(16C) Linear Feedback Shift Registers

[badacktor]

I recently picked up an HP-16C and decided to try writing some linear feedback shift registers for it. wasn't feeling too ambitious, so I just replicated the two that had diagrams on wikipedia. https://en.wikipedia.org/wiki/Linear-fee...t_register

(16 bit unsigned mode, displaying leading 0s. the status screen should read 0 - 16 - 1000 or something. be sure to preload the index register with the value of however many times you want things to loop, and the X register with a seed that can be anything except all 0s.)

Code:

 Bit Extraction Subroutine 
──────────────────┬──────────────────
                  │
 001 - 43. 22. b  │ [g][LBL] B
                  │
 002 -         26 │ [BIN]
                  │
 003 -     42  6  │ [f][B?]
                  │
 004 -         1  │  1
                  │
 005 -         0  │  0
                  │
 006 -     42  b  │ [f][SR]
                  │
 007 -         23 │ [HEX]
                  │
 008 -     43  21 │ [g][RTN]
                  │

 Linear Feedback Shift Register #1 (Fibonacci)
──────────────────┬────────────────────────────
                  │
 009 - 43. 22. E  │ [g][LBL] E
                  │
 010 -         23 │ [HEX]
                  │
 011 -     44  4  │ [STO] 4
                  │
 012 -         F  │  F
                  │
 013 -     21  b  │ [GSB] B
                  │
 014 -     44  5  │ [STO] 5
                  │
 015 -     45  4  │ [RCL] 4
                  │
 016 -         d  │  D
                  │
 017 -     21  b  │ [GSB] B
                  │
 018 -     45  5  │ [RCL] 5
                  │
 019 -     42  10 │ [f][XOR]
                  │
 020 -     44  5  │ [STO] 5
                  │
 021 -     45  4  │ [RCL] 4
                  │
 022 -         C  │  C
                  │
 023 -     21  b  │ [GSB] B
                  │
 024 -     45  5  │ [RCL] 5
                  │
 025 -     42  10 │ [f][XOR]
                  │
 026 -     44  5  │ [STO] 5
                  │
 027 -     45  4  │ [RCL] 4
                  │
 028 -         A  │  A
                  │
 029 -     21  b  │ [GSB] B
                  │
 030 -     45  5  │ [RCL] 5
                  │
 031 -     42  10 │ [f][XOR]
                  │
 032 -     45  4  │ [RCL] 4
                  │
 033 -     42  A  │ [f][SL]
                  │
 034 -         40 │ [+]
                  │
 035 -     42  26 │ [f] SHOW [BIN]
                  │
 036 -     43  34 │ [g][PSE]
                  │
 037 -     43  23 │ [g][DSZ]
                  │
 038 -     22  E  │ [GTO] E
                  │
 039 -         31 │ [R/S]
                  │

 Linear Feedback Shift Register #2 (Galois)
──────────────────┬─────────────────────────
                  │
 040 - 43. 22. F  │ [g][LBL] F
                  │
 041 -         23 │ [HEX]
                  │
 042 -     44  4  │ [STO] 4
                  │
 043 -     42  d  │ [f][RR]
                  │
 044 -     44  6  │ [STO] 6
                  │
 045 -     45  4  │ [RCL] 4
                  │
 046 -         0  │  0
                  │
 047 -     21  b  │ [GSB] B
                  │
 048 -     44  7  │ [STO] 7
                  │
 049 -     45  4  │ [RCL] 4
                  │
 050 -         b  │  B
                  │
 051 -     21  b  │ [GSB] B
                  │
 052 -     45  7  │ [RCL] 7
                  │
 053 -     43  49 │ [g][x=y]
                  │
 054 -     22  0  │ [GTO] 0
                  │
 055 -     21  1  │ [GTO] 1
                  │
 056 - 43. 22. 0  │ [g][LBL] 0
                  │
 057 -     45  6  │ [RCL] 6
                  │
 058 -         A  │  A
                  │
 059 -     42  5  │ [f][CB]
                  │
 060 -     22  2  │ [GTO] 2
                  │
 061 - 43. 22. 1  │ [g][LBL] 1
                  │
 062 -     45  6  │ [RCL] 6
                  │
 063 -         A  │  A
                  │
 064 -     42  4  │ [f][SB]
                  │
 065 -     22  2  │ [GTO] 2
                  │
 066 - 43. 22. 2  │ [g][LBL] 2
                  │
 067 -     44  6  │ [STO] 6
                  │
 068 -     45  4  │ [RCL] 4
                  │
 069 -         d  │  D
                  │
 070 -     21  b  │ [GSB] B
                  │
 071 -     45  7  │ [RCL] 7
                  │
 072 -     43  49 │ [g][x=y]
                  │
 073 -     22  0  │ [GTO] 0
                  │
 074 -     22  1  │ [GTO] 1
                  │
 075 - 43. 22. 0  │ [g][LBL] 0
                  │
 076 -     45  6  │ [RCL] 6
                  │
 077 -         C  │  C
                  │
 078 -     42  5  │ [f][CB]
                  │
 079 -     22  2  │ [GTO] 2
                  │
 080 - 43. 22. 1  │ [g][LBL] 1
                  │
 081 -     45  6  │ [RCL] 6
                  │
 082 -         C  │  C
                  │
 083 -     42  4  │ [f][SB]
                  │
 084 -     22  2  │ [GTO] 2
                  │
 085 - 43. 22. 2  │ [g][LBL] 2
                  │
 086 -     44  6  │ [STO] 6
                  │
 087 -     45  4  │ [RCL] 4
                  │
 088 -         E  │  E
                  │
 089 -     21  b  │ [GSB] B
                  │
 090 -     45  7  │ [RCL] 7
                  │
 091 -     43  49 │ [g][x=y]
                  │
 092 -     22  0  │ [GTO] 0
                  │
 093 -     22  1  │ [GTO] 1
                  │
 094 - 43. 22. 0  │ [g][LBL] 0
                  │
 095 -     45  6  │ [RCL] 6
                  │
 096 -         d  │  D
                  │
 097 -     42  5  │ [f][CB]
                  │
 098 -     22  2  │ [GTO] 2
                  │
 099 - 43. 22. 1  │ [g][LBL] 1
                  │
 100 -     45  6  │ [RCL] 6
                  │
 101 -         d  │  D
                  │
 102 -     42  4  │ [f][SB]
                  │
 103 -     22  2  │ [GTO] 2
                  │
 104 - 43. 22. 2  │ [g][LBL] 2
                  │
 105 -     43  34 │ [g][PSE]
                  │
 106 -     43  23 │ [g][DSZ]
                  │
 107 -     22  F  │ [GTO] F
                  │
 108 -         31 │ [R/S]
                  │

additionally, I was talking to a friend who's got some computer science background but doesn't mess with old HP calculators a lot, and they asked if I could write an explanation for "us dirty scrubs" and I was like, oh heck, yeah!

two months later, I've got ~50 page long pdf explaining the fundamentals of computer science and RPN calculators all in service of sharing some LFSRs I wrote for the 16C. which is bananas. but it's written so that just about anyone with zero background could understand it. I'm hoping it's got enough of a light/goofy tone that it's worth reading.

I'll share it here, and if y'all got any suggestions on what I could do with it, where to send it or post it, or something, I'd appreciate that immensely! also if you see any typos. I've tried so hard to crush 'em all.

https://drive.google.com/file/d/1dDYeiRl...sp=sharing

anyway, I hope my little linear feedback shift registers are fun to play with! be well!