Source Code
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These source-code files are part of a reconstructed copy of Luminary 97, the
original release of the Apollo 11 Lunar Module (LM) Apollo Guidance Computer
(AGC) software.
The reconstruction began with source code of Luminary 99 revision 1 previously
transcribed from a digitized copy of that program. The code was then updated
by undoing changes described in original Luminary memos 83 and 85, using asterisks
indicating changed lines in the listing as a guide. The reconstruction was
verified by matching memory-bank checksums to those listed in drawing 2021152D.
Note that page numbers in the reconstructed code match those on the Luminary 099
revision 001 printout, although the added code would likely have changed page
numbers for a real Luminary 97 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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033774,000002: ## Copyright: Public domain.
033775,000003: ## Filename: THROTTLE_CONTROL_ROUTINES.agc
033776,000004: ## Purpose: A section of Luminary revision 97.
033777,000005: ## It is part of the reconstructed source code for the
033778,000006: ## original release of the flight software for the Lunar
033779,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
033780,000008: ## The code has been recreated from a copy of Luminary 99
033781,000009: ## revision 001, using asterisks indicating changed lines in
033782,000010: ## the listing and Luminary Memos #83 and #85, which list
033783,000011: ## changes between Luminary 97 and 98, and 98 and 99. The
033784,000012: ## code has been adapted such that the resulting bugger words
033785,000013: ## exactly match those specified for Luminary 97 in NASA drawing
033786,000014: ## 2021152D, which gives relatively high confidence that the
033787,000015: ## reconstruction is correct.
033788,000016: ## Reference: pp. 793-797
033789,000017: ## Assembler: yaYUL
033790,000018: ## Contact: Ron Burkey <info@sandroid.org>.
033791,000019: ## Website: www.ibiblio.org/apollo/index.html
033792,000020: ## Mod history: 2019-07-28 MAS Created from Luminary 99.
033793,000021:
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Page 793
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033795,000023: 31,2216 BANK 31
033796,000024: 31,2000 SETLOC FTHROT
033797,000025: 31,2000 BANK
033798,000026: 31,2216 E7,1612 EBANK= PIF
033799,000027: 31,2216 COUNT* $$/THROT
033800,000028:
033801,000029: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
033802,000030: # HERE FC, DESIRED THRUST, AND FP, PRESENT THRUST, UNWEIGHTED, ARE COMPUTED.
033803,000031:
033804,000032: 31,2216 31246 THROTTLE CA ABDELV # COMPUTE PRESENT ACCELERATION IN UNITS OF
033805,000033: 31,2217 00006 EXTEND # 2(-4) M/CS/CS, SAVING SERVICER TROUBLE
033806,000034: 31,2220 72417 MP /AF/CNST
033807,000035: 31,2221 00006 +3 EXTEND
033808,000036: 31,2222 23607 QXCH RTNHOLD
033809,000037: 31,2223 02400 AFDUMP TC MASSMULT
033810,000038: 31,2224 53470 DXCH FP # FP = PRESENT THRUST
033811,000039: 31,2225 00006 EXTEND
033812,000040: 31,2226 31464 DCA /AFC/
033813,000041: 31,2227 02400 TC MASSMULT
033814,000042: 31,2230 55615 TS FC # FC = THRUST DESIRED BY GUIDANCE
033815,000043: 31,2231 53466 DXCH FCODD # FCODD = WHAT IT IS GOING TO GET
033816,000044:
033817,000045: # IF IT HAS BEEN LESS THAN 3 SECONDS SINCE THE LAST THROTTLING, AUGMENT FP USING THE FWEIGHT CALCULATED THEN.
033818,000046:
033819,000047: 31,2232 41617 CS TTHROT # THIS CODING ASSUMES A FLATOUT WITHIN
033820,000048: 31,2233 60025 AD TIME1 # 80 SECONDS BEFORE FIRST THROTTLE CALL
033821,000049: 31,2234 74733 MASK POSMAX
033822,000050: 31,2235 40000 COM
033823,000051: 31,2236 65002 AD 3SECS
033824,000052: 31,2237 00006 EXTEND
033825,000053: 31,2240 62244 BZMF WHERETO # BRANCH IF (TIME1-TTHROT +1) > 3 SECONDS
033826,000054: 31,2241 00006 EXTEND
033827,000055: 31,2242 31611 DCA FWEIGHT
033828,000056: 31,2243 21470 DAS FP
033829,000057:
033830,000058: # THIS LOGIC DETERMINES THE THROTTLING IN THE REGION 10% - 94%. THE MANUAL THROTTLE, NOMINALLY SET AT
033831,000059: # MINIMUM BY ASTRONAUT OR MISSION CONTROL PROGRAMS, PROVIDES THE LOWER BOUND. A STOP IN THE THROTTLE HARDWARE
033832,000060: # PROVIDES THE UPPER.
033833,000061:
033834,000062: 31,2244 35014 WHERETO CA EBANK5 # INITIALIZE L*WCR*T AND H*GHCR*T FROM
033835,000063: 31,2245 54003 TS EBANK # PAD LOADED ERASABLES IN W-MATRIX
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Page 794
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033837,000065: 31,2246 E5,1506 EBANK= LOWCRIT
033838,000066: 31,2246 00006 EXTEND
033839,000067: 31,2247 31507 DCA LOWCRIT
033840,000068: 31,2250 52131 DXCH L*WCR*T
033841,000069: 31,2251 35016 CA EBANK7
033842,000070: 31,2252 54003 TS EBANK
033843,000071: 31,2253 E7,1612 EBANK= PIF
033844,000072: 31,2253 44755 CS ZERO # INITIALIZE PIFPSET
033845,000073: 31,2254 55606 TS PIFPSET
033846,000074: 31,2255 40131 CS H*GHCR*T
033847,000075: 31,2256 61620 AD FCOLD
033848,000076: 31,2257 00006 EXTEND
033849,000077: 31,2260 62272 BZMF LOWFCOLD # BRANCH IF FCOLD < OR = HIGHCRIT
033850,000078: 31,2261 40130 CS L*WCR*T
033851,000079: 31,2262 61465 AD FCODD
033852,000080: 31,2263 00006 EXTEND
033853,000081: 31,2264 62267 BZMF FCOMPSET # BRANCH IF FC < OR = LOWCRIT
033854,000082: 31,2265 31467 CA FP # SEE NOTE 1
033855,000083: 31,2266 12277 TCF FLATOUT1
033856,000084:
033857,000085: 31,2267 42002 FCOMPSET CS FMAXODD # SEE NOTE 2
033858,000086: 31,2270 61467 AD FP
033859,000087: 31,2271 12301 TCF FLATOUT2
033860,000088:
033861,000089: 31,2272 40131 LOWFCOLD CS H*GHCR*T
033862,000090: 31,2273 61465 AD FCODD
033863,000091: 31,2274 00006 EXTEND
033864,000092: 31,2275 62302 BZMF DOPIF # BRANCH IF FC < OR = HIGHCRIT
033865,000093:
033866,000094: 31,2276 32003 CA FMAXPOS # NO: THROTTLE-UP
033867,000095: 31,2277 53466 FLATOUT1 DXCH FCODD
033868,000096: 31,2300 34737 CA FEXTRA
033869,000097: 31,2301 55606 FLATOUT2 TS PIFPSET
033870,000098:
033871,000099: # NOTE 1 FC IS SET EQUAL TO FP SO PIF WILL BE ZERO. THIS IS DESIRABLE
033872,000100: # AS THERE IS ACTUALLY NO THROTTLE CHANGE.
033873,000101:
033874,000102: # NOTE2 HERE, SINCE WE ARE ABOUT TO RETURN TO THE THROTTLEABLE REGION
033875,000103: # (BELOW 55%) THE QUANTITY -(FMAXODD-FP) IS COMPUTED AND PUT
033876,000104: # INTO PIFPSET TO COMPENSATE FOR THE DIFFERENCE BETWEEN THE
033877,000105: # NUMBER OF BITS CORRESPONDING TO FULL THROTTLE (FMAXODD) AND THE
033878,000106: # NUMBER CORRESPONDING TO ACTUAL THRUST (FP). THUS THE TOTAL
033879,000107: # THROTTLE COMMAND PIF = FC - FP - (FMAXODD - FP) = FC - FMAXODD.
033880,000108:
033881,000109: 31,2302 03740 DOPIF TC FASTCHNG
033882,000110: 31,2303 00006 EXTEND
033883,000111: 31,2304 31466 DCA FCODD
033884,000112: 31,2305 55620 TS FCOLD
033885,000113: 31,2306 53613 DXCH PIF
033886,000114: 31,2307 00006 EXTEND
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Page 795
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033888,000116: 31,2310 41470 DCS FP
033889,000117: 31,2311 21613 DAS PIF # PIF = FC - FP, NEVER EQUALS +0
033890,000118:
033891,000119: 31,2312 31612 DOIT CA PIF
033892,000120: 31,2313 61606 AD PIFPSET # ADD IN PIFPSET, WITHOUT CHANGING PIF
033893,000121: 31,2314 55614 TS PSEUDO55
033894,000122: 31,2315 54055 TS THRUST
033895,000123: 31,2316 34750 CAF BIT4
033896,000124: 31,2317 00006 EXTEND
033897,000125: 31,2320 05014 WOR CHAN14
033898,000126: 31,2321 30025 CA TIME1
033899,000127: 31,2322 55617 TS TTHROT
033900,000128:
033901,000129: # SINCE /AF/ IS NOT AN INSTANTANEOUS ACCELERATION, BUT RATHER AN "AVERAGE" OF THE ACCELERATION LEVELS DURING
033902,000130: # THE PRECEEDING PIPA INTERVAL, AND SINCE FP IS COMPUTED DIRECTLY FROM /AF/, FP IN ORDER TO CORRESPOND TO THE
033903,000131: # ACTUAL THRUST LEVEL AT THE END OF THE INTERVAL MUST BE WEIGHTED BY
033904,000132:
033905,000133: # PIF(PPROCESS + TL) PIF /PIF/
033906,000134: # FWEIGHT = ------------------ + -------------
033907,000135: # PGUID 2 PGUID FRATE
033908,000136:
033909,000137: # WHERE PPROCESS IS THE TIME BETWEEN PIPA READING AND THE START OF THROTTLING, PGUID IS THE GUIDANCE PERIOD, AND
033910,000138: # FRATE IS THE THROTTLING RATE (32 UNITS PER CENTISECOND). PGUID IS EITHER 1 OR 2 SECONDS. THE "TL" IN THE
033911,000139: # FIRST TERM REPRESENTS THE ENGINE'S RESPONSE LAG. HERE FWEIGHT IS COMPUTED FOR USE NEXT PASS.
033912,000140:
033913,000141: 31,2323 31762 CA THISTPIP +1 # INITIALIZE FWEIGHT COMP AS IF FOR P66
033914,000142: 31,2324 54130 TS BUF
033915,000143:
033916,000144: 31,2325 41011 CS MODREG # ARE WE IN FACT IN P66?
033917,000145: 31,2326 62501 AD DEC66
033918,000146: 31,2327 00006 EXTEND
033919,000147: 31,2330 12335 BZF FWCOMP # YES
033920,000148:
033921,000149: 31,2331 31235 CA PIPTIME +1 # NO: INITIALIZE FOR TWO SECOND PERIOD
033922,000150: 31,2332 54130 TS BUF
033923,000151: 31,2333 35003 CAF 4SECS
033924,000152: 31,2334 12336 TCF FWCOMP +1
033925,000153:
033926,000154: 31,2335 35000 FWCOMP CAF 2SECS
033927,000155: 31,2336 54002 +1 TS Q
033928,000156: 31,2337 00006 EXTEND
033929,000157: 31,2340 74746 MP BIT6
033930,000158: 31,2341 22131 LXCH BUF +1
033931,000159: 31,2342 40130 CS BUF # TIME OF LAST PIPA READING.
033932,000160: 31,2343 60025 AD TIME1
033933,000161: 31,2344 62004 AD THROTLAG # COMPENSATE FOR ENGINE RESPONSE LAG
033934,000162: 31,2345 74357 MASK LOW8 # MAKE SURE SMALL AND POSITIVE
033935,000163: 31,2346 22007 ZL
033936,000164: 31,2347 00006 EXTEND
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Page 796
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033938,000166: 31,2350 10002 DV Q
033939,000167: 31,2351 00006 EXTEND
033940,000168: 31,2352 71612 MP PIF
033941,000169: 31,2353 60000 DOUBLE
033942,000170: 31,2354 53611 DXCH FWEIGHT
033943,000171: 31,2355 11612 CCS PIF
033944,000172: 31,2356 64753 AD ONE
033945,000173: 31,2357 12361 TCF +2
033946,000174: 31,2360 64753 AD ONE
033947,000175: 31,2361 00006 EXTEND
033948,000176: 31,2362 71612 MP PIF
033949,000177: 31,2363 00006 EXTEND
033950,000178: 31,2364 10131 DV BUF +1
033951,000179: 31,2365 22007 ZL
033952,000180: 31,2366 21611 DAS FWEIGHT
033953,000181:
033954,000182: 31,2367 01607 THDUMP TC RTNHOLD
033955,000183:
033956,000184: # FLATOUT THROTTLES UP THE DESCENT ENGINE, AND IS CALLED AS A BASIC SUBROUTINE.
033957,000185:
033958,000186: 31,2370 34737 FLATOUT CAF BIT13 # 4096 PULSES
033959,000187: 31,2371 55606 WHATOUT TS PIFPSET # USE PIFPSET SO FWEIGHT WILL BE ZERO
033960,000188: 31,2372 44755 CS ZERO
033961,000189: 31,2373 55620 TS FCOLD
033962,000190: 31,2374 55612 TS PIF
033963,000191: 31,2375 00006 EXTEND
033964,000192: 31,2376 23607 QXCH RTNHOLD
033965,000193: 31,2377 12312 TCF DOIT
033966,000194:
033967,000195: # MASSMULT SCALES ACCELERATION, ARRIVING IN A AND L IN UNITS OF 2(-4) M/CS/CS, TO FORCE IN PULSE UNITS.
033968,000196:
033969,000197: 31,2400 00006 MASSMULT EXTEND
033970,000198: 31,2401 22130 QXCH BUF
033971,000199: 31,2402 52155 DXCH MPAC
033972,000200: 31,2403 07103 TC DMP
033973,000201: 31,2404 01244 ADRES MASS
033974,000202: 31,2405 07103 TC DMP # LEAVES PROPERLY SCALED FORCE IM MPAC
033975,000203: 31,2406 02005 ADRES SCALEFAC
033976,000204: 31,2407 07257 TC TPAGREE
033977,000205: 31,2410 30154 CA MPAC
033978,000206: 31,2411 00006 EXTEND
033979,000207: 31,2412 12415 BZF +3
033980,000208: 31,2413 34733 CAF POSMAX
033981,000209: 31,2414 00130 TC BUF
033982,000210: 31,2415 52156 DXCH MPAC +1
033983,000211: 31,2416 00130 TC BUF
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Page 797
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033985,000213: # CONSTANTS:-
033986,000214:
033987,000215: 31,2417 4737 FEXTRA = BIT13 # FEXT +5.13309020 E+4
033988,000216:
033989,000217: 31,2417 04143 /AF/CNST DEC .13107
033990,000218:
033991,000219: # * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
End of include-file THROTTLE_CONTROL_ROUTINES.agc. Parent file is MAIN.agc