THROTTLE_CONTROL_ROUTINES.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: THROTTLE_CONTROL_ROUTINES.agc
## Purpose: A section of an attempt to reconstruct Sundance revision 306
## as closely as possible with available information. Sundance
## 306 is the source code for the Lunar Module's (LM) Apollo
## Guidance Computer (AGC) for Apollo 9. This program was created
## using the mixed-revision SundanceXXX as a starting point, and
## pulling back features from Luminary 69 believed to have been
## added based on memos, checklists, observed address changes,
## or the Sundance GSOPs.
## Assembler: yaYUL
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 2020-07-24 MAS Created from SundanceXXX.
BANK 31
SETLOC FTHROT
BANK
EBANK= PIF
COUNT* $$/THROT
# * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
# HERE FC, DESIRED THRUST, AND FP, PRESENT THRUST, UNWEIGHTED, ARE COMPUTED.
THROTTLE CA ABDELV # COMPUTE PRESENT ACCELERATION IN UNITS OF
EXTEND # 2(-4) M/CS/CS, SAVING SERVICER TROUBLE
MP /AF/CNST
+3 EXTEND
QXCH RTNHOLD
AFDUMP TC MASSMULT
DXCH FP # FP = PRESENT THRUST
EXTEND
DCA /AFC/
TC MASSMULT
DXCH FCODD # FCODD = WHAT IT IS GOING TO GET
# IF IT HAS BEEN LESS THAN 3 SECONDS SINCE THE LAST THROTTLING, AUGMENT FP USING THE FWEIGHT CALCULATED THEN.
CS TTHROT # THIS CODING ASSUMES A FLATOUT WITHIN
AD TIME1 # 80 SECONDS BEFORE FIRST THROTTLE CALL
MASK POSMAX
COM
AD 3SECS
EXTEND
BZMF WHERETO # BRANCH IF (TIME1-TTHROT +1) > 3 SECONDS
EXTEND
DCA FWEIGHT
DAS FP
# THIS LOGIC DETERMINES THE THROTTLING IN THE REGION 10% - 94%. THE MANUAL THROTTLE, NOMINALLY SET AT
# MINIMUM BY ASTRONAUT OR MISSION CONTROL PROGRAMS, PROVIDES THE LOWER BOUND. A STOP IN THE THROTTLE HARDWARE
# PROVIDES THE UPPER.
WHERETO CS ZERO # INITIALIZE PIFPSET
TS PIFPSET
CS HIGHCRIT
AD FCOLD
EXTEND
BZMF LOWFCOLD # BRANCH IF FCOLD < OR = HIGHCRIT
CS LOWCRIT
AD FCODD
EXTEND
BZMF FCOMPSET # BRANCH IF FC < OR = LOWCRIT
CA FP # SEE NOTE 1
TCF FLATOUT1
FCOMPSET CS FMAXODD # SEE NOTE 2
AD FP
TCF FLATOUT2
LOWFCOLD CS HIGHCRIT
AD FCODD
EXTEND
BZMF DOPIF # BRANCH IF FC < OR = HIGHCRIT
CA FMAXPOS # NO: THROTTLE-UP
FLATOUT1 DXCH FCODD
CA FEXTRA
FLATOUT2 TS PIFPSET
# NOTE 1 FC IS SET EQUAL TO FP SO PIF WILL BE ZERO. THIS IS DESIRABLE
# AS THERE IS ACTUALLY NO THROTTLE CHANGE.
#
# NOTE2 HERE, SINCE WE ARE ABOUT TO RETURN TO THE THROTTLEABLE REGION
# (BELOW 55%) THE QUANTITY -(FMAXODD-FP) IS COMPUTED AND PUT
# INTO PIFPSET TO COMPENSATE FOR THE DIFFERENCE BETWEEN THE
# NUMBER OF BITS CORRESPONDING TO FULL THROTTLE (FMAXODD) AND THE
# NUMBER CORRESPONDING TO ACTUAL THRUST (FP). THUS THE TOTAL
# THROTTLE COMMAND PIF = FC - FP - (FMAXODD - FP) = FC - FMAXODD.
DOPIF TC FASTCHNG # RESTART PROTECTION
EXTEND
DCA FCODD
TS FCOLD
DXCH PIF
EXTEND
DCS FP
DAS PIF # PIF = FC - FP, NEVER EQUALS +0
DOIT CA PIF
AD PIFPSET # ADD IN PIFPSET, WITHOUT CHANGING PIF
TS PSEUDO55
TS THRUST
CAF BIT4
EXTEND
WOR CHAN14
CA TIME1
TS TTHROT
# SINCE /AF/ IS NOT AN INSTANTANEOUS ACCELERATION, BUT RATHER AN "AVERAGE" OF THE ACCELERATION LEVELS DURING
# THE PRECEEDING PIPA INTERVAL, AND SINCE FP IS COMPUTED DIRECTLY FROM /AF/, FP IN ORDER TO CORRESPOND TO THE
# ACTUAL THRUST LEVEL AT THE END OF THE INTERVAL MUST BE WEIGHTED BY
#
# PIF(PPROCESS + TL) PIF /PIF/
# FWEIGHT = ------------------ + -------------
# PGUID 2 PGUID FRATE
#
# WHERE PPROCESS IS THE TIME BETWEEN PIPA READING AND THE START OF THROTTLING, PGUID IS THE GUIDANCE PERIOD, AND
# FRATE IS THE THROTTLING RATE (32 UNITS PER CENTISECOND). PGUID IS ASSUMED TO BE 2 SECONDS. THE "TL" IN THE
# FIRST TERM REPRESENTS THE ENGINE'S RESPONSE LAG. HERE FWEIGHT IS COMPUTED FOR USE NEXT PASS.
CA 4SECS
TS Q
CS PIPTIME +1 # TIME OF LAST PIPA READING
AD TIME1
AD THROTLAG # COMPENSATE FOR ENGINE RESPONSE LAG
MASK LOW8 # MAKE SURE SMALL AND POSITIVE
ZL
EXTEND
DV Q
EXTEND
MP PIF
DOUBLE
DXCH FWEIGHT
CA 2.PG.FRT
TS Q
CCS PIF
AD ONE
TCF +2
AD ONE
EXTEND
MP PIF
EXTEND
DV Q
ZL
DAS FWEIGHT
THDUMP TC RTNHOLD
# FLATOUT THROTTLES UP THE DESCENT ENGINE, AND IS CALLED AS A BASIC SUBROUTINE.
FLATOUT CAF BIT13 # 4096 PULSES
WHATOUT TS PIFPSET # USE PIFPSET SO FWEIGHT WILL BE ZERO
CS ZERO
TS PIF
EXTEND
QXCH RTNHOLD
TCF DOIT
# MASSMULT SCALES ACCELERATION, ARRIVING IN A AND L IN UNITS OF 2(-4) M/CS/CS, TO FORCE IN PULSE UNITS.
MASSMULT EXTEND
QXCH BUF
EXTEND
MP MASS # LEAVES ODDLY SCALED FORCE IN A AND L
DXCH MPAC
TC DMP # LEAVES PROPERLY SCALED FORCE IM MPAC
ADRES SCALEFAC
DXCH MPAC +1
TC BUF
# CONSTANTS:-
FMAXMAX DEC +3882
FMAXODD DEC +3866 # THROTTLE SATURATION THRESHOLD
FMAXPOS DEC +3648 # FMAX 43245 NEWTONS
HIGHCRIT DEC 2446
LOWCRIT DEC 2135
FEXTRA = BIT7
DEC438 DEC 438
THROTLAG DEC 20 # EMPIRICALLY DETERMINED THROTTLE LAG TIME
2.PG.FRT DEC 12800
/AF/CNST DEC .13107
SCALEFAC 2DEC 51.947 B-12 # SCALES A (AT 2(-4) M/CS/CS) TIMES MASS
# (AT 2(16) KGS. ) TO PULSE UNITS.
# * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
