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144 lines
5.4 KiB
Markdown
144 lines
5.4 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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probably the disk copy code which is swapped in dynamically.
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The file is broken down into multiple segments:
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* segment 0: load - address $2000-$257F, length $0580, file offset $000000 (Loader)
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* segment 1: aux1 - address $4000-$BFFF, length $8000, file offset $000580 (A2D, part of DeskTop)
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* segment 2: aux2 - address $D000-$ECFF, length $1D00, file offset $008580 (More of DeskTop)
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* segment 3: aux3 - address $FB00-$FFFF, length $0500, file offset $00A280 (More of DeskTop)
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* segment 4: main - address $4000-$BEFF, length $7F00, file offset $00A780 (More of DeskTop)
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* segment 5: main - address $0800-$0FFF, length $0800, file offset $012680 (???)
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* segment 6: main - address $0290-$03EF, length $0160, file offset $012E80 (Invoker)
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* segment N: _TBD_ - 38k so must be further subdivided. Disk Copy???
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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; it's unclear where that ends up or how
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it is invoked, but it appears to handle an OpenApple+ClosedApple+P
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key sequence and invoke slot one code - possibly debugging support?
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### Invoker
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`s6.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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### GUI Library "A2D"
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`a2d.s`
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AUX $4000-$8DFF 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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* Font is at $8800
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* Part of $8500-$87FF looks like part of "DeskTop" (see below), dealing with online volumes.
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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 $8E00-$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 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 $BF page and language card is ProDOS)
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```
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Main Aux ROM
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$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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$C000 +------------+ +------------+ +------------+
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| ProDOS | | DeskTop |
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$BF00 +------------+ | App Code |
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| DeskTop | | |
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| App Code | | |
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$8E00 | | +------------+
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| | | A2D GUI |
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| | | Library |
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$4000 +------------+ +------------+
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| Graphics | | Graphics |
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$2000 +------------+ +------------+
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| Init & | | Desk Acc |
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| Desk Acc | | |
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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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