From 6fb37d5f47629817a5092da40217bde5ca0ed4fa Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sun, 4 Apr 2021 14:16:27 -0700
Subject: Very fancy improved Fibonacci machine, with HDL convert-to-ASCII
 functionality

---
 mem/mem.hex | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 66 insertions(+), 12 deletions(-)

(limited to 'mem/mem.hex')

diff --git a/mem/mem.hex b/mem/mem.hex
index 63038e3..d30c5b6 100644
--- a/mem/mem.hex
+++ b/mem/mem.hex
@@ -1,25 +1,79 @@
 @0
 
-000 // loop: acc= 0
-140 // load 0x40
+// Reset state is acc=0 idx=0
+
+000 // loop: acc= 0     # Print from 0x70 until we find a 0x00 byte
+170 // ladd 0x70
 300 // ifeq 0
 402 // jmp fib
 f44 // ++idx tx
 4fa // jmp loop
-f20 // fib: idx
-240 // store 0x40
+f20 // fib: idx         # N.B. acc is 0 at this point (we got here from ifeq 0)
+270 // store 0x70       # 0x70 is now beginning of Fibonacci sequence (0)
 001 // acc= 1
-241 // store 0x41
+271 // store 0x71       # 0x71 is 1
 000 // fibloop: acc= 0
-140 // load 0x40
-f44 // tx ++idx
-140 // load 0x40
-241 // store 0x41
-4fa // jmp fibloop
+f10 // swap
+332 // ifeq 50
+42b // jmp fullydone
+26f // store 0x6f       # 0x6f is current index into Fibonacci sequence
+f10 // swap
+170 // ladd 0x70        # Load next unprinted number in Fibonacci sequence
+f10 // swap
+000 // acc= 0
+f10 // swap
+56b // ascii 0x6b       # LSB of ASCII rep
+56c // ascii 0x6c
+56d // ascii 0x6d
+56e // ascii 0x6e       # MSB of ASCII rep
+004 // acc= 4
+f10 // swap
+f08 // scan: --idx
+000 // acc= 0
+16b // ladd 0x6b
+f10 // swap
+300 // ifeq 0
+412 // jmp allzeroes
+f10 // swap
+330 // ifeq 0x30
+4f7 // jmp scan
+f40 // done: tx
+f10 // swap
+300 // ifeq 0
+404 // jmp space
+f12 // --acc swap
+000 // acc= 0
+16b // ladd 0x6b
+4f8 // jmp done
+020 // space: acc= 0x20
+f40 // tx
+000 // acc= 0
+f20 // idx
+16f // ladd 0x6f
+f10 // swap
+402 // jmp nextfib
+f10 // allzeroes: swap
+4ef // jmp done
+170 // nextfib: ladd 0x70   # Load just-printed Fibonacci number
+171 // ladd 0x71            # Add about-to-print Fibonacci number
+272 // store 0x72           # Store n+2 Fibonacci number
+f04 // ++idx
+4d1 // jmp fibloop
+021 // fullydone: acc= 0x21
+f40 // tx
+f80 // halt
+
+@6c
+
+000 // 6b: LSB of ASCII rep
+000 // 6c: USB of ASCII rep
+000 // 6d: USB of ASCII rep
+000 // 6e: MSB of ASCII rep
+000 // 6f: next index to store in memory image of Fibonacci sequence
 
-@40
+@70
 
-048 // H
+048 // H    # later: start of in-memory Fib sequence
 065 // e
 06c // l
 06c // l
-- 
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