Source Code
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These source-code files are part of a reconstructed copy of Luminary 163, the
first (unflown) release of the Apollo 14 Lunar Module (LM) Apollo Guidance
Computer (AGC) software.
The reconstruction began with reconstructed source code for Luminary 173. Changes
between revision 163 and 173 were backed out, as described by Luminary memos 157
and 158. 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 163 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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033797,000002: ## Copyright: Public domain.
033798,000003: ## Filename: THROTTLE_CONTROL_ROUTINES.agc
033799,000004: ## Purpose: A section of Luminary revision 163.
033800,000005: ## It is part of the reconstructed source code for the first
033801,000006: ## (unflown) release of the flight software for the Lunar
033802,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 14.
033803,000008: ## The code has been recreated from a reconstructed copy of
033804,000009: ## Luminary 173, as well as Luminary memos 157 amd 158.
033805,000010: ## It has been adapted such that the resulting bugger words
033806,000011: ## exactly match those specified for Luminary 163 in NASA
033807,000012: ## drawing 2021152N, which gives relatively high confidence
033808,000013: ## that the reconstruction is correct.
033809,000014: ## Reference: pp. 779-783
033810,000015: ## Assembler: yaYUL
033811,000016: ## Contact: Ron Burkey <info@sandroid.org>.
033812,000017: ## Website: www.ibiblio.org/apollo/index.html
033813,000018: ## Mod history: 2019-08-21 MAS Created from Luminary 173.
033814,000019:
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Page 789
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033816,000021: 31,2144 BANK 31
033817,000022:
033818,000023: 31,2000 SETLOC FTHROT
033819,000024:
033820,000025: 31,2000 BANK
033821,000026:
033822,000027: 31,2144 E7,1612 EBANK= PIF
033823,000028:
033824,000029: 31,2144 COUNT* $$/THROT
033825,000030: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
033826,000031: # HERE FC, DESIRED THRUST, AND FP, PRESENT THRUST, UNWEIGHTED, ARE COMPUTED.
033827,000032:
033828,000033: 31,2144 31245 THROTTLE CA ABDELV # COMPUTE PRESENT ACCELERATION IN UNITS OF
033829,000034: 31,2145 00006 EXTEND # 2(-4) M/CS/CS, SAVING SERVICER TROUBLE
033830,000035: 31,2146 72363 MP /AF/CNST
033831,000036: 31,2147 00006 +3 EXTEND
033832,000037: 31,2150 23607 QXCH RTNHOLD
033833,000038: 31,2151 02344 AFDUMP TC MASSMULT
033834,000039: 31,2152 53470 DXCH FP # FP = PRESENT THRUST
033835,000040: 31,2153 00006 EXTEND
033836,000041: 31,2154 31464 DCA /AFC/
033837,000042: 31,2155 02344 TC MASSMULT
033838,000043: 31,2156 00004 INHINT # PREVENT A DOWNRUPT
033839,000044: 31,2157 55615 TS FC # FC = THRUST DESIRED BY GUIDANCE
033840,000045: 31,2160 53466 DXCH FCODD # FCODD = WHAT IT IS GOING TO GET
033841,000046:
033842,000047:
033843,000048: 31,2161 00006 EXTEND
033844,000049: 31,2162 31234 DCA PIPTIME
033845,000050: 31,2163 53753 DXCH GTCTIME # DOWNLINK TIME AGREEMENT
033846,000051: 31,2164 00003 RELINT
033847,000052:
033848,000053: # COMPUTE DESIRED THRUST FOR DISPLAY AS A PERCENTAGE OF 10,500 POUNDS
033849,000054:
033850,000055: 31,2165 32365 CAF 4FMAXNOM # MOVE 4FMAXNOM TO ERASABLE FOR DV BELOW
033851,000056: 31,2166 54002 TS Q
033852,000057: 31,2167 31615 CA FC
033853,000058: 31,2170 72364 MASK OCT17777 # FOR SAFETY
033854,000059: 31,2171 00006 EXTEND
033855,000060: 31,2172 10002 DV Q
033856,000061: 31,2173 00006 EXTEND
033857,000062: 31,2174 75003 MP 4SECS
033858,000063: 31,2175 55750 TS THRDISP # FOR DISPLAY IN N92
033859,000064:
033860,000065: # IF IT HAS BEEN LESS THAN 3 SECONDS SINCE THE LAST THROTTLING, AUGMENT FP USING THE FWEIGHT CALCULATED THEN.
033861,000066:
033862,000067: 31,2176 41617 CS TTHROT # THIS CODING ASSUMES A FLATOUT WITHIN
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Page 790
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033864,000069: 31,2177 60025 AD TIME1 # 80 SECONDS BEFORE FIRST THROTTLE CALL
033865,000070: 31,2200 74733 MASK POSMAX
033866,000071: 31,2201 40000 COM
033867,000072: 31,2202 65002 AD 3SECS
033868,000073: 31,2203 00006 EXTEND
033869,000074: 31,2204 62210 BZMF WHERETO # BRANCH IF (TIME1-TTHROT +1) > 3 SECONDS
033870,000075: 31,2205 00006 EXTEND
033871,000076: 31,2206 31611 DCA FWEIGHT
033872,000077: 31,2207 21470 DAS FP
033873,000078:
033874,000079:
033875,000080: # THIS LOGIC DETERMINES THE THROTTLING IN THE REGION 10% - 94%. THE MANUAL THROTTLE, NOMINALLY SET AT
033876,000081: # MINIMUM BY ASTRONAUT OR MISSION CONTROL PROGRAMS, PROVIDES THE LOWER BOUND. A STOP IN THE THROTTLE HARDWARE
033877,000082: # PROVIDES THE UPPER.
033878,000083:
033879,000084: 31,2210 35014 WHERETO CA EBANK5 # INITIALIZE L*WCR*T AND H*GHCR*T FROM
033880,000085: 31,2211 54003 TS EBANK # PAD LOADED ERASABLES IN W-MATRIX
033881,000086: 31,2212 E5,1472 EBANK= LOWCRIT
033882,000087: 31,2212 00006 EXTEND
033883,000088: 31,2213 31473 DCA LOWCRIT
033884,000089: 31,2214 52131 DXCH L*WCR*T
033885,000090: 31,2215 35016 CA EBANK7
033886,000091: 31,2216 54003 TS EBANK
033887,000092: 31,2217 E7,1612 EBANK= PIF
033888,000093: 31,2217 44755 CS ZERO # INITIALIZE PIFPSET
033889,000094: 31,2220 55606 TS PIFPSET
033890,000095: 31,2221 40131 CS H*GHCR*T
033891,000096: 31,2222 61620 AD FCOLD
033892,000097: 31,2223 00006 EXTEND
033893,000098: 31,2224 62236 BZMF LOWFCOLD # BRANCH IF FCOLD < OR = HIGHCRIT
033894,000099: 31,2225 40130 CS L*WCR*T
033895,000100: 31,2226 61465 AD FCODD
033896,000101: 31,2227 00006 EXTEND
033897,000102: 31,2230 62233 BZMF FCOMPSET # BRANCH IF FC < OR = LOWCRIT
033898,000103: 31,2231 31467 CA FP # SEE NOTE 1
033899,000104: 31,2232 12243 TCF FLATOUT1
033900,000105:
033901,000106: 31,2233 42002 FCOMPSET CS FMAXODD # SEE NOTE 2
033902,000107: 31,2234 61467 AD FP
033903,000108: 31,2235 12245 TCF FLATOUT2
033904,000109:
033905,000110: 31,2236 40131 LOWFCOLD CS H*GHCR*T
033906,000111: 31,2237 61465 AD FCODD
033907,000112: 31,2240 00006 EXTEND
033908,000113: 31,2241 62246 BZMF DOPIF # BRANCH IF FC < OR = HIGHCRIT
033909,000114:
033910,000115: 31,2242 32003 CA FMAXPOS # NO: THROTTLE-UP
033911,000116: 31,2243 53466 FLATOUT1 DXCH FCODD
033912,000117: 31,2244 34737 CA FEXTRA
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Page 791
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033914,000119: 31,2245 55606 FLATOUT2 TS PIFPSET
033915,000120:
033916,000121: # NOTE 1 FC IS SET EQUAL TO FP SO PIF WILL BE ZERO. THIS IS DESIRABLE
033917,000122: # AS THERE IS ACTUALLY NO THROTTLE CHANGE.
033918,000123:
033919,000124: # NOTE 2 HERE, SINCE WE ARE ABOUT TO RETURN TO THE THROTTLEABLE REGION
033920,000125: # (BELOW 55%) THE QUANTITY -(FMAXODD - FP) IS COMPUTED AND PUT
033921,000126: # INTO PIFPSET TO COMPENSATE FOR THE DIFFERENCE BETWEEN THE
033922,000127: # NUMBER OF BITS CORRESPONDING TO FULL THROTTLE (FMAXODD) AND THE
033923,000128: # NUMBER CORRESPONDING TO ACTUAL THRUST (FP). THUS THE TOTAL
033924,000129: # THROTTLE COMMAND PIF = FC - FP -(FMAXODD - FP) = FC - FMAXODD.
033925,000130:
033926,000131: 31,2246 03747 DOPIF TC FASTCHNG
033927,000132: 31,2247 00006 EXTEND
033928,000133: 31,2250 31466 DCA FCODD
033929,000134: 31,2251 55620 TS FCOLD
033930,000135: 31,2252 53613 DXCH PIF
033931,000136: 31,2253 00006 EXTEND
033932,000137: 31,2254 41470 DCS FP
033933,000138: 31,2255 21613 DAS PIF # PIF = FC - FP, NEVER EQUALS +0
033934,000139:
033935,000140:
033936,000141: 31,2256 31612 DOIT CA PIF
033937,000142: 31,2257 61606 AD PIFPSET # ADD IN PIFPSET, WITHOUT CHANGING PIF
033938,000143: 31,2260 55614 TS PSEUDO55
033939,000144: 31,2261 54055 TS THRUST
033940,000145: 31,2262 34750 CAF BIT4
033941,000146: 31,2263 00006 EXTEND
033942,000147: 31,2264 05014 WOR CHAN14
033943,000148: 31,2265 30025 CA TIME1
033944,000149: 31,2266 55617 TS TTHROT
033945,000150:
033946,000151: # SINCE /AF/ IS NOT AN INSTANTANEOUS ACCELERATION, BUT RATHER AN "AVERAGE" OF THE ACCELERATION LEVELS DURING
033947,000152: # THE PRECEEDING PIPA INTERVAL, AND SINCE FP IS COMPUTED DIRECTLY FROM /AF/, FP IN ORDER TO CORRESPOND TO THE
033948,000153: # ACTUAL THRUST LEVEL AT THE END OF THE INTERVAL MUST BE WEIGHTED BY
033949,000154:
033950,000155: # PIF(PPROCESS + TL) PIF /PIF/
033951,000156: # FWEIGHT = ------------------ + -------------
033952,000157: # PGUID 2 PGUID FRATE
033953,000158:
033954,000159: # WHERE PPROCESS IS THE TIME BETWEEN PIPA READING AND THE START OF THROTTLING, PGUID IS THE GUIDANCE PERIOD, AND
033955,000160: # FRATE IS THE THROTTLING RATE (32 UNITS PER CENTISECOND). PGUID IS EITHER 1 OR 2 SECONDS. THE "TL" IN THE
033956,000161: # FIRST TERM REPRESENTS THE ENGINE'S RESPONSE LAG. HERE FWEIGHT IS COMPUTED FOR USE NEXT PASS.
033957,000162:
033958,000163: 31,2267 31762 CA THISTPIP +1 # INITIALIZE FWEIGHT COMP AS IF FOR P66
033959,000164: 31,2270 54130 TS BUF
033960,000165:
033961,000166: 31,2271 41010 CS MODREG # ARE WE IN FACT IN P66?
033962,000167: 31,2272 62454 AD DEC66
033963,000168: 31,2273 00006 EXTEND
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Page 792
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033965,000170: 31,2274 12301 BZF FWCOMP # YES
033966,000171:
033967,000172: 31,2275 31234 CA PIPTIME +1 # NO: INITIALIZE FOR TWO SECOND PERIOD
033968,000173: 31,2276 54130 TS BUF
033969,000174: 31,2277 35003 CAF 4SECS
033970,000175: 31,2300 12302 TCF FWCOMP +1
033971,000176:
033972,000177: 31,2301 35000 FWCOMP CAF 2SECS
033973,000178: 31,2302 54002 +1 TS Q
033974,000179: 31,2303 00006 EXTEND
033975,000180: 31,2304 74746 MP BIT6
033976,000181: 31,2305 22131 LXCH BUF +1
033977,000182: 31,2306 40130 CS BUF # TIME OF LAST PIPA READING.
033978,000183: 31,2307 60025 AD TIME1
033979,000184: 31,2310 62004 AD THROTLAG # COMPENSATE FOR ENGINE RESPONSE LAG
033980,000185: 31,2311 74357 MASK LOW8 # MAKE SURE SMALL AND POSITIVE
033981,000186: 31,2312 22007 ZL
033982,000187: 31,2313 00006 EXTEND
033983,000188: 31,2314 10002 DV Q
033984,000189: 31,2315 00006 EXTEND
033985,000190: 31,2316 71612 MP PIF
033986,000191: 31,2317 60000 DOUBLE
033987,000192: 31,2320 53611 DXCH FWEIGHT
033988,000193: 31,2321 11612 CCS PIF
033989,000194: 31,2322 64753 AD ONE
033990,000195: 31,2323 12325 TCF +2
033991,000196: 31,2324 64753 AD ONE
033992,000197: 31,2325 00006 EXTEND
033993,000198: 31,2326 71612 MP PIF
033994,000199: 31,2327 00006 EXTEND
033995,000200: 31,2330 10131 DV BUF +1
033996,000201: 31,2331 22007 ZL
033997,000202: 31,2332 21611 DAS FWEIGHT
033998,000203:
033999,000204:
034000,000205: 31,2333 01607 THDUMP TC RTNHOLD
034001,000206:
034002,000207:
034003,000208: # FLATOUT THROTTLES UP THE DESCENT ENGINE, AND IS CALLED AS A BASIC SUBROUTINE.
034004,000209:
034005,000210: 31,2334 34737 FLATOUT CAF BIT13 # 4096 PULSES
034006,000211: 31,2335 55606 WHATOUT TS PIFPSET # USE PIFPSET SO FWEIGHT WILL BE ZERO
034007,000212: 31,2336 44755 CS ZERO
034008,000213: 31,2337 55620 TS FCOLD
034009,000214: 31,2340 55612 TS PIF
034010,000215: 31,2341 00006 EXTEND
034011,000216: 31,2342 23607 QXCH RTNHOLD
034012,000217: 31,2343 12256 TCF DOIT
034013,000218:
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Page 793
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034015,000220: # MASSMULT SCALES ACCELERATION, ARRIVING IN A AND L IN UNITS OF 2(-4) M/CS/CS, TO FORCE IN PULSE UNITS.
034016,000221:
034017,000222: 31,2344 00006 MASSMULT EXTEND
034018,000223: 31,2345 22130 QXCH BUF
034019,000224: 31,2346 52155 DXCH MPAC
034020,000225: 31,2347 07106 TC DMP
034021,000226: 31,2350 01243 ADRES MASS
034022,000227: 31,2351 07106 TC DMP # LEAVES PROPERLY SCALED FORCE IM MPAC
034023,000228: 31,2352 02005 ADRES SCALEFAC
034024,000229: 31,2353 07262 TC TPAGREE
034025,000230: 31,2354 30154 CA MPAC
034026,000231: 31,2355 00006 EXTEND
034027,000232: 31,2356 12361 BZF +3
034028,000233: 31,2357 34733 CAF POSMAX
034029,000234: 31,2360 00130 TC BUF
034030,000235: 31,2361 52156 DXCH MPAC +1
034031,000236: 31,2362 00130 TC BUF
034032,000237:
034033,000238:
034034,000239: # CONSTANTS:-
034035,000240:
034036,000241: 31,2363 4737 FEXTRA = BIT13 # FEXT +5.13309020 E+4
034037,000242:
034038,000243: 31,2363 04143 /AF/CNST DEC .13107
034039,000244:
034040,000245: 31,2364 17777 OCT17777 OCT 17777
034041,000246: 31,2365 35074 4FMAXNOM DEC 14908 B-14 # EQUIVALENT TO 10,500 LBS.
034042,000247: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
End of include-file THROTTLE_CONTROL_ROUTINES.agc. Parent file is MAIN.agc