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PostPosted: Wed Sep 18, 2013 12:22 am 
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After moving the IO page of my CHOCHI boards to page 2 (to gain more contiguous RAM), I broke FIG-FORTH.

I fixed the IO, and Forth starts up, prints "fig-FORTH 1.0"<cr> as usual. After that, hitting keys just echoes and crashes (hitting enter scrolls pretty far before locking up).

I suspect that page 2 is used for some buffer somewhere, and will start searching now. Although I hope someone who knows will set me straight before I waste too much time...Thanks

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PostPosted: Wed Sep 18, 2013 1:40 am 
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Dunno if this'll help, but I dragged out a version of FIG Forth that I was running last year on the Kowalski simulator. At the time I had to tweak it to get it to assemble & run, although I don't recall all the reasons. Anyway, the following excerpt seems pertinent. Note I wasn't relocating Forth, merely trying to get it to run at $0200 & up. The first and last line of this excerpt have been tweaked.

Changing the ORG statement should let you relocate, to $0300 for example. Does this make sense, or am I not grasping the problem? Are you able to tell us where the header for LIT is located? Better yet, at what address does the label ENTER appear?

Code:
          .ORG $0200 ;tweak. Was:          *=*+2
;
                         ; User cold entry point
ENTER     NOP            ; Vector to COLD entry
          JMP COLD+2     ;
REENTR    NOP            ; User Warm entry point
          JMP WARM       ; Vector to WARM entry
          .WORD $0004    ; 6502 in radix-36
          .WORD $5ED2    ;
          .WORD NTOP     ; Name address of MON
          .WORD $7F      ; Backspace Character
          .WORD UAREA    ; Initial User Area
          .WORD TOS      ; Initial Top of Stack
          .WORD $1FF     ; Initial Top of Return Stack
          .WORD TIBX     ; Initial terminal input buffer
;
;
          .WORD 31       ; Initial name field width
          .WORD 0        ; 0=nod disk, 1=disk
          .WORD TOP      ; Initial fence address
          .WORD TOP      ; Initial top of dictionary
          .WORD VL0      ; Initial Vocabulary link ptr.
;
;    The following offset adjusts all code fields to avoid an
;    address ending $XXFF. This must be checked and altered on
;    any alteration , for the indirect jump at W-1 to operate !
;
         *=*+2 ;tweak  was: .ORIGIN *+2 whereas my Fig listing says *=*+2

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Last edited by Dr Jefyll on Wed Sep 18, 2013 1:50 am, edited 1 time in total.

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PostPosted: Wed Sep 18, 2013 1:49 am 
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My copy starts at $400
Code:
TIBX            =     $0100             ;terminal input buffer of 84 bytes.
ORIG            =     $0400             ;origin of FORTH's Dictionary.

It assembles fine, and the listing looks right. But it crashes after the initial prompt on keyboard input. I am at a bit of a loss, will have to look some more.

Oh, as for LIT:
Code:
0448 : 834c49d4         L22             db    $83,"LI",$D4      ;<--- name fie
                        ;                          <----- link field
044c : 0000                             dw    00                ;last link mar
044e : 5004             LIT             dw    *+2               ;<----- code a
0450 : b1af                             lda   (IP),y            ;<----- start

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PostPosted: Wed Sep 18, 2013 2:07 am 
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Strange! So you're saying this works
Code:
ORIG            =     $0200             ;origin of FORTH's Dictionary.

and this doesn't? No other changes?
Code:
ORIG            =     $0400             ;origin of FORTH's Dictionary.

-- Jeff

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PostPosted: Wed Sep 18, 2013 2:53 am 
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enso wrote:
My copy starts at $400
Code:
TIBX            =     $0100             ;terminal input buffer of 84 bytes.
ORIG            =     $0400             ;origin of FORTH's Dictionary.

It assembles fine, and the listing looks right. But it crashes after the initial prompt on keyboard input. I am at a bit of a loss, will have to look some more.


The first thing that comes to mind for me is that your TIB overlaps your stack space, and thus you should double-check your stack pointer... Or just relocate the TIB to $300, so as to avoid both your stack space and your I/O page.


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PostPosted: Wed Sep 18, 2013 3:43 am 
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It's actually a little different: $400 was always the bottom of the system. Previously my IO page was at $C000, and it worked. Now my IO page is at $200 (it should be OK there as nothing else sits there), and it doesn't work. The fact that it spits gobs of stuff to the serial port indicates that something is stepping on page 2.

TIB was always at $100, and the comments indicate that it uses the bottom 84 bytes, leaving plenty of room for the stack, so it shouldn't matter.

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PostPosted: Wed Sep 18, 2013 3:49 am 
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Quote:
Now my IO page is at $200
Any chance the IO page is larger than it ought to be? (Might it extend past $0400 I mean.)

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PostPosted: Wed Sep 18, 2013 3:58 am 
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My cheap debugging strategy is at http://wilsonminesco.com/6502primer/debug.html, in "Part II, Software." I would just start putting in a beep in different places to see if it gets there before crashing. It it takes a minute or two for each try (re-assembling and putting the new image in your memory), that still gets you 15 tries in 15-30 minutes. 15 tries should be more than enough. It's how I got my '816 Forth and loads of other things going.

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PostPosted: Wed Sep 18, 2013 5:33 am 
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The IO page is only 16 bytes long currently.

I'll do some more debugging tomorrow. I usually do thing similar to Garth's approach. I have an LED if the IO port fails.

It only takes a few seconds to reassemble and load code.

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PostPosted: Wed Sep 18, 2013 4:05 pm 
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I think the problem is with my address decoding (damaged while moving the IO address). Will work on the memory test.

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PostPosted: Wed Sep 18, 2013 9:35 pm 
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It was my issue after all. Back to working order. Thanks for all answers.

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