RTB_OP_CODES.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: RTB_OP_CODES.agc
## Purpose: A section of Luminary revision 116.
## It is part of the source code for the Lunar Module's (LM)
## Apollo Guidance Computer (AGC) for Apollo 12.
## This file is intended to be a faithful transcription, except
## that the code format has been changed to conform to the
## requirements of the yaYUL assembler rather than the
## original YUL assembler.
## Reference: pp. 1387-1392
## Assembler: yaYUL
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 2017-01-22 MAS Created from Luminary 99.
## 2017-02-09 RRB Updated for Luminary 116.
## 2017-03-14 RSB Proofed comment text via 3-way diff vs
## Luminary 99 and 131 ... no problems found.
## Page 1387
BANK 22
SETLOC RTBCODES
BANK
EBANK= XNB
COUNT* $$/RTB
# LOAD TIME2, TIME1 INTO MPAC:
LOADTIME EXTEND
DCA TIME2
TCF SLOAD2
# CONVERT THE SINGLE PRECISION 2'S COMPLEMENT NUMBER ARRIVING IN MPAC (SCALED IN HALF-REVOLUTIONS) TO A
# DP 1'S COMPLEMENT NUMBER SCALED IN REVOLUTIONS.
CDULOGIC CCS MPAC
CAF ZERO
TCF +3
NOOP
CS HALF
TS MPAC +1
CAF ZERO
XCH MPAC
EXTEND
MP HALF
DAS MPAC
TCF DANZIG # MODE IS ALREADY AT DOUBLE-PRECISION
# FORCE TP SIGN AGREEMENT IN MPAC:
SGNAGREE TC TPAGREE
TCF DANZIG
# CONVERT THE DP 1'S COMPLEMENT ANGLE SCALED IN REVOLUTIONS TO A SINGLE PRECISION 2'S COMPLEMENT ANGLE
# SCALED IN HALF-REVOLUTIONS.
1STO2S TC 1TO2SUB
CAF ZERO
TS MPAC +1
TCF NEWMODE
# DO 1STO2S ON A VECTOR OF ANGLES:
V1STO2S TC 1TO2SUB # ANSWER ARRIVES IN A AND MPAC.
DXCH MPAC +5
DXCH MPAC
TC 1TO2SUB
## Page 1388
TS MPAC +2
DXCH MPAC +3
DXCH MPAC
TC 1TO2SUB
TS MPAC +1
CA MPAC +5
TS MPAC
TPMODE CAF ONE # MODE IS TP.
TCF NEWMODE
# V1STO2S FOR 2 COMPONENT VECTOR. USED BY RR.
2V1STO2S TC 1TO2SUB
DXCH MPAC +3
DXCH MPAC
TC 1TO2SUB
TS L
CA MPAC +3
TCF SLOAD2
# SUBROUTINE TO DO DOUBLING AND 1'S TO 2'S CONVERSION:
1TO2SUB DXCH MPAC # FINAL MPAC +1 UNSPECIFIED.
DDOUBL
CCS A
AD ONE
TCF +2
COM # THIS WAS REVERSE OF MSU.
TS MPAC # AND SKIP ON OVERFLOW.
TC Q
INDEX A # OVERFLOW UNCORRECT AND IN MSU.
CAF LIMITS
ADS MPAC
TC Q
# THE FOLLOWING ROUTINE INCREMENTS IN 2S COMPLEMENT THE REGISTER WHOSE ADDRESS IS IN BUF BY THE 1S COMPL.
# QUANTITY FOUND IN TEM2. THIS MAY BE USED TO INCREMENT DESIRED IMU AND OPTICS CDU ANGLES OR ANY OTHER 2S COMPL.
# (+0 UNEQUAL TO -0) QUANTITY. MAY BE CALLED BY BANKCALL/SWCALL.
CDUINC TS TEM2 # 1S COMPL.QUANT. ARRIVES IN ACC. STORE IT
INDEX BUF
CCS 0 # CHANGE 2S COMPL. ANGLE(IN BUF)INTO 1S
AD ONE
TCF +4
AD ONE
## Page 1389
AD ONE # OVERFLOW HERE IF 2S COMPL. IS 180 DEG.
COM
AD TEM2 # SULT MOVES FROM 2ND TO 3D QUAD. (OR BACK)
CCS A # BACK TO 2S COMPL.
AD ONE
TCF +2
COM
TS TEM2 # STORE 14BIT QUANTITY WITH PRESENT SIGN
TCF +4
INDEX A # SIGN.
CAF LIMITS # FIX IT, BY ADDING IN 37777 OR 40000
AD TEM2
INDEX BUF
TS 0 # STORE NEW ANGLE IN 2S COMPLEMENT.
TC Q
## Page 1390
# RTB TO TORQUE GYROS, EXCEPT FOR THE CALL TO IMUSTALL. ECADR OF COMMANDS ARRIVES IN X1.
PULSEIMU INDEX FIXLOC # ADDRESS OF GYRO COMMANDS SHOULD BE IN X1
CA X1
TC BANKCALL
CADR IMUPULSE
TCF DANZIG
## Page 1391
# THE SUBROUTINE SIGNMPAC SETS C(MPAC, MPAC +1) TO SIGN(MPAC).
# FOR THIS, ONLY THE CONTENTS OF MPAC ARE EXAMINED. ALSO +0 YIELDS POSMAX AND -0 YIELDS NEGMAX.
# ENTRY MAY BE BY EITHER OF THE FOLLOWING:
# 1. LIMIT THE SIZE OF MPAC ON INTERPRETIVE OVERFLOW:
# ENTRY: BOVB
# SIGNMPAC
# 2. GENERATE IN MPAC THE SIGNUM FUNCTION OF MPAC:
# ENTRY: RTB
# SIGNMPAC
# IN EITHER CASE, RETURN IS TO THE NEXT INTERPRETIVE INSTRUCTION IN THE CALLING SEQUENCE.
SIGNMPAC EXTEND
DCA DPOSMAX
DXCH MPAC
CCS A
DPMODE CAF ZERO # SETS MPAC +2 TO ZERO IN THE PROCESS
TCF SLOAD2 +2
TCF +1
EXTEND
DCS DPOSMAX
TCF SLOAD2
# RTB OP CODE NORMUNIT IS LIKE INTERPRETIVE INSTRUCTION UNIT, EXCEPT THAT IT CAN BE DEPENDED ON NOT TO BLOW
# UP WHEN THE VECTOR BEING UNITIZED IS VERY SMALL -- IT WILL BLOW UP WHEN ALL COMPONENTS ARE ZERO. IF NORMUNIT
# IS USED AND THE UPPER ORDER HALVES OF ALL COMPONENTS ARE ZERO, THE MAGNITUDE RETURNED IN 36D WILL BE TOO LARGE
# BY A FACTOR OF 2(13) AND THE SQUARED MAGNITUDE RETURNED AT 34D WILL BE TOO BIG BY A FACTOR OF 2(26).
NORMUNX1 CAF ONE
TCF NORMUNIT +1
NORMUNIT CAF ZERO
AD FIXLOC
TS MPAC +2
TC BANKCALL # GET SIGN AGREEMENT IN ALL COMPONENTS
CADR VECAGREE
CCS MPAC
TCF NOSHIFT
TCF +2
TCF NOSHIFT
CCS MPAC +3
TCF NOSHIFT
TCF +2
TCF NOSHIFT
CCS MPAC +5
TCF NOSHIFT
TCF +2
TCF NOSHIFT
## Page 1392
CA MPAC +1 # SHIFT ALL COMPONENTS LEFT 13
EXTEND
MP BIT14
DAS MPAC # DAS GAINS A LITTLE ACCURACY
CA MPAC +4
EXTEND
MP BIT14
DAS MPAC +3
CA MPAC +6
EXTEND
MP BIT14
DAS MPAC +5
CAF THIRTEEN
INDEX MPAC +2
TS 37D
OFFTUNIT TC POSTJUMP
CADR UNIT +1 # SKIP THE "TC VECAGREE" DONE AT UNIT
NOSHIFT CAF ZERO
TCF OFFTUNIT -2
# RTB VECSGNAG ... FORCES SIGN AGREEMENT OF VECTOR IN MPAC.
VECSGNAG TC BANKCALL
CADR VECAGREE
TC DANZIG
