Re: 6809 / 6702 puzzle

From: Rhialto <rhialto_at_falu.nl>
Date: Sun, 22 Apr 2012 22:34:33 +0200
Message-ID: <20120422203433.GA20023@falu.nl>
On Sat 21 Apr 2012 at 16:34:22 +0200, Rhialto wrote:
> I've made a few actual screen shots with my camera, I'll transcribe them
> later. Not every write to EFE0 changes the value, but at least some do.

Here it is. I won't stick to the precise layout of the program since it
is less work to just copy/paste some lines and edit the values. And it
is more readable this way.

seed: 214                                     hex:D6
stb 128 asl 214 b^= 214 sta 145 asl 214  214      D6 D6
stb  64 asl 214 b^= 214 sta 133 asl 198  198      D6 C6
stb  32 asl 198 b^= 198 sta   3 asl 212  212      C6 D4
stb  16 asl 212 b^= 212 sta 113 asl  84   84      D4 54
stb   8 asl  84 b^=  84 sta 225 asl   6    6      54 06
stb   4 asl   6 b^=   6 sta 209 asl  39   39      06 27
stb   2 asl  39 b^=  39 sta  67 asl  51   51      27 33

Relevant columns:   ^^^                  ^^^
Emulator
table:      ^^^     ^^^             ^^^  ^^^

the seed is read,
stb xxx  is written,
asl xxx  is read, then shifted, then written,
b^= xxx  is read,
sta xxx  is written (calulated from the MUL instruction),
the last value is read.

seed: 51
stb 128 asl  51 b^=  51 sta  41 asl 197  197
stb  64 asl 197 b^= 197 sta 227 asl 243  243 
stb  32 asl 243 b^= 243 sta 213 asl 145  145 
stb  16 asl 145 b^= 145 sta 225 asl 161  161 
stb   8 asl 161 b^= 161 sta  23 asl 224  224 
stb   4 asl 224 b^= 224 sta   9 asl 114  114 
stb   2 asl 114 b^= 114 sta   5 asl 100  100 

seed: 100
stb 128 asl 100 b^= 100 sta 121 asl 170  170
stb  64 asl 170 b^= 170 sta  21 asl 224  224 
stb  32 asl 224 b^= 224 sta  43 asl  22   22 
stb  16 asl  22 b^=  22 sta 229 asl  33   33 
stb   8 asl  33 b^=  33 sta 163 asl  85   85 
stb   4 asl  85 b^=  85 sta  45 asl 105  105 
stb   2 asl 105 b^= 105 sta  57 asl 129  129 

seed: 129
stb 128 asl 129 b^= 129 sta  33 asl 187  187
stb  64 asl 197 b^= 197 sta 211 asl  95   95 
stb  32 asl  95 b^=  95 sta 205 asl 174  174 
stb  16 asl 174 b^= 174 sta  51 asl  38   38 
stb   8 asl  38 b^=  38 sta 205 asl  84   84 
stb   4 asl  84 b^=  84 sta  51 asl  30   30 
stb   2 asl  30 b^=  30 sta 205 asl 228  228 

seed: 228
stb 128 asl 228 b^= 228 sta 121 asl 100  100
stb  64 asl 100 b^= 100 sta 163 asl  29   29 
stb  32 asl  29 b^=  29 sta  69 asl   3    3 
stb  16 asl   3 b^=   3 sta 145 asl 141  141 
stb   8 asl 141 b^= 141 sta 235 asl  91   91 
stb   4 asl  91 b^=  91 sta 185 asl 149  149 
stb   2 asl 149 b^= 149 sta  71 asl  33   33 

seed:  33
stb 128 asl  33 b^=  33 sta  97 asl 120  120
stb  64 asl 120 b^= 120 sta 201 asl 132  132 
stb  32 asl 132 b^= 132 sta 167 asl  30   30 
stb  16 asl  30 b^=  30 sta 153 asl 178  178 
stb   8 asl 178 b^= 178 sta  53 asl  52   52 
stb   4 asl  52 b^=  52 sta 227 asl  68   68 
stb   2 asl  68 b^=  68 sta 213 asl  69   69 

These are all the ones I tried, starting from a reset.

I note that the only time the read value changes is after the sta column
in the middle (the one that corresponds to the STA at $9884, and whose
value is calculated by the MUL instruction at $9873). So either the
other ones are ignored somehow, or their effect is delayed someotherhow.

I plugged the seed and the values from the marked columns into the
emulator, and that seems to pass.


> I had some weird trouble with my ZoomFloppy copying files to the one
> working 8050 drive I had on hand. Someting, somewhere, randomly turned
> on some bit (the $20 one) in the data coming back from the drive. (The
> copy program reported things like "02, ok, 00 00" errors, and the
> directory listing looked corrupted)

(that should be "the $02 one"). One theory could be that the IEEE bus
drivers of this drive are a bit weak or slow, and that the ZoomFloppy
cares more about that than the PET.

-Olaf.
-- 
___ Olaf 'Rhialto' Seibert  -- There's no point being grown-up if you 
\X/ rhialto/at/xs4all.nl    -- can't be childish sometimes. -The 4th Doctor

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Received on 2012-04-22 21:00:05

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