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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007621,000002: ## Copyright: Public domain.
007622,000003: ## Filename: RCS_FAILURE_MONITOR.agc
007623,000004: ## Purpose: A section of LM131 revision 1.
007624,000005: ## It is part of the reconstructed source code for the final
007625,000006: ## release of the flight software for the Lunar Module's (LM)
007626,000007: ## Apollo Guidance Computer (AGC) for Apollo 13. The code has
007627,000008: ## been reconstructed from a listing of Luminary 131 and a dump
007628,000009: ## of a core rope memory module B5, part number 2010802-171,
007629,000010: ## which is the only module different between LM131 revision 1
007630,000011: ## and Luminary 131. The executable generated from this source
007631,000012: ## has been verified against the module dump, so while the names,
007632,000013: ## comments, and ordering may not be exactly correct, the
007633,000014: ## resulting binary is.
007634,000015: ## Reference: pp. 192-194
007635,000016: ## Assembler: yaYUL
007636,000017: ## Contact: Ron Burkey <info@sandroid.org>.
007637,000018: ## Website: www.ibiblio.org/apollo/index.html
007638,000019: ## Mod history: 2022-10-28 MAS Created from Luminary 131.
007639,000020:
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Page 192
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007641,000022: # PROGRAM DESCRIPTION
007642,000023:
007643,000024: # AUTHOR: J S MILLER
007644,000025:
007645,000026: # MODIFIED 6 MARCH 1968 BY P S WEISSMAN TO SET UP JOB FOR 1/ACCS WHEN THE MASKS ARE CHANGED.
007646,000027:
007647,000028: # THIS ROUTINE IS ATTACHED TO T4RUPT, AND IS ENTERED EVERY 480 MS. ITS FUNCTION IS TO EXAMINE THE LOW 8 BITS
007648,000029: # OF CHANNEL 32 TO SEE IF ANY ISOLATION-VALVE CLOSURE BITS HAVE APPEARED OR DISAPPEARED (THE CREW IS WARNED OF JET
007649,000030: # FAILURES BY LAMPS LIT BY THE GRUMMAN FAILURE-DETECTION CIRCUITRY; THEY MAY RESPOND BY OPERATING SWITCHES WHICH
007650,000031: # ISOLATE PAIRS OF JETS FROM THE PROPELLANT TANKS AND SET BITS IN CHANNEL 32). IN THE EVENT THAT CHANNEL 32 BITS
007651,000032: # DIFFER FROM 'PVALVEST', THE RECORD OF ACTIONS TAKEN BY THIS ROUTINE, THE APPROPRIATE BITS IN 'CH5MASK' &
007652,000033: # 'CH6MASK', USED BY THE DAP JET-SELECTION LOGIC, ARE UPDATED, AS IS 'PVALVEST'. TO SPEED UP & SHORTEN THE
007653,000034: # ROUTINE, NO MORE THAN ONE CHANGE IS ACCEPTED PER ENTRY. THE HIGHEST-NUMBERED BIT IN CHANNEL 32 WHICH REQUIRES
007654,000035: # ACTION IS THE ONE PROCESSED.
007655,000036:
007656,000037: # THE CODING IN THE FAILURE MONITOR HAS BEEN WRITTEN SO AS TO HAVE ALMOST COMPLETE RESTART PROTECTION. FOR
007657,000038: # EXAMPLE, NO ASSUMPTION IS MADE WHEN SETTING A 'CH5MASK' BIT TO 1 THAT THE PREVIOUS STATE IS 0, ALTHOUGH IT OF
007658,000039: # COURSE SHOULD BE. ONE CASE WHICH MAY BE SEEN TO EVADE PROTECTION IS THE OCCURRENCE OF A RESTART AFTER UPDATING
007659,000040: # ONE OR BOTH DAP MASK-WORDS BUT BEFORE UPDATING 'PVALVEST', COUPLED WITH A CHANGE IN THE VALVE-BIT BACK TO ITS
007660,000041: # FORMER STATE. THE CONSEQUENCE OF THIS IS THAT THE NEXT ENTRY WOULD NOT SEE THE CHANGE INCOMPLETELY INCORP-
007661,000042: # ORATED BY THE LAST PASS (BECAUSE IT WENT AWAY AT JUST THE RIGHT TIME), BUT THE DAP MASK-WORDS WILL BE INCORRECT.
007662,000043: # THIS COMBINATION OF EVENTS SEEMS QUITE REMOTE, BUT NOT IMPOSSIBLE UNLESS THE CREW OPERATES THE SWITCHES AT HALF-
007663,000044: # SECOND INTERVALS OR LONGER. IN ANY EVENT, A DISAGREEMENT BETWEEN REALITY AND THE DAP MASKS WILL BE CURED IF
007664,000045: # THE MISINTERPRETED SWITCH IS REVERSED AND THEN RESTORED TO ITS CORRECT POSITION (SLOWLY).
007665,000046:
007666,000047: # CALLING SEQUENCE:
007667,000048:
007668,000049: # TCF RCSMONIT (IN INTERRUPT MODE, EVERY 480 MS.)
007669,000050:
007670,000051: # EXIT: TCF RCSMONEX (ALL PATHS EXIT VIA SUCH AN INSTRUCTION)
007671,000052:
007672,000053: 06,3164 5270 RCSMONEX EQUALS RESUME
007673,000054:
007674,000055: # ERASABLE INITIALIZATION REQUIRED:
007675,000056:
007676,000057: # VIA FRESH START: PVALVEST = +0 (ALL JETS ENABLED)
007677,000058: # CH5MASK,CH6MASK = +0 (ALL JETS OK)
007678,000059:
007679,000060: # OUTPUT: CH5MASK & CH6MASK UPDATED (1'S WHERE JETS NOT TO BE USED, IN CHANNEL 5 & 6 FORMAT)
007680,000061: # PVALTEST UPDATED (1,S WHEN VALVE CLOSURES HAVE BEEN TRANSLATED INTO CH5MASK & CH6MASK; CHAN 32 FORMAT)
007681,000062: # JOB TO DO 1/ACCS.
007682,000063:
007683,000064: # DEBRIS: A, L, Q AND DEBRIS OF NOVAC.
007684,000065:
007685,000066: # SUBROUTINE CALLED: NOVAC.
007686,000067:
007687,000068: 06,3164 1257 EBANK= CH5MASK
007688,000069:
007689,000070: 23,2000 BANK 23
007690,000071: 06,2000 SETLOC RCSMONT
007691,000072: 06,2000 BANK
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Page 193
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007693,000074: 06,3164 COUNT* $$/T4RCS
007694,000075:
007695,000076: 06,3164 06,3164 RCSMONIT EQUALS RCSMON
007696,000077:
007697,000078: 06,3164 44755 RCSMON CS ZERO
007698,000079: 06,3165 00006 EXTEND
007699,000080: 06,3166 06032 RXOR CHAN32 # PICK UP + INVERT INVERTED CHANNEL 32.
007700,000081: 06,3167 74357 MASK LOW8 # KEEP JET-FAIL BITS ONLY.
007701,000082: 06,3170 54002 TS Q
007702,000083:
007703,000084: 06,3171 41273 CS PVALVEST # - -
007704,000085: 06,3172 70002 MASK Q # FORM PC + PC.
007705,000086: 06,3173 54001 TS L # (P = PREVIOUS ISOLATION VALVE STATE,
007706,000087: 06,3174 40002 CS Q # C = CURRENT VALVE STATE (CH32)).
007707,000088: 06,3175 71273 MASK PVALVEST
007708,000089: 06,3176 26001 ADS L # RESULT NZ INDICATES ACTION REQUIRED.
007709,000090:
007710,000091: 06,3177 00006 EXTEND
007711,000092: 06,3200 15270 BZF RCSMONEX # QUIT IF NO ACTION REQUIRED.
007712,000093:
007713,000094: 06,3201 00006 EXTEND
007714,000095: 06,3202 74745 MP BIT7 # MOVE BITS 8-1 OF A TO 14-7 OF L.
007715,000096: 06,3203 56001 XCH L # ZERO TO L IN THE PROCESS.
007716,000097:
007717,000098: 06,3204 24001 -3 INCR L
007718,000099: 06,3205 60000 DOUBLE # BOUND TO GET OVERFLOW IN THIS LOOP,
007719,000100: 06,3206 54000 OVSK # SINCE WE ASSURED INITIAL NZ IN A.
007720,000101: 06,3207 13204 TCF -3
007721,000102:
007722,000103: 06,3210 50001 INDEX L
007723,000104: 06,3211 34743 CA BIT8 -1 # SAVE THE RELEVANT BIT (8-1).
007724,000105: 06,3212 54002 TS Q
007725,000106: 06,3213 71273 MASK PVALVEST # LOOK AT PREVIOUS VALVE STATE BIT.
007726,000107: 06,3214 10000 CCS A
007727,000108: 06,3215 13231 TCF VOPENED # THE VALVE HAS JUST BEEN OPENED.
007728,000109:
007729,000110: 06,3216 41257 CS CH5MASK # THE VALVE HAS JUST BEEN CLOSED.
007730,000111: 06,3217 50001 INDEX L
007731,000112: 06,3220 73250 MASK 5FAILTAB
007732,000113: 06,3221 27257 ADS CH5MASK # SET INHIBIT BIT FOR CHANNEL 5 JET.
007733,000114:
007734,000115: 06,3222 41260 CS CH6MASK
007735,000116: 06,3223 50001 INDEX L
007736,000117: 06,3224 73260 MASK 6FAILTAB
007737,000118: 06,3225 27260 ADS CH6MASK # SET INGIBIT BIT FOR CHANNEL 6 JET.
007738,000119:
007739,000120: 06,3226 30002 CA Q
007740,000121: 06,3227 27273 ADS PVALVEST # RECORD ACTION TAKEN.
007741,000122:
007742,000123: 06,3230 13244 TCF 1/ACCFIX # SET UP 1/ACCJOB AND EXIT.
007743,000124:
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Page 194
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007745,000126: 06,3231 50001 VOPENED INDEX L # A VALVE HAS JUST BEEN OPENED.
007746,000127: 06,3232 43250 CS 5FAILTAB
007747,000128: 06,3233 71257 MASK CH5MASK
007748,000129: 06,3234 55257 TS CH5MASK # REMOVE INHIBIT BIT FOR CHANNEL 5 JET.
007749,000130:
007750,000131: 06,3235 50001 INDEX L
007751,000132: 06,3236 43260 CS 6FAILTAB
007752,000133: 06,3237 71260 MASK CH6MASK
007753,000134: 06,3240 55260 TS CH6MASK # REMOVE INHIBIT BIT FOR CHANNEL 6 JET.
007754,000135:
007755,000136: 06,3241 40002 CS Q
007756,000137: 06,3242 71273 MASK PVALVEST
007757,000138: 06,3243 55273 TS PVALVEST # RECORD ACTION TAKEN.
007758,000139:
007759,000140: 06,3244 37720 1/ACCFIX CAF PRIO27 # SET UP 1/ACCS SO THAT THE SWITCH CURVES
007760,000141: 06,3245 05072 TC NOVAC # FOR TJETLAW CAN BE MODIFIED IF CH5MASK
007761,000142: 06,3246 E6,1536 EBANK= AOSQ # HAS BEEN ALTERED.
007762,000143: 06,3246 03652 42106 2CADR 1/ACCJOB
007763,000144:
007764,000145: 06,3250 15270 TCF RCSMONEX # EXIT.
007765,000146:
007766,000147: 06,3251 5FAILTAB EQUALS -1 # CH 5 JET BIT CORRESPONDING TO CH 32 BIT:
007767,000148: 06,3251 00040 OCT 00040 # 8
007768,000149: 06,3252 00020 OCT 00020 # 7
007769,000150: 06,3253 00100 OCT 00100 # 6
007770,000151: 06,3254 00200 OCT 00200 # 5
007771,000152: 06,3255 00010 OCT 00010 # 4
007772,000153: 06,3256 00001 OCT 00001 # 3
007773,000154: 06,3257 00004 OCT 00004 # 2
007774,000155: 06,3260 00002 OCT 00002 # 1
007775,000156:
007776,000157: 06,3261 6FAILTAB EQUALS -1 # CH 6 JET BIT CORRESPONDING TO CH 32 BIT:
007777,000158: 06,3261 00010 OCT 00010 # 8
007778,000159: 06,3262 00020 OCT 00020 # 7
007779,000160: 06,3263 00004 OCT 00004 # 6
007780,000161: 06,3264 00200 OCT 00200 # 5
007781,000162: 06,3265 00001 OCT 00001 # 4
007782,000163: 06,3266 00002 OCT 00002 # 3
007783,000164: 06,3267 00040 OCT 00040 # 2
007784,000165: 06,3270 00100 OCT 00100 # 1
007785,000166:
007786,000167:
End of include-file RCS_FAILURE_MONITOR.agc. Parent file is MAIN.agc