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190 lines
7.3 KiB
Markdown
190 lines
7.3 KiB
Markdown
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# DeskTop diassembly notes
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## DESKTOP.SYSTEM
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A short (8k) loader program. This is likely responsible for copying
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the rest to a RAM card (if available), then invoking the main app.
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## DESKTOP2.$F1
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This is large - 111k. It includes a loader, the DeskTop app (with both
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main memory and aux memory segments, filling everything from $4000 to
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$FFFF (except for I/O space and ProDOS), and still having more code
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segments swapped in dynamically.
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The file is broken down into multiple segments:
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* segment 0: load - A$2000-$257F, L$0580, mark $000000 (Loader)
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* segment 1: aux - A$4000-$BFFF, L$8000, mark $000580 (MGTK, DeskTop)
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* segment 2: auxlc - A$D000-$ECFF, L$1D00, mark $008580 (DeskTop)
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* segment 3: auxlc - A$FB00-$FFFF, L$0500, mark $00A280 (DeskTop)
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* segment 4: main - A$4000-$BEFF, L$7F00, mark $00A780 (DeskTop)
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* segment 5: main - A$0800-$0FFF, L$0800, mark $012680 (Initializer)
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* segment 6: main - A$0290-$03EF, L$0160, mark $012E80 (Invoker)
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* segments dynamically loaded for these actions:
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* disk copy - A$0800, L$0200, mark $012FE0
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* format/erase - A$0800, L$1400, mark $0160E0
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* selector - A$9000, L$1000, mark $0174E0
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* common - A$5000, L$2000, mark $0184E0 (used by selector, copy, delete)
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* file copy - A$7000, L$0800, mark $01A4E0
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* file delete - A$7000, L$0800, mark $01ACE0
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* selector - A$7000, L$0800, mark $01B4E0
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* (EOF is $01BCE0)
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The DeskTop segments loaded into the Aux bank switched ("language
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card") memory can be used from both main and aux, so contain relay
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routines, resources, and buffers. More details below.
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## Structure
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### Loader
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`loader.s`
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Invoked at $2000; patches the ProDOS QUIT routine (at LC2 $D100) then
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invokes it. That gets copied to $1000-$11FF and run by ProDOS.
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The invoked code stashes the current prefix and re-patches ProDOS with
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itself. It then (in a convoluted way) loads in the second $200 bytes of
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`DESKTOP2` at $2000 and invokes that.
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This code then loads the rest of the file as a sequence of segments,
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moving them to the appropriate destination in aux/banked/main memory.
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There's fourth chunk of code, which expects to live at $280 so it
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can't co-exist with the Invoker; it may be temporary code, as there is
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no sign that it is ever moved into place. It's also unclear how it
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would be hooked in. The routine detects OA+CA+P and prints the DHR
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screen to an ImageWriter II printer attached to Slot 1. (This may have
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been used to produce screenshots during development for manuals.)
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### Invoker
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`invoker.s`
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Loaded at $290-$03EF, this small routine is used to invoke a target,
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e.g. a double-clicked file. System files are loaded/run at $2000,
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binary files at the location specified by their aux type, and BASIC
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files loaded by searching for BASIC.SYSTEM and running it with the
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pathname passed at $2006 (see ProDOS TLM).
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### Initializer
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`desktop.s`
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Loaded at $800-$FFF, this does one-time initialization of the
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DeskTop. It is later overwritten when any desk accessories are
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run.
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### Mouse Graphics Tool Kit (MGTK)
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`a2d.s`
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AUX $4000-$851E is the GUI library used for the DeskTop application
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and (presumably) for disk copy and Selector apps (TBD).
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Entry point is $4000 with a ProDOS MLI-style calling convention
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### "DeskTop" Application
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`desktop.s`
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DeskTop application code is in the lower 48k of both Aux and Main:
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* Aux $851F-$BFFF - sitting above the GUI library
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* Main $4000-$BEFF
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...and in the Aux language card area (accessible from both aux and
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main code) are relays, buffers and resources:
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* Aux $D000-$ECFF - relays and other aux/main helpers, resources (menus, strings, window)
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* Aux $ED00-$FAFF - hole for data buffer
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* Aux $FB00-$FFFF - more resources (file types, icons)
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($C000-$CFFF is reserved for I/O, and main $BF page and language card is ProDOS)
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Interactive commands including disk copy/format/erase, file
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copy/delete, and Selector add/edit/delete/run all dynamically load
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main memory code segments into one or more of: $800-$1FFF,
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$5000-$6FFF, $7000-$77FF, and $9000-$9FFF. When complete, any original
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code above $4000 is reloaded.
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```
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Main Aux ROM
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$FFFF +-------------+ +-------------+ +-------------+
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| ProDOS | | DeskTop | | Monitor |
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$F800 | | | Resources/ | +-------------+
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| | | Buffers | | Applesoft |
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$D000 +-------------+ +-------------+ +-------------+ +-------------+
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| I/O |
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$C000 +-------------+ +-------------+ +-------------+
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| ProDOS GP | | DeskTop |
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$BF00 +-------------+ | App Code |
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| DeskTop | | |
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| App Code | | |
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$A000 | +------+ | |
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| | Seg | | |
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$9000 | +------+ | |
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$8800 | | | Font |
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$851F | | +-------------+
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| | | MGTK |
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$7800 | +------+ | |
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| | Seg | | |
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$7000 | +------+ | |
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| | Seg | | |
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$5000 | +------+ | |
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$4000 +-------------+ +-------------+
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| Graphics | | Graphics |
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$2000 +-------------+ +-------------+
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| Initializer | | Desk Acc |
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| & Desk Acc | | |
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| & Segments | | |
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$0800 +-------------+ +-------------+
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| Text | | Text |
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$0400 +-------------+ +-------------+
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| Invoker | | |
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$0300 +-------------+ +-------------+
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| Input Buf | | Input Buf |
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$0200 +-------------+ +-------------+
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| Stack | | Stack |
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$0100 +-------------+ +-------------+
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| Zero Page | | Zero Page |
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$0000 +-------------+ +-------------+
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```
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