mirror of
https://github.com/irmen/prog8.git
synced 2024-11-20 03:32:05 +00:00
86 lines
4.0 KiB
ReStructuredText
86 lines
4.0 KiB
ReStructuredText
|
|
.. _portingguide:
|
|
|
|
=============
|
|
Porting Guide
|
|
=============
|
|
|
|
Here is a guide for porting Prog8 to other compilation targets.
|
|
Answers to the questions below are used to configure the new target and supporting libraries.
|
|
|
|
.. note::
|
|
The assembly code that prog8 generates is not suitable to be put into ROM. (It contains
|
|
embedded variables, and self-modifying code).
|
|
If the target system is designed to run programs from ROM, and has just a little bit of RAM
|
|
intended for variables, prog8 is likely not a feasible language for such a system right now.
|
|
|
|
|
|
CPU
|
|
---
|
|
#. 6502 or 65C02? (or strictly compatible with one of these)
|
|
#. can the **64tass** cross assembler create programs for the system? (if not, bad luck atm)
|
|
|
|
Memory Map
|
|
----------
|
|
|
|
Zeropage
|
|
========
|
|
#. *Absolute requirement:* Provide three times 2 consecutive bytes (i.e. three 16-bit pointers) in the zeropage that are free to use at all times.
|
|
#. Provide list of any additional free zeropage locations for a normal running system (BASIC + Kernal enabled)
|
|
#. Provide list of any additional free zeropage locations when BASIC is off, but floating point routines should still work
|
|
#. Provide list of any additional free zeropage locations when only the Kernal remains enabled
|
|
|
|
Only the three 16-bit pointers are absolutely required to be able to use prog8 on the system.
|
|
But more known available zeropage locations mean smaller and faster programs.
|
|
|
|
|
|
RAM, ROM, I/O
|
|
=============
|
|
|
|
#. what part(s) of the address space is RAM? What parts of the RAM can be used by user programs?
|
|
#. what is the usual starting memory address of programs?
|
|
#. what part(s) of the address space is ROM?
|
|
#. what part(s) of the address space is memory mapped I/O registers?
|
|
#. is there a block of "high ram" available (ram that is not the main ram used to load programs in) that could be used for variables?
|
|
#. is there a banking system? How does it work (how do you select Ram/Rom banks)? How is the default bank configuration set?
|
|
Note that prog8 itself has no notion of banking, but this knowledge may be required for proper system initialization.
|
|
|
|
Character encodings
|
|
-------------------
|
|
#. if not PETSCII or CBM screencodes: provide the primary character encoding table that the system uses (i.e. how is text represented in memory)
|
|
#. provide alternate character encodings (if any)
|
|
#. what are the system's standard character screen dimensions?
|
|
#. is there a screen character matrix directly accessible in Ram? What's it address? Same for color attributes if any.
|
|
|
|
|
|
ROM routines
|
|
------------
|
|
#. provide a list of the core ROM routines on the system, with names, addresses, and call signatures.
|
|
|
|
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)
|
|
Routines to initialize the system to a sane state and to do a warm reset are useful too.
|
|
The more the merrier.
|
|
|
|
Floating point
|
|
==============
|
|
Prog8 can support floating point math *if* the target system has floating point math routines in ROM. If that is the case:
|
|
|
|
#. what is the binary representation format of the floating point numbers? (how many bytes, how the bits are set up)
|
|
#. what are the valid minimum negative and maximum positive floating point values?
|
|
#. provide a list of the floating point math routines in ROM: name, address, call signature.
|
|
|
|
|
|
Support libraries
|
|
-----------------
|
|
The most important libraries are ``syslib`` and ``textio``.
|
|
``syslib`` *has* to provide several system level functions such as how to initialize the machine to a sane state,
|
|
and how to warm reset it, etc.
|
|
``textio`` contains the text output and input routines, it's very welcome if they are implemented also for
|
|
the new target system. But not required.
|
|
|
|
There are several other support libraries that you may want to port (``diskio``, ``graphics`` to name a few).
|
|
|
|
Also of course if there are unique things available on the new target system, don't hesitate to provide
|
|
extensions to the ``syslib`` or perhaps a new special custom library altogether.
|
|
|