[resolved][puzzle] jumping counter

kuroneko

Apologies if this is common knowledge but I just found out about it and share it anyway [noparse]:)[/noparse]

What's the result returned to the caller (through par) in the following code fragment and what label does it jump to (:_5, :_6 or :_7)?

For example, (%1000_0111 and :_7) would be a valid - but wrong - answer. Solution: label :_5, result $85. Who would have guessed [noparse]:)[/noparse]

Also, don't be scared about anything before jmp cnt. The reason for having this code in there is to make sure that the lower 9 bits of cnt are 0 or slightly higher but in a controlled range. A waitcnt vscl, #0 would have done the job just as well but depending on clock speed might take a while (therefore the imposed limit of 257..512).

Note: jmp cnt/phsx is confined to one of the jump targets :_5, :_6 or :_7, i.e. it doesn't go off into nowhere.

DAT             org     0

start           movd    cnt, #2                 ' get some room
                add     cnt, cnt                ' min 257 cycles
                andn    cnt, #%111111111        ' max 512 cycles
                     
                waitcnt cnt, #0                 ' wait for $XXXXX(%xxx0)00
                jmp     cnt

:_5             add     outb, #%001
:_6             add     outb, #%010
:_7             add     outb, #%100

                or      outb, #%10000000        ' indicate result ready
                wrlong  outb, par
                
                cogid   cnt
                cogstop cnt

                fit

For people uncomfortable with waitcnt & Co here a version with ordinary counters. Functionality is the same.

DAT             org     0

start           movi    ctra, #%0_11111_000
                mov     frqa, #1
                mov     phsa, #3
                jmp     phsa

                nop
:_5             add     outb, #%0001
:_6             add     outb, #%0010
:_7             add     outb, #%0100

                or      outb, #%10000000
                wrlong  outb, par
                
                cogid   cnt
                cogstop cnt

                fit

Post Edited (kuroneko) : 12/9/2009 6:03:13 AM GMT

Cluso99

Here is my answer (untested), in an attachment so as not to spoil for others.

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Cluso99

I did not fully answer the puzzle.

Once again, not to spoil it, answer attached.

So far, 2 views to my previous answer - one is kuroneko and one is me

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Links to other interesting threads:

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My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

kuroneko

That answer was - unfortunately - wrong, but close [noparse]:)[/noparse]

Cluso99

Goofed Forgot to bring down the "1"

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
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· Prop Tools under Development or Completed (Index)
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My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

kuroneko

Don't worry, it's still wrong [noparse]:)[/noparse] You'd probably look at me funny (as in "What?!") if I told you the answer ...

Post Edited (kuroneko) : 12/7/2009 5:15:33 AM GMT

Cluso99

I have a short time before I have to go out.
Then, Propfest tonight on the Gold Coast, Australia

But I do not want to know the answer. Only that it's wrong.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

Cluso99

Next try. If I am right, gee it's tricky

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

kuroneko

That's certainly an interesting conclusion but it's still wrong. A result is in fact reported, i.e. wrlong outb, par is perfectly valid.

Cluso99

ok, it's going to have to wait until tomorrow then

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

Graham Stabler

Attached is my guess, I suspect too simple to be correct.

Graham

kuroneko

Graham Stabler said...
Attached is my guess, I suspect too simple to be correct.

The reasoning is OK but it's slightly off.

Cluso99

Ok, from what I have tried by wrong guesses, this should be the answer, but WOW. Not what I expected.

There are some guesses here for the timing diagram.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

Graham Stabler

OK,

I think I just made a simple error (not really part of puzzle perhaps)

Graham

Graham Stabler

Nope still wrong, just saw the PM.

Graham

Cluso99

The alternative without the waitcnt is much easier (I hope)

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

Graham Stabler

Yes I think that is correct.

Bare in mind I was trying to do this from the datasheet without ever having seen the thread where this is a hot topic [noparse]:([/noparse] [noparse];)[/noparse]

Graham

kuroneko

Well, we all seem to converge on label :_5 now (OK), but the reported result is NOT $87. Back to square one I'm afraid [noparse]:)[/noparse]

jazzed

My first guess was :_6, $86 ... thinking that there were two cycles from output -> R to input <- S.
Square one means learning boolean logic again? [noparse];)[/noparse] Nice teaser Kuroneko. Got any more?

kuroneko

Don't panic, boolean logic still applies [noparse]:)[/noparse] In the end we have to blame Chip for that. I was looking a bit puzzled when I stumbled upon this but if you think about it a bit more it's easy to explain. Not sure if it can be exploited in a useful way though. It certainly helps to obfuscate your code [noparse]:)[/noparse]

Cluso99

I had not thought of the implications within the add instructions - I shall extend the timing diagram to work this out later today.

The waitcnt (which means all waitxxx instructions) got me. Using the mov instructions was no problem to calculate since Chip disclosed how they work on the other thread.

However, I still need to get the waitxxx understood. I had thought that waitxxx took a minimum of 6 clocks because it causes a pipe flush but this just does not work as I expected. I will seek clarification from Chip.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

kuroneko

Cluso99 said...
I had not thought of the implications within the add instructions - I shall extend the timing diagram to work this out later today.

It's not the add instruction per se, it's all inside the jmp.

Anyway, there are only 7 possible answers left, any takers?

Graham Stabler

So we are saying that although the target is 5 is does not jump there?

kuroneko

Graham Stabler said...
So we are saying that although the target is 5 is does not jump there?

It definitely jumps there, just the overall result isn't $87 (as one would expect). To make that clear, the result is looking like this: %1000_0xx1.

Post Edited (kuroneko) : 12/8/2009 12:50:56 PM GMT

Graham Stabler

Well I know what the answer is and I know what superficially causes it but I have no idea why.

Cluso99

WOW·

Not to spoil it for anyone, But, even armed with all the info I would never have guessed the outcome.

I believe I have deduced the reason it works this way, together with the "unintended feature" and solution·· ·Remember, this example uses unintended functions/features of the prop.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

kuroneko

Solution announced in top posting. Thanks for playing!

Cluso99

kuroneko: Very difficult to see the answer in white.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

kuroneko

That was on purpose, I'll change it.

Beau Schwabe

kuroneko,

Whether you are using cnt, phsa, or whatever, the compiler sees this value as a constant... because cnt is always moving and your actually writing to a mask you must do a few strange things with the waitcnt before it syncs up to a value that works for you. ...And in the case with phsa... if you don't start ctra, the jump location becomes more predictable for you.

You could just as easily use a constant for the jump and just see how the jump really relates to where the PC (Program Counter) ends up executing the next instruction.

Example uses the Propeller DEMO board LEDs

[b]PUB[/b] start

    [b]cognew[/b](@PASM, 0)


[b]DAT[/b]

PASM            [b]jmp[/b]     #1                      '<--- #0
                                        

:_5             [b]add[/b]     [b]outb[/b], #%001             '<--- #1
:_6             [b]add[/b]     [b]outb[/b], #%010             '<--- #2
:_7             [b]add[/b]     [b]outb[/b], #%100             '<--- #3

                [b]or[/b]      [b]outb[/b], #%10000000        '<--- #4


'--------------------------------------------------------                
                [b]mov[/b]     [b]dira[/b], LEDmask           '<--- #5
                [b]shl[/b]     [b]outb[/b], #16               '<--- #6
                [b]mov[/b]     [b]outa[/b], [b]outb[/b]             '<--- #7 
                
EndlessLoop    [b]jmp[/b]      #EndlessLoop            '<--- #8                  

LEDmask        [b]long[/b]     %00000000_11111111_00000000_00000000

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 12/9/2009 7:24:29 AM GMT

kuroneko

Now I'm puzzled. What exactly are you saying?