Pre-launch Review
TRIM GIMBAL CONTROL SYSTEM
Scanned pages: 1472-1485
# Copyright: Public domain.# Filename: TRIM_GIMBAL_CNTROL_SYSTEM.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: Ron Burkey <info@sandroid.org>.# Website: www.ibiblio.org/apollo.# Pages: 1472-1485# Mod history: 2009-05-27 RSB Adapted from the corresponding# Luminary131 file, using page# images from Luminary 1A.## 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 1472 BANK 21 EBANK= QDIFF SETLOC DAPS4 BANK
COUNT* $$/DAPGT
# CONTROL REACHES THIS POINT UNDER EITHER OF THE FOLLOWING TWO CONDITIONS ONCE THE DESCENT ENGINE AND THE DIGITAL# AUTOPILOT ARE BOTH ON:# A) THE TRIM GIMBAL CONTROL LAW WAS ON DURING THE PREVIOUS Q,R-AXIS TIME5 INTERRUPT (OR THE DAPIDLER# INITIALIZATION WAS SET FOR TRIM GIMBAL CONTROL AND THIS IS THE FIRST PASS), OR# B) THE Q,R-AXES RCS AUTOPILOT DETERMINED THAT THE VEHICLE WAS ENTERING (OR HAD JUST ENTERED) A COAST# ZONE WITH A SMALL OFFSET ANGULAR ACCELERATION.# GTS IS THE ENTRY TO THE GIMBAL TRIM SYSTEM FOR CONTROLLING ATTITUDE ERRORS AND RATES AS WELL AS ACCELERATIONS.
GTS CAF NEGONE # MAKE THE NEXT PASS THROUGH THE DAP BE TS COTROLER # THROUGH RCS CONTROL, CAF FOUR # AND ENSURE THAT IT IS NOT A SKIP. TS SKIPU TS SKIPV
CAF TWO TS INGTS # SET INDICATOR OF GTS CONTROL POSITIVE. TS QGIMTIMR # SET TIMERS TO 200 MSEC TO AVOID BOTH TS RGIMTIMR # RUNAWAY AND INTERFERENCE BY NULLING.
# THE DRIVE SETTING ALGORITHM## DEL = SGN(OMEGA + ALPHA*ABS(ALPHA)/(2*K))# 2 1/2 2 3/2# NEGUSUM = ERROR*K + ALPHA*(DEL*OMEGA + ALPHA /(3*K)) + DEL*K (DEL*OMEGA + ALPHA /(2*K))## DRIVE = -SGN(NEGUSUM)
CA SR # SAVE THE SR. SHIFT IT LEFT TO CORRECT AD A # FOR THE RIGHT SHIFT DUE TO EDITING. TS SAVESR
GTSGO+ON CAF TWO # SET INDEXER FOR R-AXIS CALCULATIONS. TCF GOQTRIMG +1
GOQTRIMG CAF ZERO # SET INDEXER FOR Q-AXIS CALCULATIONS TS QRCNTR# Page 1473# RSB 2009 -----------------------------------------------------------------------# Everything between this line and the similar line below was simply filled-in# as-is from Luminary 131, and then verified to assemble to the proper binary# values. This area is blank on the Luminary 099 print-out, as if the printer# ribbon had run out. INDEX QRCNTR # AOS SCALED AT PI/2 CA AOSQ EXTEND MP BIT2 # RESCALE AOS TO PI/4 EXTEND BZF GTSQAXIS -3 # USE FULL SCALE FOR LARGER AOS ESTIMATES.
INDEX A CS LIMITS # LIMITS +1 CONTAINS NEGMAX. XCH L # LIMITS -1 CONTAINS POSMAX.
CCS QRCNTR # PICK UP RATE FOR THIS AXIS. RATE CELLS INDEX A # USE ADJACENT, NOT SEPARATED. AT PI/4 CA EDOTQGTSQAXIS DXCH WCENTRAL
INDEX QRCNTR # COLLECT K FOR THIS AXIS CA KQ TS KCENTRAL
EXTEND # CONTROL AUTHORITY ZERO. AVOID DRIVING BZF POSDRIVE +1 # ENGINE BELL TO THE STOPS.
INDEX QRCNTR # QDIFF, RDIFF ARE STORED IN D.P. CAE QDIFF
ALGORTHM EXTEND # Q(R)DIFF IS THETA (ERROR) SCALED AT PI. MP KCENTRAL # FORM K*ERROR AT PI(2)/2(8), IN D.P. LXCH K2THETA EXTEND MP BIT5 # RESCALE TO 4*PI(2) DXCH K2THETA EXTEND MP BIT5 # FIRST TERM OF NEGUSUM IN K2THETA. ADS K2THETA +1 # NO CARRY NEEDED D.P. AT 4*PI(2)
CS ACENTRAL # FORM ALPHA(2)/(2*K) AT 16*PI, IN D.P., EXTEND # LIMITING QUOTIENT TO AVOID OVERFLOW. MP BIT14 # -ALPHA/2 IN A, SCALED AT PI/4 EXTEND MP ACENTRAL # -ALPHA(2)/2 IN A,L, SCALED AT PI(2)/16) AD KCENTRAL EXTEND BZMF HUGEQUOT # K-ALPHA(2)/2 SHOULD BE PNZ FO DIVISION
EXTEND DCS A # ALPHA(2)/2 - K AD KCENTRAL# RSB 2009 ----------------------------------------------------------------------- EXTEND DV KCENTRAL # HIGH ORDER OF QUOTIENT. XCH A2CNTRAL CA L # SHIFT UP THE REMAINDER. LXCH 7 # ZERO LOW-ORDER DIVIDEND. EXTEND# Page 1474 DV KCENTRAL XCH A2CNTRAL +1 # QUOTIENT STORED AT 16*PI , D.P. TCF HAVEQUOT
HUGEQUOT CA POSMAX TS L DXCH A2CNTRAL # LIMITED QUOTIENT STORED AT 16*PI, D.P.
HAVEQUOT CA WCENTRAL EXTEND MP BIT9 # RESCALE OMEGA AT 16*PI IN D.P. DXCH K2CNTRAL # LOWER WORD OVERLAYS OMEGA IN WCENTRAL
EXTEND DCA K2CNTRAL DXCH FUNCTION
CA ACENTRAL # GET ALPHA*ABS(ALPHA)/(2*K) EXTEND BZMF +4
EXTEND DCA A2CNTRAL TCF +3
EXTEND DCS A2CNTRAL
DAS FUNCTION # OMEGA + ALPHA*ABS(ALPHA)/(2*K) AT 16*PI
CCS FUNCTION # DEL = +1 FOR FUNCT1 GREATER THAN ZERO. TCF POSFNCT1 # OTHERWISE DEL = -1 TCF +2 TCF NEGFNCT1
CCS FUNCTION +1 # USE LOW ORDER WORD SINCE HIGH IS ZEROPOSFNCT1 CAF BIT1 TCF +2NEGFNCT1 CS BIT1 TS DEL
CCS DEL # REPLACE OMEGA BY DEL*OMEGA TCF FUNCT2 # POSITIVE DEL VALUE. PROCEED. TCF DEFUNCT TCF NEGFNCT2
DEFUNCT TS K2CNTRAL TS K2CNTRAL +1 TCF FUNCT2
# Page 1475NEG1/3 DEC -.33333
NEGFNCT2 EXTEND DCS K2CNTRAL DXCH K2CNTRAL
FUNCT2 EXTEND DCA A2CNTRAL DAS K2CNTRAL # DEL*OMEGA + ALPHA(2)/(2*K) AT 16*PI,D.P.
FUNCT3 CA A2CNTRAL EXTEND MP NEG1/3 DXCH A2CNTRAL CA L EXTEND MP NEG1/3 ADS A2CNTRAL +1 TS L TCF +2 # A2CNTRAL NOW CONTAINS -ALPHA(2)/(6*K), ADS A2CNTRAL # SCALED AT 16*PI, IN D.P.
EXTEND DCA K2CNTRAL # DEL*OMEGA + ALPHA(2)/(3*K) IN A2CNTRAL, DAS A2CNTRAL # SCALED AT 16*PI, D.P.
CA A2CNTRAL EXTEND MP ACENTRAL DAS K2THETA CA A2CNTRAL +1 EXTEND MP ACENTRAL # ACENTRAL MAY NOW BE OVERLAID. ADS K2THETA +1 TS L TCF +2 # TWO TERMS OF NEGUSUM ACCUMULATED, SO FAR ADS K2THETA # SCALED AT 4*PI(2), IN D.P.
GETROOT CA K2CNTRAL # K*(DEL*OMEGA + ALPHA(2)/(2*K)) IS THE EXTEND # TERM FOR WHICH A SQUARE ROOT IS NEEDED. MP KCENTRAL # K AT PI/2(8) DXCH FUNCTION CA K2CNTRAL +1 EXTEND MP KCENTRAL ADS FUNCTION +1 TS L TCF +2 ADS FUNCTION # DESIRED TERM IN FUNCTION, AT PI(2)/16# Page 1476 CCS DEL TCF RSTOFGTS TCF NEGUSUM TCF NEGATE TCF NEGUSUM
NEGATE EXTEND DCS K2CNTRAL DXCH K2CNTRAL TCF RSTOFGTS
BANK 16 EBANK= NEGUQ SETLOC DAPS1 BANK
# THE WRCHN12 SUBROUTINE SETS BITS 9,10,11,12 OF CHANNEL 12 ON THE BASIS OF THE CONTENTS OF NEGUQ,NEGUR WHICH ARE# THE NEGATIVES OF THE DESIRED ACCELERATION CHANGES. ACDT+C12 SETS Q(R)ACCDOT TO REFLECT THE NEW DRIVES.## WARNING: ACDT+C12 AND WRCHN12 MUST BE CALLED WITH INTERRUPT INHIBITED.
BGIM OCTAL 07400CHNL12 EQUALS ITEMP6ACDT+C12 CS NEGUQ EXTEND # GIMBAL DRIVE REQUESTS. MP ACCDOTQ LXCH QACCDOT CS NEGUR EXTEND MP ACCDOTR LXCH RACCDOT
CCS NEGUQ CAF BIT10 TCF +2 CAF BIT9 TS CHNL12
CCS NEGUR CAF BIT12 TCF +2 CAF BIT11 ADS CHNL12 # (STORED RESULT NOT USED AT PRESENT)
CS BGIM EXTEND RAND CHAN12 AD CHNL12 EXTEND WRITE CHAN12# Page 1477 CS CALLGMBL # TURN OFF REQUEST FOR ACDT+C12 EXECUTION. MASK RCSFLAGS TS RCSFLAGS
TC Q # RETURN TO CALLER.
BANK 21 EBANK= QDIFF SETLOC DAPS4 BANK
# Page 1478# SUBROUTINE TIMEGMBL: MOD 0, OCTOBER 1967, CRAIG WORK## TIMEGMBL COMPUTES THE DRIVE TIME NEEDED FOR THE TRIM GIMBAL TO POSITION THE DESCENT ENGINE NOZZLE SO AS TO NULL# THE OFFSET ANGULAR ACCELERATION ABOUT THE Q (OR R) AXIS. INSTEAD OF USING AOSQ(R), TIMEGMBL USES .4*AOSQ(R),# SCALED AT PI/8. FOR EACH AXIS, THE DRIVE TIME IS COMPUTED AS ABS(ALPHA/ACCDOT). A ZERO# ALPHA OR ACCDOT OR A ZERO QUOTIENT TURNS OFF THE GIMBAL DRIVE IMMEDIATELY. OTHERWISE, THE GIMBAL IS TURNED ON# DRIVING IN THE CORRECT DIRECTION. THE Q(R)GIMTIMR IS SET TO TERMINATE THE DRIVE AND Q(R)ACCDOT# IS STORED TO REFLECT THE NEW ACCELERATION DERIVATIVE. NEGUQ(R) WILL CONTAIN +1,+0,-1 FOR A Q(R)ACCDOT VALUE# WHICH IS NEGATIVE, ZERO, OR POSITIVE.## INPUTS: AOSQ,AOSR, SCALED AT P1/2, AND ACCDOTQ, ACCDOTR AT PI/2(7). PI/2(7).## OUTPUTS: NEW GIMBAL DRIVE BITS IN CHANNEL 12,NEGUQ,NEGUR,QACCDOT AND RACCDOT, THE LAST SCALED AT PI/2(7).# Q(R)GIMTIMR WILL BE SET TO TIME AND TERMINATE GIMBAL DRIVE(S)## DEBRIS: A,L,Q, ITEMPS 2,3,6, RUPTREG2 AND ACDT+C12 DEBRIS.## EXITS: VIA TC Q.## ALARMS, ABORTS, : NONE## SUBROUTINES: ACDT+C12, IBNKCALL## WARNING: THIS SUBROUTINE WRITES INTO CHANNEL 12 AND USES THE ITEMPS. THEREFORE IT MAY ONLY BE CALLED WITH# INTERRUPT INHIBITED.## ERASABLE STORAGE CONFIGURATION (NEEDED BY THE INDEXING METHODS):# NEGUQ ERASE +2 # NEGATIVE OF Q-AXIS GIMBAL DRIVE# (SPWORD) EQUALS NEGUQ +1 # ANY S.P. ERASABLE NUMBER, NOW THRSTCMD# NEGUR EQUALS NEGUQ +2 # NEGATIVE OF R-AXIS GIMBAL DRIVE# ACCDOTQ ERASE +2 # Q-JERK TERM SCALED AT PI/2(7) RAD/SEC(3)# (SPWORD) EQUALS ACCDOTQ +1 # ANY S.P. ERASABLE NUMBER NOW QACCDOT# ACCDOTR EQUALS ACCDOTQ +2 # R-JERK TERM SCALED AT PI/2(7) RAD/SEC(3)# # ACCDOTQ,ACCDOTR ARE MAGNITUDES.# AOSQ ERASE +4 # Q-AXIS ACC., D.P. AT PI/2 R/SEC(2)# AOSR EQUALS AOSQ +2 # R-AXIS ACCELERATION SCALED AT PI/2 R/S2
QRNDXER EQUALS ITEMP6OCT23146 OCTAL 23146 # DECIMAL .6NZACCDOT EQUALS ITEMP3
TIMEGMBL CAF ONE # INITIALZE ALLOWGTS. TS ALLOWGTS
CAF TWO # SET UP LOOP FOR R AXIS. LXCH Q # SAVE RETURN ADDRESS. LXCH RUPTREG2# Page 1479 TCF +2TIMQGMBL CAF ZERO # NOW DO THE Q-AXIS TS QRNDXER INDEX QRNDXER CA ACCDOTQ # ACCDOT IS PRESUMED TO BE AT PI/2(7). EXTEND BZMF TGOFFNOW # IS ACCDOT LESS THAN OR EQUAL TO 0? TS NZACCDOT # NO. STORE NON-ZERO, POSITIVE ACCDOT.
ALPHATRY INDEX QRNDXER CS AOSQ EXTEND BZF TGOFFNOW # IS ALPHA ZERO?
TS Q # SAVE A COPY OF -AOS. EXTEND # NO. RESCALE FOR TIMEGMBL USE. MP OCT23146 # OCTAL 23146 IS DECIMAL .6 AD Q # -1.6*AOS AT PI/2 = -.4*AOS AT PI/8. TS L # WAS THERE OVERFLOW? TCF SETNEGU # NO. COMPUTE DRIVE TIME.
CS A # RECOVER -SGN(AOS) IN THE A REGISTER. INDEX QRNDXER # YES. START DRIVE WITHOUT WAITLIST. XCH NEGUQ TCF NOTALLOW # KNOCK DOWN THE ALLOWGTS FLAG.
SETNEGU EXTEND BZMF POSALPH
COM TS ITEMP2 # STORE -ABS(.4*AOS) SCALED AT PI/8. CS BIT1 TCF POSALPH +2POSALPH TS ITEMP2 # STORE -ABS(.4*AOS) SCALED AT PI/8. CA BIT1 +2 INDEX QRNDXER # SGN(AOS) INTO NEGU TS NEGUQ # STORE SGN(ALPHA) AS NEGU
CA NZACCDOT EXTEND MP BIT12 # 2*ACCDOT, SCALED AT PI/8. AD ITEMP2 # -ABS(ALPHS) + 2*ACCDOT, AT PI/8. EXTEND BZMF NOTALLOW # IS DRIVE TIME MORE THAN TWO SECONDS? CS ITEMP2 # NO. COMPUTE DRIVE TIME. EXTEND # ABS(ALPHA) AT PI/8. MP OCT00240 # DECIMAL 10/1024 EXTEND # QUOTIENT IS DRIVE TIME AT WAITLIST. DV NZACCDOT # ABS(ALPHA)/ACCDOT AT 2(14)/100# Page 1480 EXTEND BZF TGOFFNOW # DRIVE TIME MUST BE GREATER THAN ZERO.
TCF DRIVEON
TGOFFNOW CAF ZERO # TURN OFF GIMBAL NOW. INDEX QRNDXER TS NEGUQ
TCF DONEYET
NOTALLOW CAF OCT31 INDEX QRNDXER TS QGIMTIMR CAF ZERO # DRIVE TIME IS MORE THAN 2 SECONDS, SO TS ALLOWGTS # DO NOT PERMIT FURTHER GTS ATTITUDE-RATE # CONTROL UNTIL AOSTASK APPROVES. TCF DONEYET # NO WAITLIST CALL IS MADE.
DRIVEON INDEX QRNDXER TS QGIMTIMR # CHOOSE Q OR R AXIS.
DONEYET CCS QRNDXER TCF TIMQGMBL
DXCH RUPTREG3 # PROTECT IBNKCALL ERASABLES. ACDT+C12 DXCH ITEMP2 # LEAVES ITEMPS2,3 ALONE.
TC IBNKCALL # TURN OFF CHANNEL BITS, SET Q(R)ACCDOTS. CADR ACDT+C12
DXCH ITEMP2 # RESTORE ERASABLES FOR IBNKCALL. DXCH RUPTREG3
TC RUPTREG2 # RETURN TO CALLER.
OCT00240 OCTAL 00240 # DECIMAL 10/1024
# Page 1481# THE FOLLOWING SECTION IS A CONTINUATION OF THE TRIM GIMBAL CONTROL FROM THE LAST GTS ENTRY. THE QUANTITY NEGUSUM# IS COMPUTED FOR EACH AXIS (Q,R), .707*DEL*FUNCTION(3/2) + K2THETA = NEGUSUM. NEW DRIVES ARE ENTERED TO CH 12.## THE SUBROUTINE GTSQRT ACCEPTS A DOUBLE PRECISION VALUE IN FUNCTION, FUNCTION +1 AND RETURNS A SINGLE-PRECISION# SQUARE ROOT OF THE FOURTEEN MOST SIGNIFICANT BITS OF THE ARGUMENT. ALSO, THE CELL SHFTFLAG CONTAINS A BINARY# EXPONENT S, SUCH THAT THE SQUARE ROOT (RETURNED IN THE A REGISTER) MUST BE SHIFTED RIGHT (MULTIPLIED BY 2 TO THE# POWER (-S)) IN ORDER TO BE THE TRUE SQUARE ROOT OF THE FOURTEEN MOST SIGNIFICANT BITS OF FUNCTION, FUNCTION +1.# SQUARE ROOT ERROR IS NOT MORE THAN 2 IN THE 14TH SIGNIFICANT BIT. CELLS CLOBBERED ARE A,L,SHFTFLAG,ININDEX,# HALFARG,SCRATCH,SR,FUNCTION, FUNCTION +1. GTSQRT IS CALLED BY TC GTSQRT AND RETURNS VIA TC Q OR TC FUNCTION +1.# ZERO OR NEGATIVE ARGUMENTS YIELD ZERO FOR SQUARE ROOTS.
GTSQRT CCS FUNCTION TCF GOODARG # FUNCTION IS POSITIVE. TAKE SQUARE ROOT. TCF +2 # HIGH ORDER WORD IS ZERO. TRY THE LOWER. TCF ZEROOT # NEGATIVE. USE ZERO FOR 1/2 POWER.
CA FUNCTION +1 EXTEND BZMF ZEROOT
TCF ZEROHIGH # PROCEED.ZEROOT CA ZERO TS SHFTFLAG TC Q
ZEROHIGH XCH FUNCTION # 14 MOST SIGNIFICANT BITS ARE IN THE XCH FUNCTION +1 # LOWER WORD. EXCHANGE THEM. CA SEVEN TCF GOODARG +1
GOODARG CA ZERO TS SHFTFLAG CA TWELVE # INITIALIZE THE SCALING LOOP. TS ININDEX TCF SCALLOOP
SCALSTRT CA FUNCTION TCF SCALDONE
MULBUSH CA NEG2 # IF ARG IS NOT LESS THAN 1/4, INDEX IS ADS ININDEX # ZERO, INDICATING NO SHIFT NEEDED. EXTEND # BRANCH IF ARG IS NOT LESS THAN 1/4. BZMF SCALSTRT # OTHERWISE COMPARE ARG WITH A REFERENCE # WHICH IS 4 TIMES LARGER THAN THE LAST.SCALLOOP CS FUNCTION INDEX ININDEX AD BIT15 # REFERENCE MAGNITUDE LESS OR EQUAL TO 1/4 EXTEND BZMF MULBUSH # IF ARG IS NOT LESS THAN REFERENCE, GO # AROUND THE MULBERRY BUSH ONCE MORE.# Page 1482 INDEX ININDEX CA BIT15 # THIS IS THE SCALE MAGNITUDE XCH HALFARG # 2**(-ININDEX) IS THE SHIFT DIVISOR. EXTEND # RESCALE ARGUMENT. DCA FUNCTION EXTEND DV HALFARG # ININDEX AND SHFTFLAG PRESERVE INFO FOR # RESCALING AFTER ROOT PROCESS.SCALDONE EXTEND QXCH FUNCTION +1 # SAVE Q FOR RETURN EXTEND MP BIT14 TS HALFARG MASK BIT13 CCS A CA OCT11276 AD ROOTHALF # INITIAL GUESS IS ROOT 1/2 OR POSMAX TC ROOTCYCL TC ROOTCYCL TC ROOTCYCL TC FUNCTION +1# ****************************************************************************************************************
RSTOFGTS TC GTSQRTPRODUCT XCH K2CNTRAL EXTEND MP K2CNTRAL DXCH K2CNTRAL EXTEND # THE PRODUCT OF MP L # 1/2 2 1/2 ADS K2CNTRAL +1 # K *(DEL*OMEGA + ALPHA /(2*K)) TS L # AND TCF +2 # 2 ADS K2CNTRAL # DEL*(DEL*OMEGA + ALPHA /(2*K)) NOW IN # K2CNTRAL
DOSHIFT CA ININDEX EXTEND # MULTIPLY IN THE FACTOR 2(-S), RETURNED MP BIT14 # BY THE GTSQRT SUBROUTINE ADS SHFTFLAG EXTEND BZF ADDITIN INDEX SHFTFLAG CA BIT15# Page 1483 XCH K2CNTRAL EXTEND MP K2CNTRAL DAS K2THETA XCH K2CNTRAL EXTEND MP K2CNTRAL +1 ADS K2THETA +1 TS L TCF +2 ADS K2THETA
TCF NEGUSUM
ADDITIN EXTEND DCA K2CNTRAL DAS K2THETA # NOW ADD IN THE K2THETA TERM.NEGUSUM CCS K2THETA # TEST SIGN OF HIGH ORDER PART. TCF NEGDRIVE TCF +2 TCF POSDRIVE
CCS K2THETA +1 # SIGN TEST FOR LOW ORDER PART.NEGDRIVE CA BIT1 TCF +2 # STOP GIMBAL DRIVE FOR A ZERO NEGUSUM.POSDRIVE CS BIT1 TS L # SAVE FOR DRIVE REVERSAL TEST. INDEX QRCNTR XCH NEGUQ
EXTEND MP L # MULTIPLY OLD NEGU AND NEW NEGU. CCS L TCF LOUPE # NON-ZERO GIMBAL DRIVE BEING CONTINUED.
TCF ZEROLOUP # NO REVERSAL PROBLEM HERE.
TCF REVERSAL # NON-ZERO GIMBAL DRIVE BEING REVERSED. TCF ZEROLOUP # NO REVERSAL PROBLEM HERE.
REVERSAL INDEX QRCNTR # A ZERO-DRIVE PAUSE IS NEEDED HERE. ZERO TS QACCDOT # IS IN A REGISTER FROM CCS ON (-1). INDEX QRCNTR CS GMBLBITA EXTEND WAND CHAN12
ZEROLOUP CS RCSFLAGS # SET UP REQUEST FOR ACDT+C12 CALL. MASK CALLGMBL ADS RCSFLAGS# Page 1484LOUPE CCS QRCNTR # HAVE BOTH AXES BEEN PROCESSED? TCF GOQTRIMG # NO. DO Q AXIS NEXT.
CA SAVESR # RESTORE THE SR TS SR
GOCLOSE EXTEND # TERMINATE THE JASK. DCA CLOSEADR DTCB
EBANK= AOSQCLOSEADR 2CADR CLOSEOUT # TERMINATE THE JASK.
TWELVE EQUALS OCT14ROOTHALF OCTAL 26501 # SQUARE ROOT OF 1/2GMBLBITA OCTAL 01400 # INDEXED WRT GMBLBITB DO NOT MOVE******OCT11276 OCTAL 11276 # POSMAX - ROOTHALFGMBLBITB OCTAL 06000 # INDEXED WRT GMBLBITA DO NOT MOVE******
# SUBROUTINE ROOTCYCL: BY CRAIG WORK,3 APRIL 68# ROOTCYCL IS A SUBROUTINE WHICH EXECUTES ONE NEWTON SQUARE ROOT ALGORITHM ITERATION. THE INITIAL GUESS AT THE# SQUARE ROOT IS PRESUMED TO BE IN THE A REGISTER AND ONE-HALF THE SQUARE IS TAKEN FROM HALFARG. THE NEW APPROXI-# MATION TO THE SQUARE ROOT IS RETURNED IN THE A REGISTER. DEBRIS: A,L,SR,SCRATCH. ROOTCYCL IS CALLED FROM# LOCATION (LOC) BY A TC ROOTCYCL, AND RETURNS (TC Q) TO LOC +1.# WARNING: IF THE INITIAL GUESS IS NOT GREATER THAN THE SQUARE, DIVIDE OR ADD OVERFLOW IS A REAL POSSIBILITY.
ROOTCYCL TS SCRATCH # STORE X TS SR # X/2 NOW IN SR CA HALFARG # ARG/2 IN THE A REG ZL # PREPARE FOR DIVISION EXTEND DV SCRATCH # (ARG/X)/2 AD SR # (X + ARG/X)/2 IN THE A REG TC Q