AGS_INITIALIZATION.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: AGS_INITIALIZATION.agc
## Purpose: A section of Luminary 1C, revision 131.
## It is part of the source code for the Lunar Module's (LM)
## Apollo Guidance Computer (AGC) for Apollo 13.
## 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. 208-212
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 05/05/03 RSB. Began transcribing.
## 05/14/05 RSB Corrected website reference above.
## 2017-01-06 RSB Page numbers now agree with those on the
## original harcopy, as opposed to the PDF page
## numbers in 1701.pdf.
## 2017-02-22 RSB Proofed comment text using octopus/ProoferComments.
## Page 208
# PROGRAM NAME: AGS INITIALIZATION (R47)
#
# WRITTEN BY: RHODE/KILROY/FOLLETT
#
# MOD NO.: 0
# DATE: 23 MARCH 1967
# MOD BY: KILROY
#
# MOD NO.: 1
# DATE: 28 OCTOBER 1967
# MOD BY: FOLLETT
#
# FUNCT. DESC.: (1) TO PROVIDE THE AGS ABORT ELECTRONICS ASSEMBLY (AEA) WITH THE LEM AND CSM STATE VECTORS
# (POSITION,VELOCITY,TIME) IN LEM IMU COORDINATES BY MEANS OF THE LGC DIGITAL DOWNLINK.
#
# (2) TO ZERO THE ICDU, LGC AND AEA GIMBAL ANGLE COUNTERS SIMULTANEOUSLY IN ORDER TO ESTABLISH A
# COMMON ZERO REFERENCE FOR THE MEASUREMENT OF GIMBAL (EULER) ANGLES WHICH DEFINE LEM ATTITUDE
#
# (3) TO ESTABLISH THE GROUND ELAPSED TIME OF AEA CLOCK ZERO. (IF AN AEA CLOCK ZERO IS
# REQUESTED DURING THIS PROGRAM
#
# LOG SECTION: AGS INITIALIZATION
#
# CALLING SEQ: PROGRAM IS ENTERED WHEN ASTRONAUT KEYS V47E ON DSKY.
# R47 MAY BE CALLED AT ANY TIME EXCEPT WHEN ANOTHER EXTENDED VERB IS IN PROGRESS
#
# SUBROUTINES
# CALLED:
#
# NORMAL EXIT: ENDEXT
#
# ALARM/ABORT: ALARM - BAD REFSMMAT - CODE:220
# OPERATOR ERROR IF V47 SELECTED DURING ANOTHER EXTENDED VERB.
#
# ERASABLES
# USED: SAMPTIME (2) TIME OF :ENTER: KEYSTROKE
# AGSK (2) GROUND ELAPSED TIME OF THE AEA CLOCK :ZERO:
# AGSBUFF (140) CONTAINS AGS INITIALIZATION DATA (SEE :OUTPUT: BELOW)
# AGSWORD (1) PREVIOUS DOWNLIST SAVED HERE
EBANK= AGSBUFF
BANK 40
SETLOC R47
BANK
COUNT* $$/R47
AGSINIT CAF REFSMBIT
MASK FLAGWRD3 # CHECK REFSMFLG.
CCS A
## Page 209
TC REDSPTEM # REFSMMAT IS OK
TC ALARM # REFSMMAT IS BAD
OCT 220
TC ENDEXT
NEWAGS EXTEND
DCA SAMPTIME # TIME OF THE :ENTER: KEYSTROKE
DXCH AGSK # BECOMES NEW AEA CLOCK :ZERO:
REDSPTEM EXTEND
DCA AGSK
DXCH DSPTEMX
AGSDISPK CAF V06N16
TC BANKCALL # R1 = 00XXX. HRS., R2 = 000XX MIN.,
CADR GOMARKF # R3 = 0XX.XX SEC.
TC ENDEXT # TERMINATE RETURN
TC AGSVCALC # PROCEED RETURN
CS BIT6 # IS ENTER VIA A V32
AD MPAC
EXTEND
BZF NEWAGS # YES, USE KEYSTROKE TIME FOR NEW AGSK
EXTEND # NO, NEW AGSK LOADED VIA V25
DCA DSPTEMX # LOADED INTO DSPTEMX BY KEYING
TC REDSPTEM -1 # V25E FOLLOWED BY HRS.,MINS.,SECS.
# DISPLAY THE NEW K
AGSVCALC TC INTPRET
SET
NODOFLAG # DONT ALLOW V37
SET EXIT
XDSPFLAG
CAF V06N16
TC BANKCALL
CADR EXDSPRET
TC INTPRET # EXTRAPOLATE LEM AND CSM STATE VECTORS
RTB # TO THE PRESENT TIME
LOADTIME # LOAD MPAC WITH TIME2,TIME1
STCALL TDEC1 # CALCULATE LEM STATE VECTOR
LEMPREC
CALL # CALL ROUTINE TO CONVERT TO SM COORDS AND
SCALEVEC # PROVIDE PROPER SCALING
STODL AGSBUFF # (LEMPREC AND CSMPREC LEAVE TDEC1 IN TAT)
TAT # TAT = TIME TO WHICH RATT1 AND VATT1 ARE
STCALL TDEC1 # COMPUTED (CSEC SINCE CLOCK START B-28).
CSMPREC # CALCULATE CSM STATE VECTOR FOR SAME TIME
CALL
SCALEVEC
## Page 210
STODL AGSBUFF +6
TAT
DSU DDV # CALCULATE AND STORE THE TIME
AGSK
TSCALE
STORE AGSBUFF +12D
EXIT
CAF LAGSLIST
TS DNLSTCOD
CAF 20SEC # DELAY FOR 20 SEC WHILE THE AGS
TC BANKCALL # DOWNLIST IS TRANSMITTED
CADR DELAYJOB
CA AGSWORD
TS DNLSTCOD # RETURN TO THE OLD DOWNLIST
CAF IMUSEBIT
MASK FLAGWRD0 # CHECK IMUSE FLAG.
CCS A
TC AGSEND # IMU IS BEING USED - DO NOT ZERO
CKSTALL CCS IMUCADR # CHECK FOR IMU USAGE WHICH AVOIDS THE
TCF +3 # IMUSE BIT: I.E., IMU COMPENSATION.
TCF +6 # FREE. GO AHEAD WITH THE IMU ZERO.
TCF +1
+3 CAF TEN # WAIT .1 SEC AND TRY AGAIN.
TC BANKCALL
CADR DELAYJOB
TCF CKSTALL
+6 TC BANKCALL # IMU IS NOT IN USE
CADR IMUZERO # SET IMU ZERO DISCRETE FOR 320 MSECS
TC BANKCALL # WAIT 3SEC FOR COUNTERS TO INCREMENT
CADR IMUSTALL
TC AGSEND
AGSEND TC DOWNFLAG # ALLOW V37
ADRES NODOFLAG
CAF V50N16
TC BANKCALL
CADR GOMARK3
TCF ENDEXT
TCF ENDEXT
TC ENDEXT
SCALEVEC VLOAD MXV
VATT1
REFSMMAT
VXSC VSL2
VSCALE
## Page 211
VAD VAD # THIS SECTION ROUNDS THE VECTOR, AND
AGSRND1 # CORRECTS FOR THE FACT THAT THE AGS
AGSRND2 # IS A 2 S COMPLIMENT MACHINE WHILE THE
RTB # LGC IS A 1 S COMPLIMENT MACHINE.
VECSGNAG
STOVL VATT1
RATT1
MXV VXSC
REFSMMAT
RSCALE
VSL8 VAD # AGAIN THIS SECTION ROUNDS. TWO VECTORS
AGSRND1 # ARE ADDED TO DEFEAT ALSIGNAG IN THE
VAD RTB # CASE OF A HIGH-ORDER ZERO COUPLED WITH
AGSRND2 # A LOW ORDER NEGATIVE PART.
VECSGNAG
LXA,1
VATT1
SXA,1 LXA,1
MPAC +1
VATT1 +2
SXA,1 LXA,1
MPAC +4
VATT1 +4
SXA,1 RVQ
MPAC +6
LAGSLIST = ONE
V01N14 VN 0114
V50N00A VN 5000
V00N25 EQUALS OCT31
V06N16 VN 0616
V00N34 EQUALS 34DEC
V50N16 VN 5016
TSCALE 2DEC 100 B-10 # CSEC TO SEC SCALE FACTOR
20SEC DEC 2000
RSCALE 2DEC 3.280839 B-3 # METERS TO FEET SCALE FACTOR
VSCALE 2DEC 3.280839 E2 B-9 # METERS/CS TO FEET/SEC SCALE FACTOR
AGSRND1 2OCT 0000060000
2OCT 0000060000
2OCT 0000060000
AGSRND2 2OCT 0000037777
2OCT 0000037777
## Page 212
2OCT 0000037777
SBANK= LOWSUPER # FOR SUBSEQUENT LOW 2CADRS.
