GAP: ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091 17:53 DEC. 19, 1969Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together.
Source Code
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This source code is very close to the Apollo Guidance Computer software for the
Apollo 13 Lunar module. This revision of the Luminary 131 program is from December
of 1969, whereas there was a later revision in January of 1970, and still another
revision in February, which is the code that flew on the mission.
As far as this transcription is concerned, it was originally from a copy made in 1991 of
a printout from the collection of AGC developer Don Eyles for collector David Craig.
It was subsequently scanned by Gary Neff, reprocessed for online
presentation at the now-discontinued History of Recent Science and Technology (HRST) website
of MIT's Dibner Institute (the full-quality scans being discarded in the process),
and finally transcribed by Ron Burkey for the Virtual AGC Project. Although a
high-quality replacement scan for a completely illegible page was later provided by Gary
Neff, the reduced legibility of the reprocessed HRST posting nevertheless caused many
errors to be introduced into the transcription. Accordingly, a second scan of the same physical
printout was made in 2017 for the Virtual AGC Project's collection at the Internet Archive,
and used to correct the transcription errors. All of the scanned materials mentioned,
as well as other Luminary 131 related material, are available online.
Don Eyles apprently made additional hand-written notes in printout between 1991 and 2017,
so the two scans are not identical in that respect. The page-headings in the printout read, in part:GAP: ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091 17:53 DEC. 19, 1969Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together. |
007699,000002: ## Copyright: Public domain.
007700,000003: ## Filename: RCS_FAILURE_MONITOR.agc
007701,000004: ## Purpose: RCS FAILURE MONITOR code for for Luminary 1C, revision 131.
007702,000005: ## It is part of the source code for the Lunar Module's (LM)
007703,000006: ## Apollo Guidance Computer (AGC) for Apollo 13.
007704,000007: ## This file is intended to be a faithful transcription, except
007705,000008: ## that the code format has been changed to conform to the
007706,000009: ## requirements of the yaYUL assembler rather than the
007707,000010: ## original YUL assembler.
007708,000011: ## Reference: pp. 192-194
007709,000012: ## Contact: Ron Burkey <info@sandroid.org>.
007710,000013: ## Website: www.ibiblio.org/apollo/index.html
007711,000014: ## Mod history: 05/05/03 RSB. Began transcribing.
007712,000015: ## 05/14/05 RSB Corrected website references above.
007713,000016: ## 2017-01-06 RSB Page numbers now agree with those on the
007714,000017: ## original harcopy, as opposed to the PDF page
007715,000018: ## numbers in 1701.pdf.
007716,000019: ## 2017-02-16 RSB Proofed comment text using octopus/ProoferComments.
007717,000020: ## 2017-03-14 RSB Comment-text fixes noted in proofing Luminary 116.
007718,000021: ## 2017-08-18 RSB Comment-text bug identified in ZERLINA 56.
007719,000022: ## 2021-05-30 ABS Added missing RCSMON definition to match scans.
007720,000023:
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Page 192 |
007722,000025: # PROGRAM DESCRIPTION
007723,000026:
007724,000027: # AUTHOR: J S MILLER
007725,000028:
007726,000029: # MODIFIED 6 MARCH 1968 BY P S WEISSMAN TO SET UP JOB FOR 1/ACCS WHEN THE MASKS ARE CHANGED.
007727,000030:
007728,000031: # THIS ROUTINE IS ATTACHED TO T4RUPT, AND IS ENTERED EVERY 480 MS. ITS FUNCTION IS TO EXAMINE THE LOW 8 BITS
007729,000032: # OF CHANNEL 32 TO SEE IF ANY ISOLATION-VALVE CLOSURE BITS HAVE APPEARED OR DISAPPEARED (THE CREW IS WARNED OF JET
007730,000033: # FAILURES BY LAMPS LIT BY THE GRUMMAN FAILURE-DETECTION CIRCUITRY; THEY MAY RESPOND BY OPERATING SWITCHES WHICH
007731,000034: # ISOLATE PAIRS OF JETS FROM THE PROPELLANT TANKS AND SET BITS IN CHANNEL 32). IN THE EVENT THAT CHANNEL 32 BITS
007732,000035: # DIFFER FROM 'PVALVEST', THE RECORD OF ACTIONS TAKEN BY THIS ROUTINE, THE APPROPRIATE BITS IN 'CH5MASK' &
007733,000036: # 'CH6MASK', USED BY THE DAP JET-SELECTION LOGIC, ARE UPDATED, AS IS 'PVALVEST'. TO SPEED UP & SHORTEN THE
007734,000037: # ROUTINE, NO MORE THAN ONE CHANGE IS ACCEPTED PER ENTRY. THE HIGHEST-NUMBERED BIT IN CHANNEL 32 WHICH REQUIRES
007735,000038: # ACTION IS THE ONE PROCESSED.
007736,000039:
007737,000040: # THE CODING IN THE FAILURE MONITOR HAS BEEN WRITTEN SO AS TO HAVE ALMOST COMPLETE RESTART PROTECTION. FOR
007738,000041: # EXAMPLE, NO ASSUMPTION IS MADE WHEN SETTING A 'CH5MASK' BIT TO 1 THAT THE PREVIOUS STATE IS 0, ALTHOUGH IT OF
007739,000042: # COURSE SHOULD BE. ONE CASE WHICH MAY BE SEEN TO EVADE PROTECTION IS THE OCCURRENCE OF A RESTART AFTER UPDATING
007740,000043: # ONE OR BOTH DAP MASK-WORDS BUT BEFORE UPDATING 'PVALVEST', COUPLED WITH A CHANGE IN THE VALVE-BIT BACK TO ITS
007741,000044: # FORMER STATE. THE CONSEQUENCE OF THIS IS THAT THE NEXT ENTRY WOULD NOT SEE THE CHANGE INCOMPLETELY INCORP-
007742,000045: # ORATED BY THE LAST PASS (BECAUSE IT WENT AWAY AT JUST THE RIGHT TIME), BUT THE DAP MASK-WORDS WILL BE INCORRECT.
007743,000046: # THIS COMBINATION OF EVENTS SEEMS QUITE REMOTE, BUT NOT IMPOSSIBLE UNLESS THE CREW OPERATES THE SWITCHES AT HALF-
007744,000047: # SECOND INTERVALS OR LONGER. IN ANY EVENT, A DISAGREEMENT BETWEEN REALITY AND THE DAP MASKS WILL BE CURED IF
007745,000048: # THE MISINTERPRETED SWITCH IS REVERSED AND THEN RESTORED TO ITS CORRECT POSITION (SLOWLY).
007746,000049:
007747,000050: # CALLING SEQUENCE:
007748,000051:
007749,000052: # TCF RCSMONIT (IN INTERRUPT MODE, EVERY 480 MS.)
007750,000053:
007751,000054: # EXIT: TCF RCSMONEX (ALL PATHS EXIT VIA SUCH AN INSTRUCTION)
007752,000055:
007753,000056: 06,3164 5270 RCSMONEX EQUALS RESUME
007754,000057:
007755,000058: # ERASABLE INITIALIZATION REQUIRED:
007756,000059:
007757,000060: # VIA FRESH START: PVALVEST = +0 (ALL JETS ENABLED)
007758,000061: # CH5MASK,CH6MASK = +0 (ALL JETS OK)
007759,000062:
007760,000063: # OUTPUT: CH5MASK & CH6MASK UPDATED (1'S WHERE JETS NOT TO BE USED, IN CHANNEL 5 & 6 FORMAT)
007761,000064: # PVALTEST UPDATED (1,S WHEN VALVE CLOSURES HAVE BEEN TRANSLATED INTO CH5MASK & CH6MASK; CHAN 32 FORMAT)
007762,000065: # JOB TO DO 1/ACCS.
007763,000066:
007764,000067: # DEBRIS: A, L, Q AND DEBRIS OF NOVAC.
007765,000068:
007766,000069: # SUBROUTINE CALLED: NOVAC.
007767,000070:
007768,000071: 06,3164 1257 EBANK= CH5MASK
007769,000072:
007770,000073: 23,2000 BANK 23
007771,000074: 06,2000 SETLOC RCSMONT
007772,000075: 06,2000 BANK
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Page 193 |
007774,000077: 06,3164 COUNT* $$/T4RCS
007775,000078:
007776,000079: 06,3164 06,3164 RCSMONIT EQUALS RCSMON
007777,000080:
007778,000081: 06,3164 44755 RCSMON CS ZERO
007779,000082: 06,3165 00006 EXTEND
007780,000083: 06,3166 06032 RXOR CHAN32 # PICK UP + INVERT INVERTED CHANNEL 32.
007781,000084: 06,3167 74357 MASK LOW8 # KEEP JET-FAIL BITS ONLY.
007782,000085: 06,3170 54002 TS Q
007783,000086:
007784,000087: 06,3171 41273 CS PVALVEST # - -
007785,000088: 06,3172 70002 MASK Q # FORM PC + PC.
007786,000089: 06,3173 54001 TS L # (P = PREVIOUS ISOLATION VALVE STATE,
007787,000090: 06,3174 40002 CS Q # C = CURRENT VALVE STATE (CH32)).
007788,000091: 06,3175 71273 MASK PVALVEST
007789,000092: 06,3176 26001 ADS L # RESULT NZ INDICATES ACTION REQUIRED.
007790,000093:
007791,000094: 06,3177 00006 EXTEND
007792,000095: 06,3200 15270 BZF RCSMONEX # QUIT IF NO ACTION REQUIRED.
007793,000096:
007794,000097: 06,3201 00006 EXTEND
007795,000098: 06,3202 74745 MP BIT7 # MOVE BITS 8-1 OF A TO 14-7 OF L.
007796,000099: 06,3203 56001 XCH L # ZERO TO L IN THE PROCESS.
007797,000100:
007798,000101: 06,3204 24001 -3 INCR L
007799,000102: 06,3205 60000 DOUBLE # BOUND TO GET OVERFLOW IN THIS LOOP,
007800,000103: 06,3206 54000 OVSK # SINCE WE ASSURED INITIAL NZ IN A.
007801,000104: 06,3207 13204 TCF -3
007802,000105:
007803,000106: 06,3210 50001 INDEX L
007804,000107: 06,3211 34743 CA BIT8 -1 # SAVE THE RELEVANT BIT (8-1).
007805,000108: 06,3212 54002 TS Q
007806,000109: 06,3213 71273 MASK PVALVEST # LOOK AT PREVIOUS VALVE STATE BIT.
007807,000110: 06,3214 10000 CCS A
007808,000111: 06,3215 13231 TCF VOPENED # THE VALVE HAS JUST BEEN OPENED.
007809,000112:
007810,000113: 06,3216 41257 CS CH5MASK # THE VALVE HAS JUST BEEN CLOSED.
007811,000114: 06,3217 50001 INDEX L
007812,000115: 06,3220 73250 MASK 5FAILTAB
007813,000116: 06,3221 27257 ADS CH5MASK # SET INHIBIT BIT FOR CHANNEL 5 JET.
007814,000117:
007815,000118: 06,3222 41260 CS CH6MASK
007816,000119: 06,3223 50001 INDEX L
007817,000120: 06,3224 73260 MASK 6FAILTAB
007818,000121: 06,3225 27260 ADS CH6MASK # SET INGIBIT BIT FOR CHANNEL 6 JET.
007819,000122:
007820,000123: 06,3226 30002 CA Q
007821,000124: 06,3227 27273 ADS PVALVEST # RECORD ACTION TAKEN.
007822,000125:
007823,000126: 06,3230 13244 TCF 1/ACCFIX # SET UP 1/ACCJOB AND EXIT.
007824,000127:
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Page 194 |
007826,000129: 06,3231 50001 VOPENED INDEX L # A VALVE HAS JUST BEEN OPENED.
007827,000130: 06,3232 43250 CS 5FAILTAB
007828,000131: 06,3233 71257 MASK CH5MASK
007829,000132: 06,3234 55257 TS CH5MASK # REMOVE INHIBIT BIT FOR CHANNEL 5 JET.
007830,000133:
007831,000134: 06,3235 50001 INDEX L
007832,000135: 06,3236 43260 CS 6FAILTAB
007833,000136: 06,3237 71260 MASK CH6MASK
007834,000137: 06,3240 55260 TS CH6MASK # REMOVE INHIBIT BIT FOR CHANNEL 6 JET.
007835,000138:
007836,000139: 06,3241 40002 CS Q
007837,000140: 06,3242 71273 MASK PVALVEST
007838,000141: 06,3243 55273 TS PVALVEST # RECORD ACTION TAKEN.
007839,000142:
007840,000143: 06,3244 37720 1/ACCFIX CAF PRIO27 # SET UP 1/ACCS SO THAT THE SWITCH CURVES
007841,000144: 06,3245 05072 TC NOVAC # FOR TJETLAW CAN BE MODIFIED IF CH5MASK
007842,000145: 06,3246 E6,1536 EBANK= AOSQ # HAS BEEN ALTERED.
007843,000146: 06,3246 03652 42106 2CADR 1/ACCJOB
007844,000147:
007845,000148: 06,3250 15270 TCF RCSMONEX # EXIT.
007846,000149:
007847,000150: 06,3251 5FAILTAB EQUALS -1 # CH 5 JET BIT CORRESPONDING TO CH 32 BIT:
007848,000151: 06,3251 00040 OCT 00040 # 8
007849,000152: 06,3252 00020 OCT 00020 # 7
007850,000153: 06,3253 00100 OCT 00100 # 6
007851,000154: 06,3254 00200 OCT 00200 # 5
007852,000155: 06,3255 00010 OCT 00010 # 4
007853,000156: 06,3256 00001 OCT 00001 # 3
007854,000157: 06,3257 00004 OCT 00004 # 2
007855,000158: 06,3260 00002 OCT 00002 # 1
007856,000159:
007857,000160: 06,3261 6FAILTAB EQUALS -1 # CH 6 JET BIT CORRESPONDING TO CH 32 BIT:
007858,000161: 06,3261 00010 OCT 00010 # 8
007859,000162: 06,3262 00020 OCT 00020 # 7
007860,000163: 06,3263 00004 OCT 00004 # 6
007861,000164: 06,3264 00200 OCT 00200 # 5
007862,000165: 06,3265 00001 OCT 00001 # 4
007863,000166: 06,3266 00002 OCT 00002 # 3
007864,000167: 06,3267 00040 OCT 00040 # 2
007865,000168: 06,3270 00100 OCT 00100 # 1
007866,000169:
007867,000170:
End of include-file RCS_FAILURE_MONITOR.agc. Parent file is MAIN.agc