Source Code
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These source-code files are part of a reconstructed copy of Skylark 048, the
Block II Command Module (CM) Apollo Guidance Computer (AGC) software for the
Skylab-2, Skylab-3, Skylab-4, and Apollo-Soyuz Test Project missions.
They have been created via disassembly of binary dumps of the original core rope
memory modules actually flown on Skylab-2, part numbers 2010802-541, 2010802-551,
2010802-561, 2010802-571, 2010802-581, and 2010802-591. Access to these modules
was provided by the New Mexico Museum of Space History, who we are much indebted to.
The source code for the Apollo 15, 16, and 17 software, Artemis 072, was used as
a starting point. Heavy use was made of TRW 4900.5-244, Programmed Guidance Equations
for Skylark Command Module Earth Orbital Program, dated 14 February 1972. This document
contains pseudocode of essentially all of Skylark, using original program labels which
have been copied for this source reconstruction.
Since only binary dumps (rather than listings) of Skylark are available as source material,
all comments and labels are approximate.
They have been taken from the Programmed Guidance Equations or other AGC programs where
possible, or, in some places, written from scratch to match what we believe would have
been in the original listing.
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039931,000002: ## Copyright: Public domain.
039932,000003: ## Filename: MYSUBS.agc
039933,000004: ## Purpose: A section of Skylark revision 048.
039934,000005: ## It is part of the source code for the Apollo Guidance Computer (AGC)
039935,000006: ## for Skylab-2, Skylab-3, Skylab-4, and ASTP. No original listings of
039936,000007: ## this software are available; instead, this file was created via
039937,000008: ## disassembly of dumps of the core rope modules actually flown on
039938,000009: ## Skylab-2. Access to these modules was provided by the New Mexico
039939,000010: ## Museum of Space History.
039940,000011: ## Assembler: yaYUL
039941,000012: ## Contact: Ron Burkey <info@sandroid.org>.
039942,000013: ## Website: www.ibiblio.org/apollo/index.html
039943,000014: ## Mod history: 2023-09-04 MAS Created from Artemis 072.
039944,000015:
039945,000016:
039946,000017: 21,2000 SETLOC MYSUBS
039947,000018: 21,2000 BANK
039948,000019:
039949,000020: 21,2000 E6,1537 EBANK= KMPAC
039950,000021: 21,2000 5073 SPCOS1 EQUALS SPCOS
039951,000022: 21,2000 5074 SPSIN1 EQUALS SPSIN
039952,000023: 21,2000 5073 SPCOS2 EQUALS SPCOS
039953,000024: 21,2000 5074 SPSIN2 EQUALS SPSIN
039954,000025:
039955,000026: 21,2000 COUNT* $$/DAPMS
039956,000027:
039957,000028: # ONE AND ONE HALF PRECISION MULTIPLICATION ROUTINE
039958,000029:
039959,000030: 21,2000 55541 SMALLMP TS KMPTEMP # A(X+Y)
039960,000031: 21,2001 00006 EXTEND
039961,000032: 21,2002 71540 MP KMPAC +1
039962,000033: 21,2003 55540 TS KMPAC +1 # AY
039963,000034: 21,2004 35003 CAF ZERO
039964,000035: 21,2005 57537 XCH KMPAC
039965,000036: 21,2006 00006 EXTEND
039966,000037: 21,2007 71541 MP KMPTEMP # AX
039967,000038: 21,2010 21540 DAS KMPAC # AX+AY
039968,000039: 21,2011 00002 TC Q
039969,000040:
039970,000041: # SUBROUTINE FOR DOUBLE PRECISION ADDITIONS OF ANGLES
039971,000042: # A AND L CONTAIN A DP(1S) ANGLE SCALED BY 180 DEGS TO BE ADDED TO KMPAC.
039972,000043: # RESULT IS PLACED IN KMPAC. TIMING = 6 MCT (22 MCT ON OVERFLOW)
039973,000044:
039974,000045: 21,2012 21540 DPADD DAS KMPAC
039975,000046: 21,2013 00006 EXTEND
039976,000047: 21,2014 12031 BZF TSK +1 # NO OVERFLOW
039977,000048: 21,2015 11537 CCS KMPAC
039978,000049: 21,2016 12032 TCF DPADD+ # + OVERFLOW
039979,000050: 21,2017 12021 TCF +2
039980,000051: 21,2020 12034 TCF DPADD- # - OVERFLOW
039981,000052: 21,2021 11540 CCS KMPAC +1
039982,000053: 21,2022 12037 TCF DPADD2+ # UPPER = 0, LOWER +
039983,000054: 21,2023 12025 TCF +2
039984,000055: 21,2024 40000 COM # UPPER = 0, LOWER -
039985,000056: 21,2025 64761 AD POSMAX # LOWER = 0, A=0
039986,000057: 21,2026 55540 TS KMPAC +1 # CAN NOT OVERFLOW
039987,000058: 21,2027 34761 CA POSMAX # UPPER WAS = 0
039988,000059: 21,2030 55537 TSK TS KMPAC
039989,000060: 21,2031 00002 +1 TC Q
039990,000061: 21,2032 64763 DPADD+ AD NEGMAX # KMPAC GREATER THAN 0
039991,000062: 21,2033 12030 TCF TSK
039992,000063:
039993,000064: 21,2034 40000 DPADD- COM
039994,000065: 21,2035 64761 AD POSMAX # KMPAC LESS THAN 0
039995,000066: 21,2036 12030 TCF TSK
039996,000067:
039997,000068: 21,2037 64763 DPADD2+ AD NEGMAX # CAN NOT OVERFLOW
039998,000069: 21,2040 55540 TS KMPAC +1
039999,000070: 21,2041 34763 CA NEGMAX # UPPER WAS = 0
040000,000071: 21,2042 12030 TCF TSK
End of include-file MYSUBS.agc. Parent file is MAIN.agc