Source Code
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These source-code files are part of a reconstructed copy of Luminary 173, the
second (unflown) release of the Apollo 14 Lunar Module (LM) Apollo Guidance
Computer (AGC) software.
The reconstruction began with reconstructed source code for Luminary 178. Changes
between revision 173 and 178 were backed out, as described by Luminary memo 167
(revision 1). 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 173 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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033817,000002: ## Copyright: Public domain.
033818,000003: ## Filename: THROTTLE_CONTROL_ROUTINES.agc
033819,000004: ## Purpose: A section of Luminary revision 173.
033820,000005: ## It is part of the reconstructed source code for the second
033821,000006: ## (unflown) release of the flight software for the Lunar
033822,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 14.
033823,000008: ## The code has been recreated from a reconstructed copy of
033824,000009: ## Luminary 178, as well as Luminary memo 167 (revision 1).
033825,000010: ## It has been adapted such that the resulting bugger words
033826,000011: ## exactly match those specified for Luminary 173 in NASA
033827,000012: ## drawing 2021152N, which gives relatively high confidence
033828,000013: ## that the reconstruction is correct.
033829,000014: ## Reference: pp. 779-783
033830,000015: ## Assembler: yaYUL
033831,000016: ## Contact: Ron Burkey <info@sandroid.org>.
033832,000017: ## Website: www.ibiblio.org/apollo/index.html
033833,000018: ## Mod history: 2019-09-18 MAS Created from Luminary 178.
033834,000019:
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Page 789
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033836,000021: 31,2144 BANK 31
033837,000022:
033838,000023: 31,2000 SETLOC FTHROT
033839,000024:
033840,000025: 31,2000 BANK
033841,000026:
033842,000027: 31,2144 E7,1612 EBANK= PIF
033843,000028:
033844,000029: 31,2144 COUNT* $$/THROT
033845,000030: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
033846,000031: # HERE FC, DESIRED THRUST, AND FP, PRESENT THRUST, UNWEIGHTED, ARE COMPUTED.
033847,000032:
033848,000033: 31,2144 31245 THROTTLE CA ABDELV # COMPUTE PRESENT ACCELERATION IN UNITS OF
033849,000034: 31,2145 00006 EXTEND # 2(-4) M/CS/CS, SAVING SERVICER TROUBLE
033850,000035: 31,2146 72363 MP /AF/CNST
033851,000036: 31,2147 00006 +3 EXTEND
033852,000037: 31,2150 23607 QXCH RTNHOLD
033853,000038: 31,2151 02344 AFDUMP TC MASSMULT
033854,000039: 31,2152 53470 DXCH FP # FP = PRESENT THRUST
033855,000040: 31,2153 00006 EXTEND
033856,000041: 31,2154 31464 DCA /AFC/
033857,000042: 31,2155 02344 TC MASSMULT
033858,000043: 31,2156 00004 INHINT # PREVENT A DOWNRUPT
033859,000044: 31,2157 55615 TS FC # FC = THRUST DESIRED BY GUIDANCE
033860,000045: 31,2160 53466 DXCH FCODD # FCODD = WHAT IT IS GOING TO GET
033861,000046:
033862,000047:
033863,000048: 31,2161 00006 EXTEND
033864,000049: 31,2162 31234 DCA PIPTIME
033865,000050: 31,2163 53753 DXCH GTCTIME # DOWNLINK TIME AGREEMENT
033866,000051: 31,2164 00003 RELINT
033867,000052:
033868,000053: # COMPUTE DESIRED THRUST FOR DISPLAY AS A PERCENTAGE OF 10,500 POUNDS
033869,000054:
033870,000055: 31,2165 32365 CAF 4FMAXNOM # MOVE 4FMAXNOM TO ERASABLE FOR DV BELOW
033871,000056: 31,2166 54002 TS Q
033872,000057: 31,2167 31615 CA FC
033873,000058: 31,2170 72364 MASK OCT17777 # FOR SAFETY
033874,000059: 31,2171 00006 EXTEND
033875,000060: 31,2172 10002 DV Q
033876,000061: 31,2173 00006 EXTEND
033877,000062: 31,2174 75003 MP 4SECS
033878,000063: 31,2175 55750 TS THRDISP # FOR DISPLAY IN N92
033879,000064:
033880,000065: # IF IT HAS BEEN LESS THAN 3 SECONDS SINCE THE LAST THROTTLING, AUGMENT FP USING THE FWEIGHT CALCULATED THEN.
033881,000066:
033882,000067: 31,2176 41617 CS TTHROT # THIS CODING ASSUMES A FLATOUT WITHIN
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Page 790
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033884,000069: 31,2177 60025 AD TIME1 # 80 SECONDS BEFORE FIRST THROTTLE CALL
033885,000070: 31,2200 74733 MASK POSMAX
033886,000071: 31,2201 40000 COM
033887,000072: 31,2202 65002 AD 3SECS
033888,000073: 31,2203 00006 EXTEND
033889,000074: 31,2204 62210 BZMF WHERETO # BRANCH IF (TIME1-TTHROT +1) > 3 SECONDS
033890,000075: 31,2205 00006 EXTEND
033891,000076: 31,2206 31611 DCA FWEIGHT
033892,000077: 31,2207 21470 DAS FP
033893,000078:
033894,000079:
033895,000080: # THIS LOGIC DETERMINES THE THROTTLING IN THE REGION 10% - 94%. THE MANUAL THROTTLE, NOMINALLY SET AT
033896,000081: # MINIMUM BY ASTRONAUT OR MISSION CONTROL PROGRAMS, PROVIDES THE LOWER BOUND. A STOP IN THE THROTTLE HARDWARE
033897,000082: # PROVIDES THE UPPER.
033898,000083:
033899,000084: 31,2210 35014 WHERETO CA EBANK5 # INITIALIZE L*WCR*T AND H*GHCR*T FROM
033900,000085: 31,2211 54003 TS EBANK # PAD LOADED ERASABLES IN W-MATRIX
033901,000086: 31,2212 E5,1472 EBANK= LOWCRIT
033902,000087: 31,2212 00006 EXTEND
033903,000088: 31,2213 31473 DCA LOWCRIT
033904,000089: 31,2214 52131 DXCH L*WCR*T
033905,000090: 31,2215 35016 CA EBANK7
033906,000091: 31,2216 54003 TS EBANK
033907,000092: 31,2217 E7,1612 EBANK= PIF
033908,000093: 31,2217 44755 CS ZERO # INITIALIZE PIFPSET
033909,000094: 31,2220 55606 TS PIFPSET
033910,000095: 31,2221 40131 CS H*GHCR*T
033911,000096: 31,2222 61620 AD FCOLD
033912,000097: 31,2223 00006 EXTEND
033913,000098: 31,2224 62236 BZMF LOWFCOLD # BRANCH IF FCOLD < OR = HIGHCRIT
033914,000099: 31,2225 40130 CS L*WCR*T
033915,000100: 31,2226 61465 AD FCODD
033916,000101: 31,2227 00006 EXTEND
033917,000102: 31,2230 62233 BZMF FCOMPSET # BRANCH IF FC < OR = LOWCRIT
033918,000103: 31,2231 31467 CA FP # SEE NOTE 1
033919,000104: 31,2232 12243 TCF FLATOUT1
033920,000105:
033921,000106: 31,2233 42002 FCOMPSET CS FMAXODD # SEE NOTE 2
033922,000107: 31,2234 61467 AD FP
033923,000108: 31,2235 12245 TCF FLATOUT2
033924,000109:
033925,000110: 31,2236 40131 LOWFCOLD CS H*GHCR*T
033926,000111: 31,2237 61465 AD FCODD
033927,000112: 31,2240 00006 EXTEND
033928,000113: 31,2241 62246 BZMF DOPIF # BRANCH IF FC < OR = HIGHCRIT
033929,000114:
033930,000115: 31,2242 32003 CA FMAXPOS # NO: THROTTLE-UP
033931,000116: 31,2243 53466 FLATOUT1 DXCH FCODD
033932,000117: 31,2244 34737 CA FEXTRA
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Page 791
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033934,000119: 31,2245 55606 FLATOUT2 TS PIFPSET
033935,000120:
033936,000121: # NOTE 1 FC IS SET EQUAL TO FP SO PIF WILL BE ZERO. THIS IS DESIRABLE
033937,000122: # AS THERE IS ACTUALLY NO THROTTLE CHANGE.
033938,000123:
033939,000124: # NOTE 2 HERE, SINCE WE ARE ABOUT TO RETURN TO THE THROTTLEABLE REGION
033940,000125: # (BELOW 55%) THE QUANTITY -(FMAXODD - FP) IS COMPUTED AND PUT
033941,000126: # INTO PIFPSET TO COMPENSATE FOR THE DIFFERENCE BETWEEN THE
033942,000127: # NUMBER OF BITS CORRESPONDING TO FULL THROTTLE (FMAXODD) AND THE
033943,000128: # NUMBER CORRESPONDING TO ACTUAL THRUST (FP). THUS THE TOTAL
033944,000129: # THROTTLE COMMAND PIF = FC - FP -(FMAXODD - FP) = FC - FMAXODD.
033945,000130:
033946,000131: 31,2246 03751 DOPIF TC FASTCHNG
033947,000132: 31,2247 00006 EXTEND
033948,000133: 31,2250 31466 DCA FCODD
033949,000134: 31,2251 55620 TS FCOLD
033950,000135: 31,2252 53613 DXCH PIF
033951,000136: 31,2253 00006 EXTEND
033952,000137: 31,2254 41470 DCS FP
033953,000138: 31,2255 21613 DAS PIF # PIF = FC - FP, NEVER EQUALS +0
033954,000139:
033955,000140:
033956,000141: 31,2256 31612 DOIT CA PIF
033957,000142: 31,2257 61606 AD PIFPSET # ADD IN PIFPSET, WITHOUT CHANGING PIF
033958,000143: 31,2260 55614 TS PSEUDO55
033959,000144: 31,2261 54055 TS THRUST
033960,000145: 31,2262 34750 CAF BIT4
033961,000146: 31,2263 00006 EXTEND
033962,000147: 31,2264 05014 WOR CHAN14
033963,000148: 31,2265 30025 CA TIME1
033964,000149: 31,2266 55617 TS TTHROT
033965,000150:
033966,000151: # SINCE /AF/ IS NOT AN INSTANTANEOUS ACCELERATION, BUT RATHER AN "AVERAGE" OF THE ACCELERATION LEVELS DURING
033967,000152: # THE PRECEEDING PIPA INTERVAL, AND SINCE FP IS COMPUTED DIRECTLY FROM /AF/, FP IN ORDER TO CORRESPOND TO THE
033968,000153: # ACTUAL THRUST LEVEL AT THE END OF THE INTERVAL MUST BE WEIGHTED BY
033969,000154:
033970,000155: # PIF(PPROCESS + TL) PIF /PIF/
033971,000156: # FWEIGHT = ------------------ + -------------
033972,000157: # PGUID 2 PGUID FRATE
033973,000158:
033974,000159: # WHERE PPROCESS IS THE TIME BETWEEN PIPA READING AND THE START OF THROTTLING, PGUID IS THE GUIDANCE PERIOD, AND
033975,000160: # FRATE IS THE THROTTLING RATE (32 UNITS PER CENTISECOND). PGUID IS EITHER 1 OR 2 SECONDS. THE "TL" IN THE
033976,000161: # FIRST TERM REPRESENTS THE ENGINE'S RESPONSE LAG. HERE FWEIGHT IS COMPUTED FOR USE NEXT PASS.
033977,000162:
033978,000163: 31,2267 31762 CA THISTPIP +1 # INITIALIZE FWEIGHT COMP AS IF FOR P66
033979,000164: 31,2270 54130 TS BUF
033980,000165:
033981,000166: 31,2271 41010 CS MODREG # ARE WE IN FACT IN P66?
033982,000167: 31,2272 62454 AD DEC66
033983,000168: 31,2273 00006 EXTEND
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Page 792
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033985,000170: 31,2274 12301 BZF FWCOMP # YES
033986,000171:
033987,000172: 31,2275 31234 CA PIPTIME +1 # NO: INITIALIZE FOR TWO SECOND PERIOD
033988,000173: 31,2276 54130 TS BUF
033989,000174: 31,2277 35003 CAF 4SECS
033990,000175: 31,2300 12302 TCF FWCOMP +1
033991,000176:
033992,000177: 31,2301 35000 FWCOMP CAF 2SECS
033993,000178: 31,2302 54002 +1 TS Q
033994,000179: 31,2303 00006 EXTEND
033995,000180: 31,2304 74746 MP BIT6
033996,000181: 31,2305 22131 LXCH BUF +1
033997,000182: 31,2306 40130 CS BUF # TIME OF LAST PIPA READING.
033998,000183: 31,2307 60025 AD TIME1
033999,000184: 31,2310 62004 AD THROTLAG # COMPENSATE FOR ENGINE RESPONSE LAG
034000,000185: 31,2311 74357 MASK LOW8 # MAKE SURE SMALL AND POSITIVE
034001,000186: 31,2312 22007 ZL
034002,000187: 31,2313 00006 EXTEND
034003,000188: 31,2314 10002 DV Q
034004,000189: 31,2315 00006 EXTEND
034005,000190: 31,2316 71612 MP PIF
034006,000191: 31,2317 60000 DOUBLE
034007,000192: 31,2320 53611 DXCH FWEIGHT
034008,000193: 31,2321 11612 CCS PIF
034009,000194: 31,2322 64753 AD ONE
034010,000195: 31,2323 12325 TCF +2
034011,000196: 31,2324 64753 AD ONE
034012,000197: 31,2325 00006 EXTEND
034013,000198: 31,2326 71612 MP PIF
034014,000199: 31,2327 00006 EXTEND
034015,000200: 31,2330 10131 DV BUF +1
034016,000201: 31,2331 22007 ZL
034017,000202: 31,2332 21611 DAS FWEIGHT
034018,000203:
034019,000204:
034020,000205: 31,2333 01607 THDUMP TC RTNHOLD
034021,000206:
034022,000207:
034023,000208: # FLATOUT THROTTLES UP THE DESCENT ENGINE, AND IS CALLED AS A BASIC SUBROUTINE.
034024,000209:
034025,000210: 31,2334 34737 FLATOUT CAF BIT13 # 4096 PULSES
034026,000211: 31,2335 55606 WHATOUT TS PIFPSET # USE PIFPSET SO FWEIGHT WILL BE ZERO
034027,000212: 31,2336 44755 CS ZERO
034028,000213: 31,2337 55620 TS FCOLD
034029,000214: 31,2340 55612 TS PIF
034030,000215: 31,2341 00006 EXTEND
034031,000216: 31,2342 23607 QXCH RTNHOLD
034032,000217: 31,2343 12256 TCF DOIT
034033,000218:
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Page 793
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034035,000220: # MASSMULT SCALES ACCELERATION, ARRIVING IN A AND L IN UNITS OF 2(-4) M/CS/CS, TO FORCE IN PULSE UNITS.
034036,000221:
034037,000222: 31,2344 00006 MASSMULT EXTEND
034038,000223: 31,2345 22130 QXCH BUF
034039,000224: 31,2346 52155 DXCH MPAC
034040,000225: 31,2347 07106 TC DMP
034041,000226: 31,2350 01243 ADRES MASS
034042,000227: 31,2351 07106 TC DMP # LEAVES PROPERLY SCALED FORCE IM MPAC
034043,000228: 31,2352 02005 ADRES SCALEFAC
034044,000229: 31,2353 07262 TC TPAGREE
034045,000230: 31,2354 30154 CA MPAC
034046,000231: 31,2355 00006 EXTEND
034047,000232: 31,2356 12361 BZF +3
034048,000233: 31,2357 34733 CAF POSMAX
034049,000234: 31,2360 00130 TC BUF
034050,000235: 31,2361 52156 DXCH MPAC +1
034051,000236: 31,2362 00130 TC BUF
034052,000237:
034053,000238:
034054,000239: # CONSTANTS:-
034055,000240:
034056,000241: 31,2363 4737 FEXTRA = BIT13 # FEXT +5.13309020 E+4
034057,000242:
034058,000243: 31,2363 04143 /AF/CNST DEC .13107
034059,000244:
034060,000245: 31,2364 17777 OCT17777 OCT 17777
034061,000246: 31,2365 35074 4FMAXNOM DEC 14908 B-14 # EQUIVALENT TO 10,500 LBS.
034062,000247: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
End of include-file THROTTLE_CONTROL_ROUTINES.agc. Parent file is MAIN.agc