[Coco] More Color Forth
Arthur Flexser
flexser at fiu.edu
Sun Jan 25 15:16:50 EST 2015
To tell the truth, Stephen, it's many years since I wrote the code that I
based my message on, and I've long since forgotten the fine details of
whatever logic was behind it. All that you say sounds logical, and I don't
know why your code didn't work as expected. It does appear that the
contents of the stack, not the registers, is what matters when you jump
into the savem ROM code. All I can suggest is to try it the way I
suggested and see if it works any better.
Art
On Sun, Jan 25, 2015 at 3:08 PM, Stephen Pereira <spereira1952 at comcast.net>
wrote:
> Hi Art,
>
> Thanks very much for your response.
>
> Yes, I know what you are saying. This is probably something that I am not
> understanding as I read the disassembly of the Disk Basic code.
>
> Here is the code I am looking at (I truncated the comments):
>
> 2124 CF7E CC 02 00 LDD #$0200 * FILE TYPE=2, ASCI
> 2125 CF81 FD 09 57 STD DFLTYP *
> 2126 CF84 BD CA 04 JSR LCA04 GET NEXT UNOPEN FIL
> 2127 CF87 4F CLRA *ZERO FLAG - FIRST
> 2128 CF88 8D 2B BSR LCFB5 *WRITE A BYTE TO BU
> 2129 CF8A EC 62 LDD $02,S GET END ADDRESS
> 2130 CF8C A3 64 SUBD $04,S SUBTRACT THE START
> 2131 CF8E C3 00 01 ADDD #$0001 THE SAVED DATA BLOC
> 2132 CF91 1F 02 TFR D,Y SAVE LENGTH IN Y
> 2133 CF93 8D 1E BSR LCFB3 WRITE FILE LENGTH T
> 2134 CF95 EC 64 LDD $04,S GET THE START ADDRE
> 2135 CF97 8D 1A BSR LCFB3 WRITE OUT THE START
> 2136 CF99 AE 64 LDX $04,S GET START ADDRESS
> 2137 CF9B A6 80 LCF9B LDA ,X+ GRAB A BYTE
> 2138 CF9D BD CC 24 JSR LCC24 WRITE IT OUT
> 2139 CFA0 31 3F LEAY -1,Y DECREMENT BYTE COUN
> 2140 CFA2 26 F7 BNE LCF9B BRANCH IF ALL BYTES
> 2141 CFA4 86 FF LDA #$FF FIRST BYTE OF POSTA
> 2142 CFA6 8D 0D BSR LCFB5 WRITE IT OUT - EOF
> 2143 CFA8 4F CLRA * FIRST ARGUMENT OF
> 2144 CFA9 5F CLRB * A DUMMY - ZERO VA
> 2145 CFAA 8D 07 BSR LCFB3 WRITE OUT POSTAMBLE
> 2146 CFAC 35 36 PULS A,B,X,Y GET CONTROL ADDRESS
> 2147 CFAE 8D 03 BSR LCFB3 WRITE OUT THE TRANS
> 2148 CFB0 7E A4 2D JMP LA42D GO CLOSE ALL FILES
>
> Because of my prior experience with the 8080, I am probably not reading
> the code correctly.
>
> In line 2129 when it says LDD $02,S doesn’t that mean to get the address
> 2 bytes down from the top of stack and put them into registers A and B?
>
> In line 2130 when it says SUBD $04,S doesn’t that mean to subtract the
> address 4 bytes down from the top of stack from registers A and B?
>
> In line 2134 when it says LDD $04,S doesn’t that mean to get the address
> 4 bytes down from the top of stack and put them into registers A and B?
>
> In line 2132 I see TFR D,X and in line 2136 I see LDX $04,S, so I thought
> that the code loads the X register on its own.
>
> That is how I am interpreting what I see. If that is not correct, there
> is my problem! This is why I thought that I only have to have the
> addresses on the stack, and I cannot see where I have to have them in other
> registers.
>
> I am not trying to be argumentative - I am only trying to learn by saying
> what I thought I was reading. I greatly appreciate any advice and counsel
> that you may offer.
>
> smp
> --
> Stephen M. Pereira
> Bedford, NH 03110
> KB1SXE
>
> > On Jan 25, 2015, at 2:30 PM, Arthur Flexser <flexser at fiu.edu> wrote:
> >
> > If the description I gave you earlier, based on some old code of mine
> that
> > I unearthed, is right, then what you did isn't quite in accord with it.
> > You need to push all the registers, after loading them with the start,
> end,
> > exec, and address for resuming execution, in a SINGLE pshs operation,
> which
> > will ensure the correct order of what is pushed. Then JMP (not JSR) to
> the
> > savem routine. I'm not sure your final PULS is reached, unless you set
> the
> > resume address to that.
> >
> > Art
> >
> > On Sun, Jan 25, 2015 at 2:01 PM, Stephen Pereira <
> spereira1952 at comcast.net>
> > wrote:
> >
> >> Hello again, all,
> >>
> >> In my continuing Color Forth project, I am attempting to install a brute
> >> force save of the Color Forth code screens to disk. When I am
> eventually
> >> successful, I hope to at least be able to save and load the entire set
> of
> >> Color Forth screens 1-8 to and from disk, so we can be free from
> >> pre-loading only one set of screens 1-8 as it is now.
> >>
> >> I am hoping to use the SAVEM (and LOADM) command from DECB.
> >>
> >> I am a pretty good programmer in 8080 machine language, but I am an
> >> outright beginner on the 6809. Please forgive my non-optimal code for
> >> now. I am only hoping to get something going and then look for doing it
> >> well after I understand it all.
> >>
> >> From my reading of “Disk Basic Unravelled,” I see that one can load the
> >> filename at $094C and the file extension at $0954, then put the start
> >> address, end address and execute address on the stack, and finally call
> >> SAVEM at $CF7E. Yes, I know that is not the official entry point, I am
> >> bypassing the initial code to get the file name and addresses from the
> >> Basic input buffer.
> >>
> >> Here is the snippet of (brute force) code that I wrote:
> >>
> >> PSHS CC,A,B,DP,X,Y,U SAVE ALL JUST IN CASE
> >> LDX #$094C
> >> LDA #$53 S
> >> STA ,X+
> >> LDA #$43 C
> >> STA ,X+
> >> LDA #$52 R
> >> STA ,X+
> >> LDA #$4E N
> >> STA ,X+
> >> LDA #$31 1
> >> STA ,X+
> >> LDA #$54 T
> >> STA ,X+
> >> LDA #$4F O
> >> STA ,X+
> >> LDA #$38 8
> >> STA ,X
> >> LDX #$0954
> >> LDA #$42 B
> >> STA ,X+
> >> LDA #$49 I
> >> STA ,X+
> >> LDA #$4E N
> >> STA ,X
> >> LDD #$2382 START SCR 1
> >> PSHS A,B
> >> LDD #$439F END SCR 8
> >> PSHS A,B
> >> LDD #$0000 EXEC
> >> PSHS A,B
> >> JSR $CF7E SAVEM
> >> PULS U,Y,X,DP,B,A,CC RESTORE ALL
> >>
> >> What I am concerned about is whether or not I am getting the addresses
> >> onto the stack in the right order, and with the correct byte order.
> >>
> >> The reason I’m asking is that this code “kind of works” in my Color
> >> Forth. I do get a file onto disk called SCRN1TO8.BIN, but it is 21
> blocks
> >> long, instead of 4 blocks, like I expected.
> >>
> >> Finally, while my Drivewire UI shows the disk activity start and end, my
> >> code does not return to the command line in Color Forth, so I am also
> >> concerned about that. I see in the “Disk Basic Unravelled” that the
> SAVEM
> >> command dose end with an RTS, so I did expect my code to return.
> >>
> >> Thanks very much, in advance, for any comments or advice you may offer!
> >>
> >> smp
> >> --
> >> Stephen M. Pereira
> >> Bedford, NH 03110
> >> KB1SXE
> >>
> >>
> >>
> >> --
> >> Coco mailing list
> >> Coco at maltedmedia.com
> >> https://pairlist5.pair.net/mailman/listinfo/coco
> >>
> >
> > --
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>
>
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