
008353,000139: 32,2076 01736 CADR DELAYJOB
008354,000140:
008355,000141: 32,2077 31321 CA AGSWORD
008356,000142: 32,2100 54333 TS DNLSTCOD # RETURN TO THE OLD DOWNLIST
008357,000143: 32,2101 34744 CAF IMUSEBIT
008358,000144: 32,2102 70074 MASK FLAGWRD0 # CHECK IMUSE FLAG.
008359,000145: 32,2103 10000 CCS A
008360,000146: 32,2104 02122 TC AGSEND # IMU IS BEING USED - DO NOT ZERO
008361,000147: 32,2105 11301 CKSTALL CCS IMUCADR # CHECK FOR IMU USAGE WHICH AVOIDS THE
008362,000148: 32,2106 12111 TCF +3 # IMUSE BIT: I.E., IMU COMPENSATION.
008363,000149: 32,2107 12115 TCF +6 # FREE. GO AHEAD WITH THE IMU ZERO.
008364,000150: 32,2110 12111 TCF +1
008365,000151: 32,2111 34363 +3 CAF TEN # WAIT .1 SEC AND TRY AGAIN.
008366,000152: 32,2112 04616 TC BANKCALL
008367,000153: 32,2113 01736 CADR DELAYJOB
008368,000154: 32,2114 12105 TCF CKSTALL
008369,000155:
008370,000156: 32,2115 04616 +6 TC BANKCALL # IMU IS NOT IN USE
008371,000157: 32,2116 16705 CADR IMUZERO # SET IMU ZERO DISCRETE FOR 320 MSECS
008372,000158: 32,2117 04616 TC BANKCALL # WAIT 3SEC FOR COUNTERS TO INCREMENT
008373,000159: 32,2120 17707 CADR IMUSTALL
008374,000160: 32,2121 02122 TC AGSEND
008375,000161: 32,2122 05516 AGSEND TC DOWNFLAG # ALLOW V37
008376,000162: 32,2123 00054 ADRES NODOFLAG
008377,000163:
008378,000164: 32,2124 32173 CAF V50N16
008379,000165: 32,2125 04616 TC BANKCALL
008380,000166: 32,2126 20342 CADR GOMARK3
008381,000167: 32,2127 15472 TCF ENDEXT
008382,000168: 32,2130 15472 TCF ENDEXT
008383,000169: 32,2131 05472 TC ENDEXT
008384,000170:
008385,000171: 32,2132 64375 SCALEVEC VLOAD MXV
008386,000172: 32,2133 00025 VATT1
008387,000173: 32,2134 01734 REFSMMAT
008388,000174: 32,2135 72561 VXSC VSL2
008389,000175: 32,2136 24202 VSCALE
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008391,000177: 32,2137 53255 VAD VAD # THIS SECTION ROUNDS THE VECTOR, AND
008392,000178: 32,2140 24204 AGSRND1 # CORRECTS FOR THE FACT THAT THE AGS
008393,000179: 32,2141 24212 AGSRND2 # IS A 2 S COMPLIMENT MACHINE WHILE THE
008394,000180: 32,2142 77634 RTB # LGC IS A 1 S COMPLIMENT MACHINE.
008395,000181: 32,2143 21773 VECSGNAG
008396,000182: 32,2144 24025 STOVL VATT1
008397,000183: 32,2145 00017 RATT1
008398,000184: 32,2146 74321 MXV VXSC
008399,000185: 32,2147 01734 REFSMMAT
008400,000186: 32,2150 24200 RSCALE
008401,000187: 32,2151 53212 VSL8 VAD # AGAIN THIS SECTION ROUNDS. TWO VECTORS
008402,000188: 32,2152 24204 AGSRND1 # ARE ADDED TO DEFEAT ALSIGNAG IN THE
008403,000189: 32,2153 47055 VAD RTB # CASE OF A HIGH-ORDER ZERO COUPLED WITH
008404,000190: 32,2154 24212 AGSRND2 # A LOW ORDER NEGATIVE PART.
008405,000191: 32,2155 21773 VECSGNAG
008406,000192: 32,2156 77750 LXA,1
008407,000193: 32,2157 00024 VATT1
008408,000194: 32,2160 72130 SXA,1 LXA,1
008409,000195: 32,2161 00155 MPAC +1
008410,000196: 32,2162 00026 VATT1 +2
008411,000197: 32,2163 72130 SXA,1 LXA,1
008412,000198: 32,2164 00160 MPAC +4
008413,000199: 32,2165 00030 VATT1 +4
008414,000200: 32,2166 43530 SXA,1 RVQ
008415,000201: 32,2167 00162 MPAC +6
008416,000202:
008417,000203: 32,2170 4753 LAGSLIST = ONE
008418,000204: 32,2170 00216 V01N14 VN 0114
008419,000205: 32,2171 14400 V50N00A VN 5000
008420,000206: 32,2172 6010 V00N25 EQUALS OCT31
008421,000207: 32,2172 01420 V06N16 VN 0616
008422,000208: 32,2173 4242 V00N34 EQUALS 34DEC
008423,000209: 32,2173 14420 V50N16 VN 5016
008424,000210: 32,2174 03100 00000 TSCALE 2DEC 100 B-10 # CSEC TO SEC SCALE FACTOR
008425,000211: 32,2176 03720 20SEC DEC 2000 B-14
008426,000212: 32,2177 15077 05041 RSCALE 2DEC 3.280839 B-3 # METERS TO FEET SCALE FACTOR
008427,000213: 32,2201 24402 25724 VSCALE 2DEC 3.280839 E2 B-9 # METERS/CS TO FEET/SEC SCALE FACTOR
008428,000214: 32,2203 00000 60000 AGSRND1 2OCT 0000060000
008429,000215: 32,2205 00000 60000 2OCT 0000060000
008430,000216: 32,2207 00000 60000 2OCT 0000060000
008431,000217: 32,2211 00000 37777 AGSRND2 2OCT 0000037777
008432,000218: 32,2213 00000 37777 2OCT 0000037777
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008434,000220: 32,2215 00000 37777 2OCT 0000037777
008435,000221:
008436,000222: 32,2217 30,2000 SBANK= LOWSUPER # FOR SUBSEQUENT LOW 2CADRS.
008437,000223:
End of include-file AGS_INITIALIZATION.agc. Parent file is MAIN.agc