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81 lines
3.5 KiB
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81 lines
3.5 KiB
ReStructuredText
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.. _portingguide:
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=============
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Porting Guide
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=============
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Here is a guide for porting Prog8 to other compilation targets.
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Answers to the questions below are used to configure the new target and supporting libraries.
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CPU
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---
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#. 6502 or 65C02? (or strictly compatible with one of these)
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#. can the **64tass** cross assembler create programs for the system? (if not, bad luck atm)
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Memory Map
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----------
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Zero page
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=========
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#. *Absolute requirement:* Provide three times 2 consecutive bytes (i.e. three 16-bit pointers) in the Zero page that are free to use at all times.
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#. Provide list of any additional free Zero page locations for a normal running system (basic + kernal enabled)
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#. Provide list of any additional free Zero page locations when basic is off, but floating point routines should still work
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#. Provide list of any additional free Zero page locations when only the kernal remains enabled
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Only the three 16-bit pointers are absolutely required to be able to use prog8 on the system.
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But more known available Zero page locations mean smaller and faster programs.
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RAM, ROM, I/O
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=============
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#. what part(s) of the address space is RAM? What parts of the RAM can be used by user programs?
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#. what is the usual starting memory address of programs?
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#. what is the best place to put 2 pages (512 bytes total) of scratch area data in RAM?
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#. what part(s) of the address space is ROM?
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#. what part(s) of the address space is memory mapped I/O registers?
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#. is there a banking system? How does it work (how do you select Ram/Rom banks)? How is the default bank configuration set?
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Character encodings
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-------------------
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#. if not Petscii or CBM screencodes: provide the primary character encoding table that the system uses (i.e. how is text represented in memory)
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#. provide alternate character encodings (if any)
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#. what are the system's standard character screen dimensions?
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#. is there a screen character matrix directly accessible in Ram? What's it address? Same for color attributes if any.
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ROM routines
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------------
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#. provide a list of the core ROM routines on the system, with names, addresses, and call signatures.
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Ideally there are at least some routines to manipulate the screen and get some user input (clear, print text, print numbers, input strings from the keyboard)
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Routines to initialize the system to a sane state and to do a warm reset are useful too.
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The more the merrier.
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Floating point
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==============
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Prog8 supports floating point math *if* the target system has floating point math routines in ROM.
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If the machine has this:
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#. what is the binary representation format of the floating point numbers? (how many bytes, how the bits are set up)
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#. what are the valid minimum negative and maximum positive floating point values?
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#. provide a list of the floating point math routines in ROM: name, address, call signature.
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Support libraries
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-----------------
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The most important libraries are ``syslib`` and ``textio``.
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``syslib`` *has* to provide several system level functions such as how to initialize the machine to a sane state,
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and how to warm reset it, etc.
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``textio`` contains the text output and input routines, it's very welcome if they are implemented also for
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the new target system.
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There are several other support libraries that you may want to port (``diskio``, ``graphics`` to name a few).
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Also of course if there are unique things available on the new target system, don't hesitate to provide
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extensions to the ``syslib`` or perhaps a new special custom library altogether.
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