LANDING_ANALOG_DISPLAYS.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: LANDING_ANALOG_DISPLAYS.agc
## Purpose: A section of Luminary revision 173.
## It is part of the reconstructed source code for the second
## (unflown) release of the flight software for the Lunar
## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 14.
## The code has been recreated from a reconstructed copy of
## Luminary 178, as well as Luminary memo 167 (revision 1).
## It has been adapted such that the resulting bugger words
## exactly match those specified for Luminary 173 in NASA
## drawing 2021152N, which gives relatively high confidence
## that the reconstruction is correct.
## Reference: pp. 890-898
## Assembler: yaYUL
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 2019-09-18 MAS Created from Luminary 178.
## 2019-09-21 MAS Re-based on Luminary 131. Implemented ACB L-11
## by moving three checks as shown in the
## Luminary 173 flowcharts.
## 2021-05-30 ABS LADFWDV -> LATFWDV
## Page 891
BANK 21
SETLOC R10
BANK
EBANK= UNIT/R/
COUNT* $$/R10
LANDISP LXCH PIPCTR1 # UPDATE TBASE2 AND PIPCTR SIMULTANEOUSLY.
CS TIME1
DXCH TBASE2
CS FLAGWRD7 # IS LANDING ANALOG DISPLAYS FLAG SET?
MASK SWANDBIT
CCS A
TCF DISPRSET # NO.
CA IMODES33 # BIT 7 = 0 (DO ALTRATE), =1 (DO ALT.)
MASK BIT7
CCS A
TCF ALTOUT
ALTROUT TC DISINDAT # CHECK MODE SELECT SWITCH AND DIDFLG.
CS IMODES33
MASK BIT7
ADS IMODES33 # ALTERNATE ALTITUDE RATE WITH ALTITUDE.
CAF BIT2 # RATE COMMAND IS EXECUTED BEFORE RANGE.
EXTEND
WOR CHAN14 # ALTRATE (BIT2 = 1), ALTITUDE (BIT2 = 0).
ARCOMP CA RUNIT # COMPUTE ALTRATE = RUNIT.VVECT M/CS *2(-6).
EXTEND
MP VVECT # MULTIPLY X-COMPONENTS.
XCH RUPTREG1 # SAVE SINGLE PRECISION RESULT M/CS*2(-6).
CA RUNIT +1 # MULTIPLY Y-COMPONENTS.
EXTEND
MP VVECT +1
ADS RUPTREG1 # ACCUMULATE PARTIAL PRODUCTS.
CA RUNIT +2 # MULTIPLY Z-COMPONENTS.
EXTEND
MP VVECT +2
ADS RUPTREG1 # ALTITUDE RATE IN M/CS *2(-6).
CA ARCONV # CONVERT ALTRATE TO BIT UNITS (.5FPS/BIT)
EXTEND
MP RUPTREG1
DDOUBL
DDOUBL
XCH RUPTREG1 # ALTITUDE RATE IN BIT UNITS*2(-14).
CA DALTRATE # ALTITUDE RATE COMPENSATION FACTOR.
EXTEND
MP DT
AD RUPTREG1
TS ALTRATE # ALTITUDE RATE IN BIT UNITS*2(-14).
CS ALTRATE
## Page 892
EXTEND # CHECK POLARITY OF ALTITUDE RATE.
BZMF +2
TCF DATAOUT # NEGATIVE - SEND POS. PULSES TO ALTM REG.
CA ALTRATE # POSITIVE OR ZERO - SET SIGN BIT = 1 AND
AD BIT15 # SEND TO ALTM REGISTER. *DO NOT SEND +0*
DATAOUT TS ALTM # ACTIVATE THE LANDING ANALOG DISPLAYS - -
CAF BIT3
EXTEND
WOR CHAN14 # BIT3 DRIVES THE ALT/ALTRATE METER.
TCF TASKOVER # EXIT
ALTOUT TC DISINDAT # CHECK MODE SELECT SWITCH AND DIDFLG.
CS BIT7
MASK IMODES33
TS IMODES33 # ALTERNATE ALTITUDE RATE WITH ALTITUDE.
CS BIT2
EXTEND
WAND CHAN14
CCS ALTBITS # = -1 IF OLD ALT. DATA TO BE EXTRAPOLATED.
TCF +4
TCF +3
TCF OLDDATA
TS ALTBITS # SET ALTBITS FROM -0 TO +0.
CS ONE
DXCH ALTBITS # SET ALTBITS = -1 FOR SWITCH USE NEXT PASS.
DXCH ALTSAVE
CA BIT10 # NEW ALTITUDE EXTRAPOLATION WITH ALTRATE.
XCH Q
LXCH 7 # ZL
CA DT
EXTEND
DV Q # RESCALE DT*2(-14) TO *2(-9) TIME IN CS.
EXTEND
MP ARTOA2 # .0021322 *2(+8)
TCF OLDDATA +1 # RATE APPLIES FOR DT CS.
ZDATA2 DXCH ALTSAVE
TCF NEWDATA
OLDDATA CA ARTOA # RATE APPLIES FOR .5 SEC. (4X/SEC. CYCLE)
EXTEND
MP ALTRATE # EXTRAPOLATE WITH ALTITUDE RATE.
DDOUBL
AD ALTSAVE +1
TS ALTSAVE +1
CAF ZERO
ADS ALTSAVE
CAF POSMAX # FORCE SIGN AGREEMENT ASSUMING A
AD ONE # NON-NEGATIVE ALTSAVE.
AD ALTSAVE +1 # IF ALTSAVE IS NEGATIVE, ZERO ALTSAVE
TS ALTSAVE +1 # AND ALTSAVE +1 AT ZERODATA.
## Page 893
CAF ZERO
AD POSMAX
AD ALTSAVE
TS ALTSAVE # POSSIBLY SKIP TO NEWDATA.
TCF ZERODATA
NEWDATA CCS ALTSAVE +1
TCF +4
TCF +3
CAF ZERO # SET NEGATIVE ALTSAVE +1 TO +0.
TS ALTSAVE +1
CCS ALTSAVE # PROVIDE A 15 BIT UNSIGNED OUTPUT.
CAF BIT15 # THE HI-ORDER PART IS +1 OR +0.
AD ALTSAVE +1
TCF DATAOUT # DISPATCH UNSIGNED BITS TO ALTM REG.
DISINDAT EXTEND
QXCH LADQSAVE # SAVE RETURN TO ALTROUT +1 OR ALTOUT +1
CS FLAGWRD1 # YES. CHECK STATUS OF DIDFLAG.
MASK DIDFLBIT
EXTEND
BZF SPEEDRUN # SET. PERFORM DATA DISPLAY SEQUENCE.
CS FLAGWRD1 # RESET. PERFORM INITIALIZATION FUNCTIONS.
MASK DIDFLBIT
ADS FLAGWRD1 # SET DIDFLAG.
CS BIT7
MASK IMODES33 # TO DISPLAY ALTRATE FIRST AND ALT. SECOND
TS IMODES33
CS FLAGWRD0 # ARE WE IN DESCENT TRAJECTORY?
MASK R10FLBIT
EXTEND
BZF TASKOVER # NO
CAF BIT8 # YES.
EXTEND
WOR CHAN12 # SET DISPLAY INERTIAL DATA OUTBIT.
CAF ZERO
TS TRAKLATV # LATERAL VELOCITY MONITOR FLAG
TS TRAKFWDV # FORWARD VELOCITY MONITOR FLAG
TS LATVMETR # LATVEL MONITOR METER
TS FORVMETR # FORVEL MONITOR METER
CAF BIT4
TC TWIDDLE
ADRES INTLZE
TCF TASKOVER
INTLZE CAF BIT2
EXTEND
WOR CHAN12 # ENABLE RR ERROR COUNTER.
## Page 894
CS IMODES33
MASK BIT8
ADS IMODES33 # SET INERTIAL DATA FLAG.
TCF TASKOVER
SPEEDRUN CS PIPTIME +1 # UPDATE THE VELOCITY VECTOR
AD TIME1 # COMPUTE T - TN
AD HALF # CORRECT FOR POSSIBLE OVERFLOW OF TIME1.
AD HALF
XCH DT # SAVE FOR LATER USE
CA 1SEC
TS ITEMP5 # INITIALIZE FOR DIVISION LATER
EXTEND
DCA GDT/2 # COMPUTE THE X-COMPONENT OF VELOCITY.
DDOUBL
DDOUBL
EXTEND
MP DT
EXTEND
DV ITEMP5
XCH VVECT # VVECT = G(T-TN) M/CS *2(-5)
EXTEND
DCA V # M/CS *2(-7)
DDOUBL # RESCALE TO 2(-5)
DDOUBL
ADS VVECT # VVECT = VN + G(T-TN) M/CS *2(-5)
CA PIPAX # DELV CM/SEC *2(-14)
AD PIPATMPX # IN CASE PIPAX HAS BEEN ZEROED
EXTEND
MP KPIP1(5) # DELV M/CS *2(-5)
ADS VVECT # VVECT = VN + DELV + GN(T-TN) M/CS *2(-5)
EXTEND
DCA GDT/2 +2 # COMPUTE THE Y-COMPONENT OF VELOCITY.
DDOUBL
DDOUBL
EXTEND
MP DT
EXTEND
DV ITEMP5
XCH VVECT +1
EXTEND
DCA V +2
DDOUBL
DDOUBL
ADS VVECT +1
CA PIPAY
AD PIPATMPY
EXTEND
MP KPIP1(5)
ADS VVECT +1
## Page 895
EXTEND
DCA GDT/2 +4 # COMPUTE THE Z-COMPONENT OF VELOCITY.
DDOUBL
DDOUBL
EXTEND
MP DT
EXTEND
DV ITEMP5
XCH VVECT +2
EXTEND
DCA V +4
DDOUBL
DDOUBL
ADS VVECT +2
CA PIPAZ
AD PIPATMPZ
EXTEND
MP KPIP1(5)
ADS VVECT +2
CAF BIT3 # PAUSE 40 MS TO LET OTHER RUPTS IN.
TC VARDELAY
CA DELVS # HI X OF VELOCITY CORRECTION TERM.
AD VVECT # HI X OF UPDATED VELOCITY VECTOR.
TS ITEMP1 # = VX - DVX M/CS *2(-5).
CA DELVS +2 # Y
AD VVECT +1 # Y
TS ITEMP2 # = VY - DVY M/CS *2(-5).
CA DELVS +4 # Z
AD VVECT +2 # Z
TS ITEMP3 # = VZ - DVZ M/CS *2(-5).
CA ITEMP1 # COMPUTE VHY, VELOCITY DIRECTED ALONG THE
EXTEND # Y-COORDINATE.
MP UHYP # HI X OF CROSS-RANGE HALF-UNIT VECTOR.
XCH RUPTREG1
CA ITEMP2
## Page 896
EXTEND
MP UHYP +2 # Y
ADS RUPTREG1 # ACCUMULATE PARTIAL PRODUCTS.
CA ITEMP3
EXTEND
MP UHYP +4 # Z
ADS RUPTREG1
CA RUPTREG1
DOUBLE
XCH VHY # VHY=VMP.UHYP M/CS*2(-5).
CA ITEMP1 # NOW COMPUTE VHZ, VELOCITY DIRECTED ALONG
EXTEND # THE Z-COORDINATE.
MP UHZP # HI X OF DOWN-RANGE HALF-UNIT VECTOR.
XCH RUPTREG1
CA ITEMP2
EXTEND
MP UHZP +2 # Y
ADS RUPTREG1 # ACCUMULATE PARTIAL PRODUCTS.
CA ITEMP3
EXTEND
MP UHZP +4 # Z
ADS RUPTREG1
CA RUPTREG1
DOUBLE
XCH VHZ # VHZ = VMP.UHZP M/CS*2(-5).
GET22/32 CAF EBANK6 # GET SIN(AOG),COS(AOG) FROM GPMATRIX.
TS EBANK
EBANK= M22
CA M22
TS ITEMP3
CA M32
TS ITEMP4
CAF EBANK7
TS EBANK
EBANK= UNIT/R/
LATFWDV CA ITEMP4 # COMPUTE LATERAL AND FORWARD VELOCITIES.
EXTEND
MP VHY
XCH RUPTREG1
CA ITEMP3
EXTEND
MP VHZ
ADS RUPTREG1 # = VHY(COS)AOG+VHZ(SIN)AOG M/CS *2(-5)
CA VELCONV # CONVERT LATERAL VELOCITY TO BIT UNITS.
EXTEND
MP RUPTREG1
DDOUBL
XCH LATVEL # LATERAL VELOCITY IN BIT UNITS *2(-14).
CA ITEMP4 # COMPUTE FORWARD VELOCITY.
EXTEND
## Page 897
MP VHZ
XCH RUPTREG1
CA ITEMP3
EXTEND
MP VHY
CS A
ADS RUPTREG1 # =VHZ(COS)AOG-VHY(SIN)AOG M/CS *2(-5).
CA VELCONV # CONVERT FORWARD VELOCITY TO BIT UNITS.
EXTEND
MP RUPTREG1
DDOUBL
XCH FORVEL # FORWARD VELOCITY IN BIT UNITS *2(-14).
CAF BIT6
EXTEND # WISHETH THE ASTRONAUT THE ANALOG
RAND CHAN30 # DISPLAYS? I.E.,
CCS A # IS THE MODE SELECT SWITCH IN PGNCS?
TCF DISPRSET # NO. ASTRONAUT REQUESTS NO INERTIAL DATA
CS FLAGWRD0 # ARE WE IN DESCENT TRAJECTORY?
MASK R10FLBIT
CCS A
TCF +2 # YES.
TC LADQSAVE # NO.
CS MAXVBITS # ACC.=-199.9989 FT./SEC.
TS ITEMP6 # -547 BIT UNITS (OCTAL) AT 0.5571 FPS/BIT
CAF ONE # LOOP TWICE.
VMONITOR TS ITEMP5 # FORWARD AND LATERAL VELOCITY LANDING
INDEX ITEMP5 # ANALOG DISPLAYS MONITOR.
CCS LATVEL
TCF +4
TCF LVLIMITS
TCF +8D
TCF LVLIMITS
INDEX ITEMP5
CS LATVEL
AD MAXVBITS # +199.9989 FT./SEC.
EXTEND
BZMF CHKLASTY
TCF LVLIMITS
INDEX ITEMP5
CA LATVEL
AD MAXVBITS
EXTEND
BZMF +2
TCF LVLIMITS
CHKLASTY INDEX ITEMP5
CCS LATVMETR
TCF +4
TCF LASTOK
TCF +7
TCF LASTOK
INDEX ITEMP5
CA LATVEL
EXTEND
BZMF LASTPOSY +5
TCF +5
INDEX ITEMP5
CS LATVEL
EXTEND
## Page 898
BZMF LASTNEGY +4
LASTOK INDEX ITEMP5
CCS TRAKLATV
TCF LASTPOSY
TCF +2
TCF LASTNEGY
INDEX ITEMP5
CA LATVEL
EXTEND
BZMF NEGVMAXY
TCF POSVMAXY
LASTPOSY INDEX ITEMP5
CA LATVEL
EXTEND
BZMF +2
TCF POSVMAXY
CS MAXVBITS
TCF ZEROLSTY
POSVMAXY INDEX ITEMP5
CS LATVMETR
AD MAXVBITS
INDEX ITEMP5
XCH RUPTREG3
CAF ONE
TCF ZEROLSTY +3
LASTNEGY INDEX ITEMP5
CA LATVEL
EXTEND
BZMF NEGVMAXY
CA MAXVBITS
TCF ZEROLSTY
NEGVMAXY INDEX ITEMP5
CA LATVMETR
AD MAXVBITS
COM
INDEX ITEMP5
XCH RUPTREG3
CS ONE
TCF ZEROLSTY +3
LVLIMITS INDEX ITEMP5
CCS TRAKLATV
TCF LATVPOS
TCF +2
TCF LATVNEG
INDEX ITEMP5
CS LATVMETR
EXTEND
BZMF +2
TCF NEGLMLV
INDEX ITEMP5
## Page 899
CS LATVEL
EXTEND
BZMF LVMINLM
AD ITEMP6
INDEX ITEMP5
AD LATVMETR
EXTEND
BZMF LVMINLM
INDEX ITEMP5
AD LATVEL
EXTEND
INDEX ITEMP5
SU LATVMETR
TCF ZEROLSTY
LATVPOS INDEX ITEMP5
CS LATVEL
EXTEND
BZMF LVMINLM
TCF +5
LATVNEG INDEX ITEMP5
CA LATVEL
EXTEND
BZMF LVMINLM
INDEX ITEMP5
CS LATVMETR
TCF ZEROLSTY
NEGLMLV INDEX ITEMP5
CA LATVEL
EXTEND
BZMF LVMINLM
CA MAXVBITS
INDEX ITEMP5
AD LATVMETR
COM
INDEX ITEMP5
AD LATVEL
EXTEND
BZMF LVMINLM
EXTEND
INDEX ITEMP5
SU LATVEL
INDEX ITEMP5
AD LATVMETR
COM
TCF ZEROLSTY
LVMINLM INDEX ITEMP5
CS LATVMETR
INDEX ITEMP5
AD LATVEL
ZEROLSTY INDEX ITEMP5
## Page 900
XCH RUPTREG3
CAF ZERO
INDEX ITEMP5
TS TRAKLATV
INDEX ITEMP5
CA RUPTREG3
AD NEG0 # AVOIDS +0 DINC HARDWARE MALFUNCTION
INDEX ITEMP5
TS CDUTCMD
INDEX ITEMP5
CA RUPTREG3
INDEX ITEMP5
ADS LATVMETR
CCS ITEMP5 # FIRST MONITOR FORWARD THEN LATERAL VEL.
TCF VMONITOR
CAF BIT2 # CHECK TO SEE IF RR ERROR COUNTERS
EXTEND # ARE ENABLED.
RAND CHAN12
CCS A # IF NOT.
TCF +2
TCF DISPRSET # RE-INITIALIZE LANDING ANALOG DISPLAYS
CAF BITSET # DRIVE THE X-POINTER DISPLAY.
EXTEND
WOR CHAN14
TC LADQSAVE # GO TO ALTROUT +1 OR TO ALTOUT +1
ZERODATA CAF ZERO # ZERO ALTSAVE AND ALTSAVE +1 - - -
TS L # NO NEGATIVE ALTITUDES ALLOWED.
TCF ZDATA2
# ************************************************************************
DISPRSET CS FLAGWRD0 # ARE WE IN DESCENT TRAJECTORY?
MASK R10FLBIT
EXTEND
BZF ABORTON # NO.
CAF BIT8 # YES.
MASK IMODES33 # CHECK IF INERTIAL DATA JUST DISPLAYED.
CCS A
CAF BIT2 # YES. DISABLE RR ERROR COUNTER
AD BIT8 # NO. REMOVE DISPLAY INERTIAL DATA
COM
EXTEND
WAND CHAN12
ABORTON CS BITS8/7 # RESET INERTIAL DATA, INTERLEAVE FLAGS.
MASK IMODES33
TS IMODES33
CS DIDFLBIT
MASK FLAGWRD1
TS FLAGWRD1 # RESET DIDFLAG.
TCF TASKOVER
# ************************************************************************
BITS8/7 OCT 00300 # INERTIAL DATA AND INTERLEAVE FLAGS.
BITSET = PRIO6
# ************************************************************************
## Page 901
## There is no source code on the original program listing.
