Source Code
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These source-code files are part of a reconstructed copy of Luminary 178, the
final release of the Apollo 14 Lunar Module (LM) Apollo Guidance Computer
(AGC) software.
The reconstruction began with source code of Zerlina 56, Luminary 210, and
Luminary 131, previously transcribed from digitized copies of those programs.
The code was created by combining the three, using Zerlina 56 as a base, since
it was based off of Luminary 183. The differences between the three were
carefully merged using the Luminary memos as a guide, with all changes made
after Luminary 178 being backed out. The reconstruction was verified by matching
memory-bank checksums to those listed in drawing 2021152N. Note that page numbers
in the reconstructed code match those for the baseline log section mentioned in
each file's changelog; the page numbers for a real Luminary 178 listing would
be different.
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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033869,000002: ## Copyright: Public domain.
033870,000003: ## Filename: THROTTLE_CONTROL_ROUTINES.agc
033871,000004: ## Purpose: A section of Luminary revision 178.
033872,000005: ## It is part of the reconstructed source code for the final
033873,000006: ## release of the flight software for the Lunar Module's
033874,000007: ## (LM) Apollo Guidance Computer (AGC) for Apollo 14. The
033875,000008: ## code has been recreated from copies of Zerlina 56, Luminary
033876,000009: ## 210, and Luminary 131, as well as many Luminary memos.
033877,000010: ## It has been adapted such that the resulting bugger words
033878,000011: ## exactly match those specified for Luminary 178 in NASA
033879,000012: ## drawing 2021152N, which gives relatively high confidence
033880,000013: ## that the reconstruction is correct.
033881,000014: ## Reference: pp. 779-783
033882,000015: ## Assembler: yaYUL
033883,000016: ## Contact: Ron Burkey <info@sandroid.org>.
033884,000017: ## Website: www.ibiblio.org/apollo/index.html
033885,000018: ## Mod history: 2019-08-14 MAS Created from Zerlina 56.
033886,000019: ## 2019-09-08 MAS Re-based on Luminary 210, since Don entirely
033887,000020: ## rewrote this section in Zerlina. Undid a
033888,000021: ## couple of small changes made after Luminary
033889,000022: ## 178; namely a DXCH->XCH and a DOUBLE->DDOUBL.
033890,000023:
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Page 789
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033892,000025: 31,2144 BANK 31
033893,000026:
033894,000027: 31,2000 SETLOC FTHROT
033895,000028:
033896,000029: 31,2000 BANK
033897,000030:
033898,000031: 31,2144 E7,1612 EBANK= PIF
033899,000032:
033900,000033: 31,2144 COUNT* $$/THROT
033901,000034: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
033902,000035: # HERE FC, DESIRED THRUST, AND FP, PRESENT THRUST, UNWEIGHTED, ARE COMPUTED.
033903,000036:
033904,000037: 31,2144 31245 THROTTLE CA ABDELV # COMPUTE PRESENT ACCELERATION IN UNITS OF
033905,000038: 31,2145 00006 EXTEND # 2(-4) M/CS/CS, SAVING SERVICER TROUBLE
033906,000039: 31,2146 72363 MP /AF/CNST
033907,000040: 31,2147 00006 +3 EXTEND
033908,000041: 31,2150 23607 QXCH RTNHOLD
033909,000042: 31,2151 02344 AFDUMP TC MASSMULT
033910,000043: 31,2152 53470 DXCH FP # FP = PRESENT THRUST
033911,000044: 31,2153 00006 EXTEND
033912,000045: 31,2154 31464 DCA /AFC/
033913,000046: 31,2155 02344 TC MASSMULT
033914,000047: 31,2156 00004 INHINT # PREVENT A DOWNRUPT
033915,000048: 31,2157 55615 TS FC # FC = THRUST DESIRED BY GUIDANCE
033916,000049: 31,2160 53466 DXCH FCODD # FCODD = WHAT IT IS GOING TO GET
033917,000050:
033918,000051:
033919,000052: 31,2161 00006 EXTEND
033920,000053: 31,2162 31234 DCA PIPTIME
033921,000054: 31,2163 53753 DXCH GTCTIME # DOWNLINK TIME AGREEMENT
033922,000055: 31,2164 00003 RELINT
033923,000056:
033924,000057: # COMPUTE DESIRED THRUST FOR DISPLAY AS A PERCENTAGE OF 10,500 POUNDS
033925,000058:
033926,000059: 31,2165 32365 CAF 4FMAXNOM # MOVE 4FMAXNOM TO ERASABLE FOR DV BELOW
033927,000060: 31,2166 54002 TS Q
033928,000061: 31,2167 31615 CA FC
033929,000062: 31,2170 72364 MASK OCT17777 # FOR SAFETY
033930,000063: 31,2171 00006 EXTEND
033931,000064: 31,2172 10002 DV Q
033932,000065: 31,2173 00006 EXTEND
033933,000066: 31,2174 75003 MP 4SECS
033934,000067: 31,2175 55750 TS THRDISP # FOR DISPLAY IN N92
033935,000068:
033936,000069: # IF IT HAS BEEN LESS THAN 3 SECONDS SINCE THE LAST THROTTLING, AUGMENT FP USING THE FWEIGHT CALCULATED THEN.
033937,000070:
033938,000071: 31,2176 41617 CS TTHROT # THIS CODING ASSUMES A FLATOUT WITHIN
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Page 790
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033940,000073: 31,2177 60025 AD TIME1 # 80 SECONDS BEFORE FIRST THROTTLE CALL
033941,000074: 31,2200 74733 MASK POSMAX
033942,000075: 31,2201 40000 COM
033943,000076: 31,2202 65002 AD 3SECS
033944,000077: 31,2203 00006 EXTEND
033945,000078: 31,2204 62210 BZMF WHERETO # BRANCH IF (TIME1-TTHROT +1) > 3 SECONDS
033946,000079: 31,2205 00006 EXTEND
033947,000080: 31,2206 31611 DCA FWEIGHT
033948,000081: 31,2207 21470 DAS FP
033949,000082:
033950,000083:
033951,000084: # THIS LOGIC DETERMINES THE THROTTLING IN THE REGION 10% - 94%. THE MANUAL THROTTLE, NOMINALLY SET AT
033952,000085: # MINIMUM BY ASTRONAUT OR MISSION CONTROL PROGRAMS, PROVIDES THE LOWER BOUND. A STOP IN THE THROTTLE HARDWARE
033953,000086: # PROVIDES THE UPPER.
033954,000087:
033955,000088: 31,2210 35014 WHERETO CA EBANK5 # INITIALIZE L*WCR*T AND H*GHCR*T FROM
033956,000089: 31,2211 54003 TS EBANK # PAD LOADED ERASABLES IN W-MATRIX
033957,000090: 31,2212 E5,1472 EBANK= LOWCRIT
033958,000091: 31,2212 00006 EXTEND
033959,000092: 31,2213 31473 DCA LOWCRIT
033960,000093: 31,2214 52131 DXCH L*WCR*T
033961,000094: 31,2215 35016 CA EBANK7
033962,000095: 31,2216 54003 TS EBANK
033963,000096: 31,2217 E7,1612 EBANK= PIF
033964,000097: 31,2217 44755 CS ZERO # INITIALIZE PIFPSET
033965,000098: 31,2220 55606 TS PIFPSET
033966,000099: 31,2221 40131 CS H*GHCR*T
033967,000100: 31,2222 61620 AD FCOLD
033968,000101: 31,2223 00006 EXTEND
033969,000102: 31,2224 62236 BZMF LOWFCOLD # BRANCH IF FCOLD < OR = HIGHCRIT
033970,000103: 31,2225 40130 CS L*WCR*T
033971,000104: 31,2226 61465 AD FCODD
033972,000105: 31,2227 00006 EXTEND
033973,000106: 31,2230 62233 BZMF FCOMPSET # BRANCH IF FC < OR = LOWCRIT
033974,000107: 31,2231 31467 CA FP # SEE NOTE 1
033975,000108: 31,2232 12243 TCF FLATOUT1
033976,000109:
033977,000110: 31,2233 42002 FCOMPSET CS FMAXODD # SEE NOTE 2
033978,000111: 31,2234 61467 AD FP
033979,000112: 31,2235 12245 TCF FLATOUT2
033980,000113:
033981,000114: 31,2236 40131 LOWFCOLD CS H*GHCR*T
033982,000115: 31,2237 61465 AD FCODD
033983,000116: 31,2240 00006 EXTEND
033984,000117: 31,2241 62246 BZMF DOPIF # BRANCH IF FC < OR = HIGHCRIT
033985,000118:
033986,000119: 31,2242 32003 CA FMAXPOS # NO: THROTTLE-UP
033987,000120: 31,2243 53466 FLATOUT1 DXCH FCODD
033988,000121: 31,2244 34737 CA FEXTRA
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Page 791
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033990,000123: 31,2245 55606 FLATOUT2 TS PIFPSET
033991,000124:
033992,000125: # NOTE 1 FC IS SET EQUAL TO FP SO PIF WILL BE ZERO. THIS IS DESIRABLE
033993,000126: # AS THERE IS ACTUALLY NO THROTTLE CHANGE.
033994,000127:
033995,000128: # NOTE 2 HERE, SINCE WE ARE ABOUT TO RETURN TO THE THROTTLEABLE REGION
033996,000129: # (BELOW 55%) THE QUANTITY -(FMAXODD - FP) IS COMPUTED AND PUT
033997,000130: # INTO PIFPSET TO COMPENSATE FOR THE DIFFERENCE BETWEEN THE
033998,000131: # NUMBER OF BITS CORRESPONDING TO FULL THROTTLE (FMAXODD) AND THE
033999,000132: # NUMBER CORRESPONDING TO ACTUAL THRUST (FP). THUS THE TOTAL
034000,000133: # THROTTLE COMMAND PIF = FC - FP -(FMAXODD - FP) = FC - FMAXODD.
034001,000134:
034002,000135: 31,2246 03741 DOPIF TC FASTCHNG
034003,000136: 31,2247 00006 EXTEND
034004,000137: 31,2250 31466 DCA FCODD
034005,000138: 31,2251 55620 TS FCOLD
034006,000139: 31,2252 53613 DXCH PIF
034007,000140: 31,2253 00006 EXTEND
034008,000141: 31,2254 41470 DCS FP
034009,000142: 31,2255 21613 DAS PIF # PIF = FC - FP, NEVER EQUALS +0
034010,000143:
034011,000144:
034012,000145: 31,2256 31612 DOIT CA PIF
034013,000146: 31,2257 61606 AD PIFPSET # ADD IN PIFPSET, WITHOUT CHANGING PIF
034014,000147: 31,2260 55614 TS PSEUDO55
034015,000148: 31,2261 54055 TS THRUST
034016,000149: 31,2262 34750 CAF BIT4
034017,000150: 31,2263 00006 EXTEND
034018,000151: 31,2264 05014 WOR CHAN14
034019,000152: 31,2265 30025 CA TIME1
034020,000153: 31,2266 55617 TS TTHROT
034021,000154:
034022,000155: # SINCE /AF/ IS NOT AN INSTANTANEOUS ACCELERATION, BUT RATHER AN "AVERAGE" OF THE ACCELERATION LEVELS DURING
034023,000156: # THE PRECEEDING PIPA INTERVAL, AND SINCE FP IS COMPUTED DIRECTLY FROM /AF/, FP IN ORDER TO CORRESPOND TO THE
034024,000157: # ACTUAL THRUST LEVEL AT THE END OF THE INTERVAL MUST BE WEIGHTED BY
034025,000158:
034026,000159: # PIF(PPROCESS + TL) PIF /PIF/
034027,000160: # FWEIGHT = ------------------ + -------------
034028,000161: # PGUID 2 PGUID FRATE
034029,000162:
034030,000163: # WHERE PPROCESS IS THE TIME BETWEEN PIPA READING AND THE START OF THROTTLING, PGUID IS THE GUIDANCE PERIOD, AND
034031,000164: # FRATE IS THE THROTTLING RATE (32 UNITS PER CENTISECOND). PGUID IS EITHER 1 OR 2 SECONDS. THE "TL" IN THE
034032,000165: # FIRST TERM REPRESENTS THE ENGINE'S RESPONSE LAG. HERE FWEIGHT IS COMPUTED FOR USE NEXT PASS.
034033,000166:
034034,000167: 31,2267 31762 CA THISTPIP +1 # INITIALIZE FWEIGHT COMP AS IF FOR P66
034035,000168: 31,2270 54130 TS BUF
034036,000169:
034037,000170: 31,2271 41010 CS MODREG # ARE WE IN FACT IN P66?
034038,000171: 31,2272 62454 AD DEC66
034039,000172: 31,2273 00006 EXTEND
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Page 792
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034041,000174: 31,2274 12301 BZF FWCOMP # YES
034042,000175:
034043,000176: 31,2275 31234 CA PIPTIME +1 # NO: INITIALIZE FOR TWO SECOND PERIOD
034044,000177: 31,2276 54130 TS BUF
034045,000178: 31,2277 35003 CAF 4SECS
034046,000179: 31,2300 12302 TCF FWCOMP +1
034047,000180:
034048,000181: 31,2301 35000 FWCOMP CAF 2SECS
034049,000182: 31,2302 54002 +1 TS Q
034050,000183: 31,2303 00006 EXTEND
034051,000184: 31,2304 74746 MP BIT6
034052,000185: 31,2305 22131 LXCH BUF +1
034053,000186: 31,2306 40130 CS BUF # TIME OF LAST PIPA READING.
034054,000187: 31,2307 60025 AD TIME1
034055,000188: 31,2310 62004 AD THROTLAG # COMPENSATE FOR ENGINE RESPONSE LAG
034056,000189: 31,2311 74357 MASK LOW8 # MAKE SURE SMALL AND POSITIVE
034057,000190: 31,2312 22007 ZL
034058,000191: 31,2313 00006 EXTEND
034059,000192: 31,2314 10002 DV Q
034060,000193: 31,2315 00006 EXTEND
034061,000194: 31,2316 71612 MP PIF
034062,000195: 31,2317 60000 DOUBLE
034063,000196: 31,2320 53611 DXCH FWEIGHT
034064,000197: 31,2321 11612 CCS PIF
034065,000198: 31,2322 64753 AD ONE
034066,000199: 31,2323 12325 TCF +2
034067,000200: 31,2324 64753 AD ONE
034068,000201: 31,2325 00006 EXTEND
034069,000202: 31,2326 71612 MP PIF
034070,000203: 31,2327 00006 EXTEND
034071,000204: 31,2330 10131 DV BUF +1
034072,000205: 31,2331 22007 ZL
034073,000206: 31,2332 21611 DAS FWEIGHT
034074,000207:
034075,000208:
034076,000209: 31,2333 01607 THDUMP TC RTNHOLD
034077,000210:
034078,000211:
034079,000212: # FLATOUT THROTTLES UP THE DESCENT ENGINE, AND IS CALLED AS A BASIC SUBROUTINE.
034080,000213:
034081,000214: 31,2334 34737 FLATOUT CAF BIT13 # 4096 PULSES
034082,000215: 31,2335 55606 WHATOUT TS PIFPSET # USE PIFPSET SO FWEIGHT WILL BE ZERO
034083,000216: 31,2336 44755 CS ZERO
034084,000217: 31,2337 55620 TS FCOLD
034085,000218: 31,2340 55612 TS PIF
034086,000219: 31,2341 00006 EXTEND
034087,000220: 31,2342 23607 QXCH RTNHOLD
034088,000221: 31,2343 12256 TCF DOIT
034089,000222:
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Page 793
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034091,000224: # MASSMULT SCALES ACCELERATION, ARRIVING IN A AND L IN UNITS OF 2(-4) M/CS/CS, TO FORCE IN PULSE UNITS.
034092,000225:
034093,000226: 31,2344 00006 MASSMULT EXTEND
034094,000227: 31,2345 22130 QXCH BUF
034095,000228: 31,2346 52155 DXCH MPAC
034096,000229: 31,2347 07106 TC DMP
034097,000230: 31,2350 01243 ADRES MASS
034098,000231: 31,2351 07106 TC DMP # LEAVES PROPERLY SCALED FORCE IM MPAC
034099,000232: 31,2352 02005 ADRES SCALEFAC
034100,000233: 31,2353 07262 TC TPAGREE
034101,000234: 31,2354 30154 CA MPAC
034102,000235: 31,2355 00006 EXTEND
034103,000236: 31,2356 12361 BZF +3
034104,000237: 31,2357 34733 CAF POSMAX
034105,000238: 31,2360 00130 TC BUF
034106,000239: 31,2361 52156 DXCH MPAC +1
034107,000240: 31,2362 00130 TC BUF
034108,000241:
034109,000242:
034110,000243: # CONSTANTS:-
034111,000244:
034112,000245: 31,2363 4737 FEXTRA = BIT13 # FEXT +5.13309020 E+4
034113,000246:
034114,000247: 31,2363 04143 /AF/CNST DEC .13107
034115,000248:
034116,000249: 31,2364 17777 OCT17777 OCT 17777
034117,000250: 31,2365 35074 4FMAXNOM DEC 14908 B-14 # EQUIVALENT TO 10,500 LBS.
034118,000251: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
End of include-file THROTTLE_CONTROL_ROUTINES.agc. Parent file is MAIN.agc