Groups > comp.sys.apple2.programmer > #6082

Re: Typo in ProDOS refTechMan

From	Jerry Penner <jerry+a2@jpen.ca>
Newsgroups	comp.sys.apple2.programmer
Subject	Re: Typo in ProDOS refTechMan
Date	2023-08-24 00:06 -0600
Organization	A noiseless patient Spider
Message-ID	<yubr0ntht3u.fsf@jpen.ca> (permalink)
References	<20230822221945.4eb8a091@laptop-sigfox> <yubzg2iicr9.fsf@jpen.ca> <20230823082311.3dc76fb1@laptop-sigfox> <uc4d2e$4ofj$1@solani.org> <20230823152214.5e86230e@laptop-sigfox>

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Colin Leroy-Mira <colin@colino.net> writes:

> Hi,
>
>> Oliver Schmidt <ol.sc@web.de> wrote:
>>I - pretty strongly - disagree. What JSR does is an implementation
>>detail. What the documentation wants to express is that MLI returns 3
>>bytes "behind" what a "bare" JSR returns to. Putting a 6 there instead
>>of a 3 is plainly wrong.
>
> I see what you mean, but the original phrasing is confusing. It could
> be "the MLI returns 3 bytes behind than a normal JSR does, to the
> address of the JSR plus 6".


The P8 tech-ref states:

----------------------------------------
SYSCALL  JSR MLI       ;Call Command Dispatcher
         DB CMDNUM     ;This determines which call is being made
         DW CMDLIST    ;A two-byte pointer to the parameter list
         BNE ERROR     ;Error if nonzero

      Upon completion of the call, the MLI returns to the address of the
      JSR plus 3 (in the above example, the BNE statement); the call
      number and parameter list pointer are skipped.
----------------------------------------

Where the CPU returns to is 6 bytes past the label SYSCALL, which is the
location of the "BNE ERROR" instruction.

I think I always read and understood the book the way I think Oliver
does, but I think the book's address arithmetic is wrong, looking at it
now.

-- 
--
Jerry     jerry+a2 at jpen.ca

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Thread

Typo in ProDOS refTechMan Colin Leroy-Mira <colin@colino.net> - 2023-08-22 22:19 +0200
  Re: Typo in ProDOS refTechMan Jerry Penner <jerry+a2@jpen.ca> - 2023-08-22 22:49 -0600
    Re: Typo in ProDOS refTechMan Colin Leroy-Mira <colin@colino.net> - 2023-08-23 08:23 +0200
      Re: Typo in ProDOS refTechMan Oliver Schmidt <ol.sc@web.de> - 2023-08-23 07:38 +0000
        Re: Typo in ProDOS refTechMan Colin Leroy-Mira <colin@colino.net> - 2023-08-23 15:22 +0200
          Re: Typo in ProDOS refTechMan Jerry Penner <jerry+a2@jpen.ca> - 2023-08-24 00:06 -0600
            Re: Typo in ProDOS refTechMan Jeff Blakeney <CUTjeffrey_blakeney@yahoo.ca> - 2023-08-24 08:10 -0400
              Re: Typo in ProDOS refTechMan Michael J. Mahon <mjmahon@aol.com> - 2023-08-28 06:45 +0000
                Re: Typo in ProDOS refTechMan Jeff Blakeney <CUTjeffrey_blakeney@yahoo.ca> - 2023-08-28 08:28 -0400
                Re: Typo in ProDOS refTechMan Michael J. Mahon <mjmahon@aol.com> - 2023-08-31 18:54 +0000
                Re: Typo in ProDOS refTechMan Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2023-08-31 13:30 +1000
                Re: Typo in ProDOS refTechMan Michael J. Mahon <mjmahon@aol.com> - 2023-08-31 18:54 +0000
                Re: Typo in ProDOS refTechMan Antoine Vignau <ntn.vignau@gmail.com> - 2023-09-07 12:41 -0700
                Re: Typo in ProDOS refTechMan Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2023-09-05 12:14 +1000
  Re: Typo in ProDOS refTechMan qkumba <peter.ferrie@gmail.com> - 2023-08-28 10:23 -0700
    Re: Typo in ProDOS refTechMan Antoine Vignau <ntn.vignau@gmail.com> - 2023-08-28 12:29 -0700

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