### FILE="Main.annotation"
## Copyright:   Public domain.
## Filename:	RTB_OP_CODES.agc
## Purpose:     Part of the source code for Colossus build 237.
##              This is for the Command Module's (CM) Apollo Guidance
##              Computer (AGC), for Apollo 8.
## Assembler:   yaYUL
## Contact:     Jim Lawton <jim DOT lawton AT gmail DOT com>
## Website:     www.ibiblio.org/apollo/index.html
## Page Scans:  www.ibiblio.org/apollo/ScansForConversion/Colossus237/
## Mod history: 2011-04-17 JL	Adapted from corresponding Colossus 249 file.
##		2017-01-01 RSB	Proofed comment text using octopus/ProoferComments,
##				and fixed errors found.

## Page 1472
		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

#          READ THE PIPS INTO MPAC WITHOUT CHANGING THEM:

READPIPS	INHINT
		CA	PIPAX
		TS	MPAC
		CA	PIPAY
		TS	MPAC +3
		CA	PIPAZ
		RELINT
		TS	MPAC +5

		CAF	ZERO
		TS	MPAC +1
		TS	MPAC +4
		TS	MPAC +6

VECMODE		TCF	VMODE
#          FORCE TP SIGN AGREEMENT IN MPAC:

SGNAGREE	TC	TPAGREE
## Page 1473
		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
		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.
## Page 1474
		TC	Q

		INDEX	A		# OVERFLOW UNCORRECT AND IN MSU.
		CAF	LIMITS
		ADS	MPAC
		TC	Q

## Page 1475
#          SUBROUTINE TO INCREMENT CDUS
INCRCDUS	CAF	LOCTHETA
		TS	BUF		# PLACE ADRES(THETA) IN BUF.
		CAE	MPAC		# INCREMENT IN 1S COMPL.
		TC	CDUINC

		INCR	BUF
		CAE	MPAC +3
		TC	CDUINC

		INCR	BUF
		CAE	MPAC +5
		TC	CDUINC

		TCF	VECMODE

LOCTHETA	ADRES	THETAD

#          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
		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 1476
#          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 1477
# EACH ROUTINE TAKES A 3X3 MATRIX STORED IN DOUBLE PRECISION IN A FIXED AREA OF ERASABLE MEMORY AND REPLACES IT
# WITH THE TRANSPOSE MATRIX. TRANSP1 USES LOCATIONS XNB+0,+1 THROUGH XNB+16D, 17D AND TRANSP2 USES LOCATIONS
# XNB1+0,+1 THROUGH XNB1+16D, 17D. EACH MATRIX IS STORED BY ROWS.

XNBEB		ECADR	XNB
XNB1EB		ECADR	XNB1

		EBANK=	XNB

TRANSP1		CAF	XNBEB
		TS	EBANK
		DXCH	XNB +2
		DXCH	XNB +6
		DXCH	XNB +2

		DXCH	XNB +4
		DXCH	XNB +12D
		DXCH	XNB +4

		DXCH	XNB +10D
		DXCH	XNB +14D
		DXCH	XNB +10D
		TCF	DANZIG


		EBANK=	XNB1

TRANSP2		CAF	XNB1EB
		TS	EBANK
		DXCH	XNB1 +2
		DXCH	XNB1 +6
		DXCH	XNB1 +2

		DXCH	XNB1 +4
		DXCH	XNB1 +12D
		DXCH	XNB1 +4

		DXCH	XNB1 +10D
		DXCH	XNB1 +14D
		DXCH	XNB1 +10D
		TCF	DANZIG

## Page 1478
#          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 1479
		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