[DM16]/(16C) Linear Feedback Shift Registers

Contributed software for the DM10, DM11, DM12, DM15 and DM16 goes here.

Please prefix the subject of your post with the model of the calculator that your program is for.
Post Reply
User avatar
badacktor
Posts: 11
Joined: Fri Mar 19, 2021 7:28 pm

[DM16]/(16C) Linear Feedback Shift Registers

Post by 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-fe ... 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: Select all

 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/1ZrdZf9 ... sp=sharing

anyway, I hope my little linear feedback shift registers are fun to play with! be well!
Attachments
HP16C_LFSR.pdf
(150.58 KiB) Downloaded 29 times
pwarden42
Posts: 5
Joined: Mon May 10, 2021 12:32 pm

Re: [DM16]/(16C) Linear Feedback Shift Registers

Post by pwarden42 »

For the "get bit" routine I would probably use masking instead of branching, something like:
[g][LBL] B
[f][RRn]
1
[f][AND]
[RTN]

If you really wanted to use branching, you could use the carry flag:
[g][LBL] B
[g][CF] 4
[f][B?]
[g][SF] 4
0
[g][RLC]
[RTN]

Edit: Forgot prefix key for [RRn].
Last edited by pwarden42 on Wed Jul 07, 2021 1:45 am, edited 1 time in total.
User avatar
badacktor
Posts: 11
Joined: Fri Mar 19, 2021 7:28 pm

Re: [DM16]/(16C) Linear Feedback Shift Registers

Post by badacktor »

YO! pwarden42! You're my new favorite person! These alternate "get bit" subroutines are so dang cool, and I got so dang excited about them, I wrote about them in that already stupidly long, and now stupidly longer, pdf. You've been credited and thanked and praised. I'll drop a link to the newest, shiniest version which includes this new addendum. It starts on page... *checks notes* ...63???? Yikes.

thanks again, bud! dang!

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

(can't promise I've squashed all or even most of the typos in this new section, but I'm just so excited, I couldn't wait.)
User avatar
Coyotte
Posts: 10
Joined: Sat Sep 28, 2019 3:59 pm
Location: Liège (BE)

Re: [DM16]/(16C) Linear Feedback Shift Registers

Post by Coyotte »

Hi Badacktor,
If your PDF is long and even growing longer now, it is not stupid !
I found it very interesting (and now even more interesting ;) ) for guys like me who discover HP16C programming.

Please, continue to write "more and more stupidly long" pdf for us :D
Thanks a lot,

Coyotte
User avatar
badacktor
Posts: 11
Joined: Fri Mar 19, 2021 7:28 pm

Re: [DM16]/(16C) Linear Feedback Shift Registers

Post by badacktor »

aw gosh, thank you very much, that's super encouraging to hear. I'll try my best, I know I want to actually dig up some interesting machine code level stuff from some actual (probably old 8-bit) computer in the future and try to replicate it on the 16C. if I do, I'll probably end up excitedly writing about that.

plus I'd like to write about the overflow flag, and the signed 1s and 2s complement modes. maybe about the weird stuff that happens when you jump from integer mode to floating point mode and back. mostly to help myself understand it. I've found writing all of this stuff has been incredible just for teaching myself new stuff.

we'll see what I can do, I guess! thanks again, y'all are swell.
Post Reply