6444540-B-reimplemented.obc
# The authors of this file declare that it has been placed into the
# Public Domain and may be used for any purpose whatever.
#
# Filename: 6444540-B-reimplemented.obc
# Purpose: This file contains assembly-language source code for
# the Gemini On-Board Computer (OBC) implementing (in the
# absence of actual source code from the Project Gemini
# era) a portion of the software design described by
# the surviving Detailed Math Flow known as MF-3,
# program #6444540 rev. B.
# References: General OBC: http://www.ibiblio.org/apollo/Gemini.html
# MF-3: http://www.ibiblio.org/apollo/Documents/GeminiMinnickMathFlow.pdf
# Developers: Developers who have touched this code are referenced by
# their initials, as in the following table:
# CAL Charlie Leist, one of the original OBC programmers.
# AWM Alden Minnick, one of the original OBC programmers.
# RSB Ron Burkey, editor for the Virtual AGC project.
# History: 2011-12-30 CAL Initial code submitted, via docx format.
# This contains only the Executor program,
# and a small part of the Re-entry program.
# 2012-01-08 RSB Adapted for assembly by the yaASM assembler,
# mainly by adding unallocated variables and
# constants, and minimal left-hand symbols for
# code that is referenced but not implemented.
# 2012-01-13 AWM Reviewed changes (mods submitted by CAL).
# 2012-01-14 RSB Merged the review changes. Also, moved
# the Executor from sector 17 (where I had
# mistakenly put it) to sector 00. Also,
# moved all stubbed left-hand symbols for
# Ascent, Catch-up, Rendezvous, and Standby
# to their appropriate memory sector/syllable/word,
# even though they do nothing as of yet. I've
# marked the review changes (and all side-effects
# of the review changes) with the notation
# [AWM1 ...], though some of the changes probably
# aren't directly due to Al.
# [RSB: added this huge block ------------------------------------------]
# For now, at least, store all variables referenced by the Executor and
# all general-purpose subroutines in the residual sector. They probably
# shouldn't all go there in reality, but that will have to be figured out
# later. Right now, they have to go somewhere in order to make the
# the assembly go through without errors, and this is as good a place as any.
CODE 0-17-2-000
DATA 0-17-0-000
# Variables
RETADR # For storing return addresses.
LC4A
LC4B
LC4C
LC4D
LC4E
LC10
LC14
LC30
CP78
CP80
CP135
CP136
CP137
DI10
DI11
DI13
DO05
DO14
DO21
DO61
DO62
DO64
DO65
BE
DDT
DPBO
DTBO
DYBO
DXDE
DYDE
DZDE
DXDG # [AWM1]
DYDG # [AWM1]
DZDG # [AWM1]
FX
FY
FZ
T
TEMP01
TEMP02
TEMP03
TRBIMI
TRE
TW
XDEI
YDEI
ZDEI
# Constants
KZERO OCT 0
KONE OCT 1
KMINUS DEC -1
K32 DEC 32
KP196 DEC 33
KP369 DEC 0.369
KP109 OCT 20000000
KP110 OCT 5000
KP111 DEC 180
# Routines that were referenced but that haven't been implemented as of yet.
I/O STO RETADR
HOP RETADR
AGE STO RETADR
HOP RETADR
GONGO STO RETADR
HOP RETADR
CLOCK STO RETADR
HOP RETADR
ACLMTR STO RETADR
HOP RETADR
TRS STO RETADR
HOP RETADR
# Flip to sector 00 syllable 1 for Standby code.
CODE 0-00-1-023
S93P1 HOP EXECTR # Entry point for Standby.
# Flip to sector 01 syllable 2 for Catch-up & Rendezvous code.
CODE 0-01-2-007
RE1P1 HOP EXECTR # Entry point for Rendezvous.
CODE 0-01-2-105
C1P2 HOP EXECTR # Entry point for Catch-up.
# Flip to sector 13 for Ascent code.
CODE 0-13-2-002
A591 HOP EXECTR # [AWM1: Entry point for Ascent.]
I/OA STO RETADR # Fast ascent loop, I think.
HOP RETADR
# Flip to sector 00 syllable 0 for the actual Executor code.
CODE 0-00-0-000
# [RSB: end of added block. --------------------------------------------]
# GEMINI EXECUTOR CODE
L000 CLA KONE # [AWM1: Was KZERO. "Although zero is a positive number, I suggest
# that you use KONE because sometimes there are tests for zero,
# plus, and minus results."]
STO LC4A # All operational modes =+ for first pass initialization –Standby mode
STO LC4B # Ascent mode
STO LC4C # Catch-up mode
STO LC4D # Rendezvous mode
STO LC4E # [AWM1]
EXECIN CLA KZERO # Enter here from initialization in all modes
STO CP135
STO CP136
STO CP137
CLA KONE # [AWM1: Was KZERO.]
STO DO62 # Start computations off
STO DO05 # Computer off [RSB: Changed from "D005"]
STO DO64 # SECO off
STO DO61 # Gain change off
EXECTR CLA LC4B # [RSB: changed from "EXECR".]
TMI E7831 # Ascent fast loop (I/O A)
E7832 CLA E7832A
HOP I/O # All routines except Ascent
E7832A CLA E7834
HOP GONGO # Basic check of arith + control logic
E7834 CLA E7835
HOP CLOCK # Clock subroutine
E7835 CLA E7836
HOP AGE # AGE subroutine
TMI EXECTR # If AGE request
E7836 CLA LC4B
TMI E7837
E7838 CLA E7839
HOP I/O
E7839 CLA DI11 # Mode control
TMI E786 # [RSB: removed left-hand symbol "E7834"]
E785 CLA DI10
TMI E787
E788 HOP S93P1 # Standby mode (93.1) [RSB: changed from "E788 TRA 789"]
E787 CLA DI13 # Mode control
TMI E7810 # Catch-up mode (1.2)
HOP A591 # [AWM1: Ascent Mode (59.1).]
E786 CLA DI13 # Mode control [RSB: changed left-hand symbol from "E7836"]
TMI E7812 # Re-entry mode (35.1)
TRA E7811 # Rendezvous mode (1.1)
E7831 CLA E7832A
HOP I/OA # Ascent fast loop
E7837 CLA E7839
HOP I/OA # Ascent fast loop [RSB: was "HOPA"]
# [RSB: Added this block]
E7810 HOP C1P2
E7811 HOP RE1P1
E7812 HOP R35P1
# Flip to sector 06 for the Re-entry code.
CODE 0-06-2-000
DATA 0-06-0-000
# [RSB: End of added block]
# RE-ENTRY CODE
R35P1 CLA LC4E
TMI R35P2
CLA KONE # [RSB: Removed left-hand symbol "R35P2A"]
# [AWM1: Was KZERO.]
STO LC4A
STO LC4B
STO LC4C
STO LC4D
STO LC10
STO LC14
CLA KMINUS
STO LC4E
CLA KZERO
STO TRBIMI
STO DDT
STO T
STO BE # Bank angle error
STO DYBO # Attitude command change
STO DTBO # Attitude command change
STO DPBO # Attitude command change
STO XDEI # Velocity change due to gravity
STO YDEI # Inertially fixed orthogonal axis
STO ZDEI # Referenced to center of earth: ZE = north, XE through
# celestial reference frame in equatorial plane
STO DXDG # [AWM1]
STO DYDG # [AWM1]
STO DZDG # [AWM1]
STO CP78
STO CP78
STO CP80
CLA EXECIN # COL 78.2 [RSB: This has no effect since EXECIN doesn't
# return, but I didn't change it.]
HOP EXECIN # EXECIN 78.2 [RSB: was just "HOP"]
R35P2 CLA R35P3 # [RSB: changed left-hand symbol from "R35P2A"]
HOP ACLMTR # Accelerometer subroutine
R35P3 CLA LC10
TMI R39P1 # [RSB: was "R35P5"]
CLA FX # Update components of retro thrust
MPY K32 # 32 decimal = 2 to the 6 power
NOP
SPQ TEMP01
ADD DXDE
STO DXDE
CLA FY
MPY K32
NOP
SPQ TEMP02
ADD DYDE
STO DYDE
CLA FZ
MPY K32
NOP
SPQ TEMP03
ADD DZDE
STO DZDE
CLA R94P4
HOP I/O
R94P4 CLA KZERO # [RSB: Changed from "R9494"]
STO DO21 # TRS Enter
CLA KMINUS
STO DO65 # TR Gate
R94P4B CLA KP196 # KP196 = 33B25
R94P4C SUB KONE # KONE = +1 [RSB: Added the left-hand symbol "R94P4C"]
TNZ R94P4C
CLA KZERO
R94P1 STO DO14 # Reset transfer gate
R94P1C CLA R35P2A
HOP TRS # TRSENT subroutine
R35P2A STO TRE # Time to Retrograde in sec
RSU KP369 # Time to Retro less than 300 B22 sec
TMI R35P2E # [RSB: was "K35P2E"]
R35P2B CLA KMINUS # By Pass DCS
STO LC30
TRA R35P2C
R35P2F CLA KZERO
STO DXDE
STO DYDE
STO DZDE
TRA R35P3
R35P2E CLA KZERO
STO LC30
# TRA K35P2C [RSB: Commented out this entire line]
R35P2C CLA TRE
SUB KP109 # 2B22 sec
TMI R35P2BB # [RSB: changed from "R35P2B"]
# [RSB: added all the stuff between here and the next bracketed comment]
CLA KZERO
STO DXDE
STO DYDE
STO DZDE
TRA R35P3A
# [RSB: end of added block]
R35P2BB CLA DXDE # [RSB: changed left-hand symbol from "R35P2B",
# which was already used above.]
SUB KP110 # KP110 = 5B9 FT/SEC
TMI R35P2G
R35P2H CLA T # Zero at start of Retro instructions - negative time
ADD KP111 # KP119 = 180 bit/sec
STO TW # Time to begin initial calculations
TRA R36P3 # To Col 36.1 EXECUTOR
R35P3A CLA EXECIN # Executor (COL 78.3) [RSB: The CLA has no effect,
# didn't change. "R35P3" already used, changed to "R35P3A".]
HOP EXECTR # GO TO EXECUTOR [RSB: Was just "HOP".]
R35P2G CLA T
SUB TW
TMI R35P3A # [RSB: changed from "R35P3"]
TRA R36P1 # RETRO THRUST SEQUENCE COMPLETE – (continue with Re-entry)
# [RSB: Added this block]
# Code referenced but not implemented yet.
R35P5 HOP EXECTR
R36P1 HOP EXECTR
R36P3 HOP EXECTR
R39P1 HOP EXECTR
# [RSB: End of added block]
