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PostPosted: Sat May 23, 2020 11:53 am 
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Joined: Mon Sep 14, 2015 8:50 pm
Posts: 112
Location: Virginia USA
At the request of someone from another family of 6502-based computers (Atari) with a retro-fitted 65816 hardware enhancement, I searched for and found the source for the 16 bit operating system GSOS for the Apple IIGS:

https://archive.org/details/GSOS_6.0.1_source

If nothing else, it's a good resource for writing code for the 65816 in assembly language.

Cheers,
Andy


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PostPosted: Sat May 23, 2020 12:22 pm 
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Joined: Thu Dec 11, 2008 1:28 pm
Posts: 10985
Location: England
Oh yes, always good to see a big chunk of solid code. Here's a snippet from HS.FST.src indicating both a calling convention and a documentation convention:
Quote:
Code:
******************************************************************************
*
*    Name:   Appl_call
*
* Description:   Entry point for   all application   calls.   Called by GS/OS   only.
*      Validates call before passing control to call handler.
*
*     Created:   Oct 6, 1987
*    Modified:   Mar 5, 1991
*      Author:   Bryan Atsatt
*
*   Entry:   jml
*
*   Input:   A = undefined
*      X = call number   times 2
*      Y = class number times 2
*      P = nvmxdizc
*          ..000...
*
*      Output:   A = error code if carry   set
*      X = undefined
*      Y = undefined
*      P = nvmxdizc
*          ..000..1 = error
*            0 = no error
*
*    Exit:   jml sys_exit
*
*    Uses:   Everything!
*
******************************************************************************


and a simpler example:
Quote:
Code:
******************************************************************************
*
*    Name:   add_separator
*
* Description:   This routine will insert a class 0 or 1   separator at the
*      beginning of the gstring pointed to by X and Y.
*
*     Created:   Nov 6, 1987
*    Modified:   Nov 6, 1987
*      Author:   Bryan Atsatt
*
*   Entry:   jsr
*
*   Input:   A = undefined
*      X = low   byte of   pointer   to gstring
*      Y = high byte of pointer to gstring
*      P = nvmxdizc
*          ..000...
*      B = K
*
*      class         ;class of call.
*
*      Output:   A = undefined
*      X = undefined
*      Y = undefined
*      P = nvmxdizc
*          ..000...
*      B = K
*
*    Exit:   rts
*
*    Uses:   all registers
*      input_string
*      length
*
******************************************************************************


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