FINDCDUW--GUIDAP_INTERFACE.agc
# Copyright: Public domain.
# Filename: FINDCDUW--GUIDAP_INTERFACE.agc
# Purpose: Part of the source code for Luminary 1A build 099.
# It is part of the source code for the Lunar Module's (LM)
# Apollo Guidance Computer (AGC), for Apollo 11.
# Assembler: yaYUL
# Contact: Hartmuth Gutsche <hgutsche@xplornet.com>.
# Website: www.ibiblio.org/apollo.
# Pages: 908-925
# Mod history: 2009-05-28 HG Transcribed from page images.
#
# This source code has been transcribed or otherwise adapted from
# digitized images of a hardcopy from the MIT Museum. The digitization
# was performed by Paul Fjeld, and arranged for by Deborah Douglas of
# the Museum. Many thanks to both. The images (with suitable reduction
# in storage size and consequent reduction in image quality as well) are
# available online at www.ibiblio.org/apollo. If for some reason you
# find that the images are illegible, contact me at info@sandroid.org
# about getting access to the (much) higher-quality images which Paul
# actually created.
#
# Notations on the hardcopy document read, in part:
#
# Assemble revision 001 of AGC program LMY99 by NASA 2021112-061
# 16:27 JULY 14, 1969
# Page 908
# PROGRAM NAME: FINDCDUW
# MOD NUMBER: 1 68-07-15
# MOD AUTHOR: KLUMPP
#
# OBJECTS OF MOD: 1. TO SUPPLY COMMANDED GIMBAL ANGLES FOR NOUN 22.
# 2. TO MAINTAIN CORRECT AND CURRENT THRUST
# DIRECTION DATA IN ALL MODES. THIS IS DONE BY
# FETCHING FOR THE THRUST DIRECTION FILTER THE
# CDUD'S IN PNGCS-AUTO, THE CDU'S IN ALL OTHER
# MODES.
# 3. TO SUBSTITUDE A STOPRATE FOR THE NORMAL
# AUTOPILOT COMMANDS WHENEVER
# 1) NOT IN PNGCS-AUTO, OR
# 2) ENGINE IS OFF.
#
# FUNCTIONAL DESCRIPTION:
#
# FINDCDUW PROVIDES THE INTERFACES BETWEEN THE VARIOUS POWERED FLITE GUIDANCE PROGRAMS
# AND THE DIGITAL AUTOPILOT. THE INPUTS TO FINDCDUW ARE THE THRUST COMMAND VECTOR
# AND THE WINDOW COMMAND VECTOR, AND THE OUTPUTS ARE THE GIMBAL ANGLE
# INCREMENTS, THE COMMANDED ATTITUDE ANGLE RATES, AND THE COMMANDED
# ATTITUDE LAG ANGLES (WHICH ACCOUNT FOR THE ANGLES BY WHICH THE BODY WILL
# LAG BEHIND A RAMP COMMAND IN ATTITUDE ANGLE DUE TO THE FINITE ANGULAR
# ACCELERATIONS AVAILABLE).
#
# FINDCDUW ALIGNS THE ESTIMATED THRUST VECTOR FROM THE THRUST DIRECTION
# FILTER WITH THE THRUST COMMAND VECTOR, AND, WHEN XDVINHIB SET,
# ALIGNS THE +Z HALF OF THE LM ZX PLANE WITH THE WINDOW COMMAND VECTOR.
#
# Page 909
# SPECIFICATIONS:
#
# INITIALIZATION: A SINGLE INTERPRETIVE CALL TO INITCDUW IS REQUIRED
# BEFORE EACH GUIDED MANEUVER USING FINDCDUW.
#
# CALL: INTERPRETIVE CALL TO FINDCDUW WITH THE THRUST COMMAND
# VECTOR IN MPAC. INTERPRETIVE CALL TO FINDCDUW -2 WITH
# THE THRUST COMMAND VECTOR IN UNFC/2 AND NOT IN MPAC.
#
# RETURNS: NORMAL INTERPRETIVE IN ALL CASES
# 1. NORMALLY ALL AUTOPILOT CMDS ARE ISSUED.
# 2. IF NOT PNGCS AUTO, DO STOPRATE AND RETURN
# WITHOUT ISSUING AUTOPILOT CMDS.
# 3. IF ENGINE OFF, DO STOPRATE AND RETURN WITHOUT
# ISSUING AUTOPILOT CMDS.
#
# ALARMS: 00401 IF INPUTS DETERMINE AN ATTITUDE IN GIMBAL LOCK.
# FINDCDUW DRIVES CDUXD AND CDUYD TO THE RQD VALUES,
# BUT DRIVES CDUZD ONLY TO THE GIMBAL LOCK CONE.
#
# 00402 IF UNFC/2 OR UNWC/2 PRODUCE OVERFLOW WHEN
# UNITIZED USING NORMUNIT. FINDCDUW ISSUES
# STOPRATE AS ONLY INPUT TO AUTOPILOT.
#
# INPUTS: UNFC/2 THRUST COMMAND VECTOR, NEED NOT BE SEMI-UNIT.
# UNWC/2 WINDOW COMMAND VECTOR, NEED NOT BE SEMI-UNIT.
# OGABIAS POSSIBLE BIAS FOR OUTER GIMBAL ANGLE (ZEROED IN INITCDUW), UNITS OF PI.
# XOVINHIB FLAG DENOTING X AXIS OVERRIDE INHIBITED.
# CSMDOCKD FLAG DENOTING CSM DOCKED.
# STEERSW FLAG DENOTING INSUFF THRUST FOR THRUST DIR FLTR.
#
# OUTPUTS: DELCDUX,Y,Z
# OMEGAPD,+1,+2
# DELPEROR,+1,+2
# CPHI,+1,+2 FOR NOUN22
#
# DEBRIS: FINDCDUW DESTROYS SINCDUX,Y,Z AND COSCDUX,Y,Z BY
# WRITING INTO THESE LOCATIONS THE SINES AND COSINES
# OF THE CDUD'S IN PNGCS-AUTO, OF THE CDU'S OTHERWISE.
# Page 910
# INITIALIZATION FOR FINDCDUW
BANK 30
SETLOC FCDUW
BANK
EBANK= ECDUW
COUNT* $$/FCDUW
INITCDUW VLOAD
UNITX
STORE UNFV/2
STORE UNWC/2
RVQ
# FINDCDUW PRELIMINARIES
VLOAD # FINDCDUW -2: ENTRY WHEN UNFC/2 PRE-STORD
UNFC/2 # INPUT VECTORS NEED NOT BE SEMI-UNIT
FINDCDUW BOV SETPD # FINDCDUW: ENTRY WHEN UNFC/2 IN MPAC
FINDCDUW # INTERPRETER NOW INITIALIZED
22 # LOCS 0 THRU 21 FOR DIRECTION COSINE MAT
STQ EXIT
QCDUWUSR # SAVE RETURN ADDRESS
# MORE HAUSKEEPING
CA ECDUWL
XCH EBANK # SET EBANK
TS ECDUWUSR # SAVE USER'S EBANK
CA DAPBOOLS
MASK CSMDOCKD # CSMDOCKD MUST NOT BE BIT15
CCS A
CA ONE # INDEX IF CSM DOCKED
TS NDXCDUW
CA XOVINHIB # XOVINHIB MUST NOT BE BIT15
TS FLPAUTNO # SET TO POS-NON-ZERO FLAG PNGCS AUTO NOT
MASK DAPBOOLS
TS FLAGOODW # FLAG0ODW = ANY PNZ NUMBER IF XOV INHIBTD
# Page 911
# FETCH BASIC DATA
INHINT # RELINT AT PAUTNO (TC INTPRET)
CA CDUX # FETCH CDUX,CDUY,CDUZ IN ALL CASES, BUT
TS CDUSPOTX # REPLACE BELOW IF PNGCS AUTO
CA CDUY
TS CDUSPOTY
CA CDUZ
TS CDUSPOTZ
CA BIT10 # PNGCS CONTROL BIT
EXTEND
RAND CHAN30
CCS A
TCF PAUTNO # NOT PNGCS (BITS INVERTED)
CA BIT14 # AUTO MODE BIT
EXTEND
RAND CHAN31
CCS A
TCF PAUTNO # NOT AUTO (BITS INVERTED)
TS FLPAUTNO # RESET FLAG PNGCS AUTO NOT
CA CDUXD # PNGCS AUTO: FETCH CDUXD,CDUYD,CDUZD
TS CDUSPOTX
CA CDUYD
TS CDUSPOTY
CA CDUZD
TS CDUSPOTZ
# Page 912
# FETCH INPUTS
PAUTNO TC INTPRET # ENTERING THRUST CMD STILL IN MPAC
RTB
NORMUNIT
STOVL UNX/2 # SEMI-UNIT THRUST CMD AS INITIAL UNX/2
UNWC/2
RTB RTB
NORMUNIT
QUICTRIG # ALWAYS RQD TO OBTAIN TRIGS OF CDUD'S
STOVL UNZ/2 # SEMI-UNIT WINDOW CMD AS INITIAL UNZ/2
DELV
BOVB UNIT
NOATTCNT # AT LEAST ONE ENTERING CMD VCT ZERO
BOV CALL
AFTRFLTR # IF UNIT DELV OVERFLOWS SKIP FILTER
*SMNB* # YIELDS UNIT(DELV) IN VEH COORDS FOR FLTR
# THRUST DIRECTION FILTER
EXIT
CA UNFVY/2 # FOR RESTARTS, UNFV/2 ALWAYS INTACT, MPAC
LXCH MPAC +3 # RENEWD AFTER RETURN FROM CALLER,
TC FLTRSUB # TWO FILTER UPDATES MAY BE DONE.
TS UNFVY/2 # UNFV/2 NEED NOT BE EXACTLY SEMI-UNIT.
CA UNFVZ/2
LXCH MPAC +5
TC FLTRSUB
TS UNFVZ/2
TC INTPRET # COMPLETES FILTER
# Page 913
# FIND A SUITABLE WINDOW POINTING VECTOR
AFTRFLTR SLOAD BHIZ # IF XOV NOT INHIBITED, GO FETCH ZNB
FLAGOODW
FETCHZNB
VLOAD CALL
UNZ/2
UNWCTEST
FETCHZNB VLOAD
ZNBPIP
STCALL UNZ/2
UNWCTEST
VLOAD VCOMP # Z AND -X CAN'T BOTH PARALLEL UNFC/2
XNBPIP
STORE UNZ/2
# COMPUTE THE REQUIRED DIRECTION COSINE MATRIX
DCMCL VLOAD VXV
UNZ/2
UNX/2
UNIT PUSH # UNY/2 FIRST ITERATION
VXV VSL1
UNX/2
STORE UNZ/2 # -UNZ/2 FIRST ITERATION
VXSC PDVL # EXCHANGE -UNFVZ/2 UNZ/2 FOR UNY/2
UNFVZ/2 # MUST BE SMALL
VXSC BVSU # YIELDS -UNFVY/2 UNY/2-UNFVZ/2 UNZ/2
UNFVY/2 # MUST BE SMALL
VSL1 VAD
UNX/2
UNIT # TOTALLY ELIMINATES THRUST POINTING ERROR
STORE UNX/2 # UNX/2
VXV VSL1
UNZ/2 # -UNZ/2 WAS STORED HERE REMEMBER
STORE UNY/2 # UNY/2
VCOMP VXV
UNX/2
VSL1
STORE UNZ/2 # UNZ/2
# Page 914
# COMPUTES THE REQUIRED GIMBAL ANGLES
CALL
NB2CDUSP # YIELDS THE RQD GIMBAL ANGLES, 2'S, PI
EXIT
# LIMIT THE MIDDLE GIMBAL ANGLE & COMPUTE THE UNLIMITED GIMBAL ANGLE CHGS
CA MPAC +2 # LIMIT THE MGA
TS L # CAN'T LXCH: NEED UNLIMITED MGA FOR ALARM
CA CDUZDLIM
TC LIMITSUB # YIELDS LIMITED MGA. 1 BIT ERROR POSSIBLE
XCH MPAC +2 # BECAUSE USING 2'S COMP. WHO CARES?
EXTEND
MSU MPAC +2 # THIS BETTER YIELD ZERO
EXTEND
BZF +2
TCF ALARMMGA
MGARET INHINT # RELINT AT TC INTPRET AFTER TCQCDUW
ZL
CA TWO
DELGMBLP TS TEM2
CA L # TO PREVENT FALSE STARTS ABOUT X, ZERO
EXTEND # FLAGOODW IF DELGMBZ OR Y TOO BIG.
SQUARE
AD HI5 # WITHIN 1 BIT OF -(45 DEG SQUARED)
EXTEND
BZMF +3
CA ZERO
TS FLAGOODW
INDEX TEM2
CA MPAC
INDEX TEM2
TS CPHI # OUTPUTS TO NOUN22
EXTEND
INDEX TEM2
MSU CDUXD # NO MATTER THAT THESE SLIGHTLY DIFFERENT
COM # FROM WHEN WE INITIALLY FETCHED THEM
INDEX TEM2
TS -DELGMB # -UNLIMITED GIMBAL ANGLE CHGS, 1'S, PI
TS L # FOR PRECEDING TEST ON NEXT LOOP PASS
CCS TEM2
TCF DELGMBLP
# Page 915
# BRANCHES TO NOATTCNT
CCS FLPAUTNO
TCF NOATTCNT +2 # NO PNGCS AUTO
CA FLAGWRD5
MASK ENGONBIT
EXTEND
BZF NOATTCNT +2 # ENGINE NOT ON
# Page 916
# LIMIT THE ATTITUDE ANGLE CHANGES
#
# THIS SECTION LIMITS THE ATTITUDE ANGLE CHANGES ABOUT A SET OF ORTHOGONAL VEHICLE AXES X,YPRIME,ZPRIME,
# THESE AXES COINCIDE WITH THE COMMANDED VEHICLE AXES IF AND ONLY IF CDUXD IS ZERO. THE PRIME SYSTEM IS
# THE COMMANDED VEHICLE SYSTEM ROTATED ABOUT THE X AXIS TO BRING THE Z AXIS INTO ALIGNMENT WITH THE MIDDLE GIMBAL
# AXIS. ATTITUDE ANGLE CHANGES IN THE PRIME SYSTEM ARE RELATED TO SMALL GIMBAL ANGLE CHANGES BY:
#
# [ -DELATTX ] [ 1 SIN(CDUZD) 0 ] [ -DELGMBX ]
# [ ] [ ] [ ]
# [ -DELATTYPRIME ] = [ 0 COS(CDUZD) 0 ] [ -DELGMBY ]
# [ ] [ ] [ ]
# [ -DELATTZPRIME ] [ 0 0 1 ] [ -DELGMBZ ]
LXCH -DELGMB +2 # SAME AS -DELATTZPRIME UNLIMITED
INDEX NDXCDUW
CA DAZMAX
TC LIMITSUB
TS -DELGMB +2 # -DELGMBZ
CA -DELGMB +1
EXTEND
MP COSCDUZ # YIELDS -DELATTYPRIME/2 UNLIMITED
TS L
INDEX NDXCDUW
CA DAY/2MAX
TC LIMITSUB
EXTEND
DV COSCDUZ
XCH -DELGMB +1 # -DELGMBY, FETCHING UNLIMITED VALUE
EXTEND
MP SINCDUZ
DDOUBL
COM
EXTEND # YIELDS +DELATTX UNLIMITD, MAG < 180 DEG.
MSU -DELGMB # BASED ON UNLIMITED DELGMBV.
TS L # ONE BIT ERROR IF OPERANDS IN MSU
INDEX NDXCDUW # OF MIXED SIGNS. WHO CARES?
CA DAXMAX
TC LIMITSUB
TS -DELGMB # SAVE LIMITED +DELATTX
CCS FLAGOODW
CS -DELGMB # FETCH IT BACK CHGING SIGN IF WINDOW GOOD
TS -DELGMB # OTHERWISE USE ZERO FOR -DELATTX
CS -DELGMB +1
EXTEND
MP SINCDUZ
DDOUBL # YIELDS -CNTRIB TO -DELATTX FROM -DELGMBY
ADS -DELGMB # -DELGMBX. NO OVERFLOW SINCE LIMITED TO
# 20DEG(1+SIN(70DEG)/COS(70DEG)) < 180DEG
# Page 917
# COMPUTE COMMANDED ATTITUDE RATES
#
# [ OMEGAPD ] [ -2 -4 SINCDUZ +0 ] [ -DELGMBZ ]
# [ ] [ ] [ ]
# [ OMEGAQD ] = [ +0 -8 COSCDUZ COSCDUX -4 SINCDUX ] [ -DELGMBY ]
# [ ] [ ] [ ]
# [ OMEGARD ] [ +0 +8 COSCDUZ SINCDUX -4 COSCDUX ] [ -DELGMBZ ]
#
# ATTITUDE ANGLE RATES IN UNITS OF PI/4 RAD/SEC = K TRIG FCNS IN UNITS OF 2 X GIMBAL ANGLE RATES IN UNITS OF
# PI/2 RAD/SEC. THE CONSTANTS ARE BASED ON DELGMB BEING THE GIMBAL ANGLE CHANGES IN UNITS OF PI RADIANS,
# AND 2 SECONDS BEING THE COMPUTATION PERIOD (THE PERIOD BETWEEN SUCCESSIVE PASSES THRU FINDCDUW).
CS -DELGMB
TS OMEGAPD
CS -DELGMB +1
EXTEND
MP SINCDUZ
DDOUBL
ADS OMEGAPD
ADS OMEGAPD
CS -DELGMB +1
EXTEND
MP COSCDUX
DDOUBL
EXTEND
MP COSCDUZ
TS OMEGAQD
CS -DELGMB +2
EXTEND
MP SINCDUX
ADS OMEGAQD
ADS OMEGAQD
ADS OMEGAQD
CA -DELGMB +1
EXTEND
MP SINCDUX
DDOUBL
EXTEND
MP COSCDUZ
TS OMEGARD
CS -DELGMB +2
EXTEND
MP COSCDUX
ADS OMEGARD
ADS OMEGARD
ADS OMEGARD
# Page 918
# FINAL TRANSFER
CA TWO
CDUWXFR TS TEM2
INDEX TEM2
CA -DELGMB
EXTEND
MP DT/DELT # RATIO OF DAP INTERVAL TO CDUW INTERVAL
TC ONESTO2S
INDEX TEM2
TS DELCDUX # ANGLE INTERFACE
INDEX TEM2
CCS OMEGAPD
AD ONE
TCF +2
AD ONE
EXTEND # WE NOW HAVE ABS(OMEGAPD,QD,RD)
INDEX TEM2
MP OMEGAPD
EXTEND
MP BIT11 # 1/16
EXTEND
INDEX TEM2 # 2
DV 1JACC # UNITS PI/4 RAD/SEC
TS L
CA DELERLIM
TC LIMITSUB
INDEX TEM2
TS DELPEROR # LAG ANGLE = OMEGA ABS(OMEGA)/2 ACCEL
CCS TEM2
TCF CDUWXFR
# HAUSKEEPING AND RETURN
TCQCDUW CA ECDUWUSR
TS EBANK # RETURN USER'S EBANK
TC INTPRET
SETPD GOTO
0
QCDUWUSR # NORMAL AND ABNORMAL RETURN TO USER
# Page 919
# THRUST VECTOR FILTER SUBROUTINE
FLTRSUB EXTEND
QXCH TEM2
TS TEM3 # SAVE ORIGINAL OFFSET
COM # ONE MCT, NO WDS, CAN BE SAVED IF NEG OF
AD L # ORIG OFFSET ARRIVES IN A, BUT IT'S
EXTEND # NOT WORTH THE INCREASED OBSCURITY.
INDEX NDXCDUW
MP GAINFLTR
TS L # INCR TO OFFSET, UNLIMITED
CA DUNFVLIM # SAME LIMIT FOR Y AND Z
TC LIMITSUB # YIELDS INCR TO OFFSET, LIMITED
AD TEM3 # ORIGINAL OFFSET
TS L # TOTAL OFFSET, UNLIMITED
CA UNFVLIM # SAME LIMIT FOR Y AND Z
TC LIMITSUB # YIELDS TOTAL OFFSET, LIMITED
TC TEM2
# SUBR TO TEST THE ANGLE BETWEEN THE PROPOSED WINDOW AND THRUST CMD VCTS
UNWCTEST DOT DSQ
UNX/2
DSU BMN
DOTSWFMX
DCMCL
SSP RVQ # RVQ FOR ALT CHOICE IF DOT MAGN TOO LARGE
FLAGOODW # ZEROING WINDOW GOOD FLAG
0
# Page 920
# NB2CDUSP RETURNS THE 2'S COMPLEMENT, PI, SP CDU ANGLES X,Y,Z IN MPAC,+1,+2 GIVEN THE MATRIX WHOSE ROW VECTORS
# ARE THE SEMI-UNIT NAV BASE VECTORS X,Y,X EXPRESSED IN STABLE MEMBER COORDINATES, LOCATED AT 0 IN THE PUSH LIST.
# NB2CDUSP USES THE ARCTRGSP WHICH HAS A MAXIMUM ERROR OF +-4 BITS.
NB2CDUSP DLOAD DSQ
2
BDSU BPL
DP1/4TH
+3
DLOAD
ZEROVECS # IN CASE SIN WAS SLIGHTLY > 1/2
SQRT EXIT # YIELDS COS(CDUZ) IN UNITS OF 2
EXTEND
DCA MPAC
DDOUBL
TS TEM5
TCF +3
CA POSMAX # OVERFLOW. FETCH POSMAX, MPAC ALWAYS POS
TS TEM5 # COS(CDUZ) IN TEM5, UNITS 1
INDEX FIXLOC
CA 2
LXCH MPAC
TC ARCTRGSP
TS MPAC +2 # CDUZ
CA ZERO
TC DVBYCOSM
CA FOUR
TC DVBYCOSM
CS TEM1
TC ARCTRGSP
TS MPAC +1 # CDUY
CA BIT4
TC DVBYCOSM
CA 16OCT
TC DVBYCOSM
CS TEM1
TC ARCTRGSP
TS MPAC # CDUX
TC INTPRET
RVQ
16OCT OCT 16
# Page 921
# THE ELEMENTS OF THE NAV BASE MATRIX WHICH WE MUST DIVIDE BY COS(MGA)
# ALREADY CONTAIN COS(MGA)/2 AS A FACTOR. THEREFORE THE QUOTIENT SHOULD
# ORDINARILY NEVER EXCEED 1/2 IN MAGNITUDE. BUT IF THE MGA IS NEAR PI/2
# THEN COS(MGA) IS NEAR ZERO, AND THERE MAY BE SOME CHAFF IN THE OTHER
# ELEMENTS OF THE MATRIX WHICH WOULD PRODUCE CHAOS UNDER DIVISION.
# BEFORE DIVIDING WE MAKE SURE COS(MGA) IS AT LEAST ONE BIT LARGER
# THAN THE MAGNITUDE OF THE HIGH ORDER PART OF THE OPERAND.
#
# IF ONE OR MORE DIVIDES CANNOT BE PERFORMED, THIS MEANS THAT THE
# REQUIRED MGA IS VERY NEARLY +-PI/2 AND THEREFORE THE OTHER GIMBAL
# ANGLES ARE INDETERMINATE. THE INNER AND OUTER GIMBAL ANGLES RETURNED
# IN THIS CASE WILL BE RANDOM MULTIPLES OF PI/2.
DVBYCOSM AD FIXLOC
TS ADDRWD # ADRES OF OPERAND
INDEX ADDRWD # FETCH NEG ABS OF OPERAND, AD TEM5, AND
CA 0 # SKIP DIVIDE IF RESULT NEG OR ZERO
EXTEND
BZMF +2
COM
AD TEM5 # C(A) ZERO OR NEG, C(TEM5) ZERO OR POS
EXTEND
BZMF TSL&TCQ # DIFFERENCE ALWAYS SMALL IF BRANCH
EXTEND # TEM5 EXCEEDS ABS HIGH ORDER PART OF
INDEX ADDRWD # OPERAND BY AT LEAST ONE BIT.
DCA 0 # THEREFORE IT EXCEEDS THE DP OPERAND
EXTEND # AND DIVISION WILL ALWAYS SUCCEED.
DV TEM5
TSL&TCQ TS L
LXCH TEM1
TC Q
# Page 922
# ARCTRGSP RETURNS THE 2'S COMPLEMENT, PI, SP ANGLE IN THE A REGISTER GIVEN ITS SINE IN A AND ITS COSINE IN L IN
# UNITS OF 2. THE RESULT IS AN UNAMBIGUOUS ANGLE ANYWHERE IN THE CIRCLE, WITH A MAXIMUM ERROR OF +-4 BITS.
# THE ERROR IS PRODUCED BY THE SUBROUTINE SPARCSIN WHICH IS USED ONLY IN THE REGION +-45 DEGREES.
ARCTRGSP EXTEND
BZF SINZERO # TO AVOID DIVIDING BY ZERO
EXTEND
QXCH TEM4
TS TEM2
CA L
TS TEM3
CA ZERO
EXTEND
DV TEM2
EXTEND
BZF USECOS
CCS TEM3 # SIN IS SMALLER OR EQUAL
CA ZERO
TCF +4
CS TEM2 # IF COS NEG, REVERSE SIGN OF SIN,
TS TEM2 # ANGLE = PI-ARCSIN(SIN)
CA NEGMAX # PICK UP PI, 2'S COMPLEMENT
TS TEM3 # WE NO LONGER NEED COS
CA TEM2
TC SPARCSIN -1
TC ONESTO2S
EXTEND
MSU TEM3
1TO2&TCQ TC ONESTO2S
TC TEM4
USECOS CS TEM3 # COS IS SMALLER
TC SPARCSIN -1 # ANGLE = SIGN(SIN)(FI/2-ARCSIN(COS))
AD HALF
TS TEM3 # WE NO LONGER NEED COS
CCS TEM2
CA TEM3
TCF 1TO2&TCQ
CS TEM3
TCF 1TO2&TCQ
SINZERO CCS L
CA ZERO
TC Q
CA NEGMAX # PI, 2'S COMP
TC Q
# Page 923
# SPARCSIN TAKES AN ARGUMENT SCALED UNITY IN A AND RETURNS AN ANGLE SCALED
# 180 DEGREES IN A. IT HAS BEEN UNIT TESTED IN THE REGION +-.94 (+-70
# DEGREES) AND THE MAXIMUM ERROR IS +-5 BITS WITH AN AVERAGE TIME OF
# 450 MICROSECONDS. SPARCSIN -1 TAKES THE ARGUMENT SCALED TWO. (BOB CRISP)
DOUBLE
SPARCSIN TS SR
TCF +4
INDEX A
CS LIMITS
TS SR
EXTEND
MP A
TS TEM1
EXTEND
MP DPL9
AD DPL7
EXTEND
MP TEM1
AD DPL5
EXTEND
MP TEM1
AD DPL3
EXTEND
MP TEM1
AD DPL1
EXTEND
MP SR
TC Q
DPL1 DEC 10502
DPL3 DEC 432
DPL5 DEC 7300
DPL7 DEC -11803
DPL9 DEC 8397
# Page 924
# LIMITSUB LIMITS THE MAGNITUDE OF THE POSITIVE OR NEGATIVE VARIABLE
# ARRIVING IN L TO THE POSITIVE LIMIT ARRIVING IN A.
# THE SIGNED LIMITED VARIABLE IS RETURNED IN A.
#
# VERSION COUTESY HUGH BLAIR-SMITH
LIMITSUB TS TEM1
CA ZERO
EXTEND
DV TEM1
CCS A
LXCH TEM1
TCF +2
TCF +3
CA L
TC Q
CS TEM1
TC Q
# SUBROUTINE TO CONVERT 1'S COMP SP TO 2'S COMP
ONESTO2S CCS A
AD ONE
TC Q
CS A
TC Q
# NO ATTITUDE CONTROL
NOATTCNT TC ALARM
OCT 00402 # NO ATTITUDE CONTROL
+2 INHINT # COME HERE FOR NOATTCNT WITHOUT ALARM
TC IBNKCALL # RELINT AT TC INTPRET AFTER TCQCDUW
FCADR STOPRATE
TCF TCQCDUW # RETURN TO USER SKIPPING AUTOPILOT CMDS
# MIDDLE GIMBAL ANGLE ALARM
ALARMMGA TC ALARM
OCT 00401
TCF MGARET
# Page 925
#******************************************************************
# CONSTANTS
#******************************************************************
# ADDRESS CONSTANTS
ECDUWL ECADR ECDUW
# THRUST DIRECTION FILTER CONSTANTS
GAINFLTR DEC .2 # GAIN FILTER SANS CSM
DEC .1 # GAIN FILTER WITH CSM
DUNFVLIM DEC .007 B-1 # 7 MR MAX CHG IN F DIR IN VEH IN 2 SECS.
# THIS DOES NOT ALLOW FOR S/C ROT RATE.
UNFVLIM DEC .129 B-1 # 129 MR MAX THRUST OFFSET. 105 MR TRAVEL
# +10MR DEFL+5MR MECH MOUNT+9MR ABLATION.
# CONSTANT RELATED TO GIMBAL ANGLE COMPUTATIONS
DOTSWFMX DEC .93302 B-4 # LIM COLNRTY OF UNWC/2 & UNFC/2 TO 85 DEG
# LOWER PART COMES FROM NEXT CONSTANT
DAXMAX DEC .11111111111 # DELATTX LIM TO 20 DEG IN 2 SECS, 1'S, PI
DEC .0111111111 # 2 DEG WHEN CSM DOCKED
DAY/2MAX DEC .05555555555 # LIKEWISE FOR DELATTY
DEC .0055555555
DAZMAX = DAXMAX # LIKEWISE FOR DELATTZ
CDUZDLIM DEC .3888888888 # 70 DEG LIMIT FOR MGA, 1'S, PI
# CONSTANTS FOR DATA TRANSFER
DT/DELT DEC .05 # .1 SEC/2 SEC WHICH IS THE AUTOPILOT
# CONTROL SAMPLE PERIOD/COMPUTATION PERIOD
DELERLIM = DAY/2MAX # 0 DEG LIMIT FOR LAG ANGLES, 1'S, PI
# *** END OF FLY .132 ***
