millfork/docs/api/custom-platform.md

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Adding a custom platform

Every platform is defined in an .ini file with an appropriate name.

[compilation] section

• arch – CPU architecture. It defines which instructions are available. Available values:

  • nmos (original 6502)

  • strict (NMOS without illegal instructions)

  • ricoh (Ricoh 2A03/2A07, NMOS without decimal mode)

  • strictricoh (Ricoh 2A03/2A07 without illegal instructions)

  • cmos (WDC 65C02 or 65SC02)

  • 65ce02 (CSG 65CE02; experimental)

  • huc6280 (Hudson HuC6280; experimental)

  • 65816 (WDC 65816/65802; experimental; currently only programs that use only 16-bit addressing are supported)

  • z80 (Zilog Z80; experimental and slightly incomplete)

  • i8080 (Intel 8080; experimental, buggy and very incomplete)

  • gameboy (Sharp LR35902; experimental, buggy and very incomplete)

• encoding – default encoding for console I/O, one of ascii, pet/petscii, petscr/cbmscr, atascii, bbc, jis/jisx, apple2, iso_de, iso_no/iso_dk, iso_se/iso_fi, iso_yu. Default: ascii

• screen_encoding – default encoding for screencodes (literals with encoding specified as scr). Default: the same as encoding.

• modules – comma-separated list of modules that will be automatically imported

• other compilation options (they can be overridden using commandline options):

  • emit_illegals – whether the compiler should emit illegal instructions, default false

  • emit_cmos – whether the compiler should emit CMOS instructions, default is true on compatible processors and false elsewhere

  • emit_65816 – which 65816 instructions should the compiler emit, either no, emulation or native

  • decimal_mode – whether the compiler should emit decimal instructions, default is false on ricoh and strictricoh and true elsewhere; if disabled, a software decimal mode will be used

  • ro_arrays – whether the compiler should warn upon array writes, default is false

  • prevent_jmp_indirect_bug – whether the compiler should try to avoid the indirect JMP bug, default is false on 65C02-compatible or non-6502 processors and true elsewhere

  • compact_dispatch_params – whether parameter values in return dispatch statements may overlap other objects, default is true
    This may cause problems if the parameter table is stored next to a hardware register that has side effects when reading.

  • lunix – generate relocatable code for LUnix/LNG, default is false

  • zeropage_register – reserve a certain amount of bytes of zero page as a pseudoregister to increase language features. Default: 4 if targeting a 6502-based architecture, 0 otherwise.
    true is a synonym of the current compiler default (currently: 4) and false is a synonym for 0.

  • inline - inline functions automatically by default, default is false.

  • ipo - enable interprocedural optimization, default is false.

  • lenient_encoding - allow for automatic substitution of invalid characters in string literals using the default encodings, default is false.

  • use_shadow_registers_for_irq – use Z80 shadow registers in interrupt routines, default is true for Z80 and false otherwise

  • ix_stack – use the IX register to access stack variables, default is true for Z80 and false otherwise

  • iy_stack – use the IY register to access stack variables, default is false

  • ix_scratch – allow using the IY register for other purposes, default is false

  • iy_scratch – allow using the IY register for other purposes, default is false

  • output_intel_syntax – use Intel syntax instead of Zilog syntax, default is true for Intel 8080 and false otherwise

[define] section

This section defines values of features of the target. See the preprocessor documentation for more info.

[allocation] section

• zp_pointers – either a list of comma separated zeropage addresses that can be used by the program as zeropage pointers, or all for all. Each value should be the address of the first of two free bytes in the zeropage. Only used for 6502-based targets.

• segments – a comma-separated list of segment names.
  A segment named default is always required.
  Default: default. In all options below, NAME refers to a segment name.

• default_code_segment – the default segment for code and initialized arrays.
  Note that the default segment for uninitialized arrays and variables is always default.
  Default: default

• segment_NAME_start – the first address used for automatic allocation in the segment.
  Note that the default segment shouldn't start before $200, as the $0-$1FF range is reserved for the zeropage and the stack.
  The main function will be placed as close to the beginning of its segment as possible, but not necessarily at segment_NAME_start

• segment_NAME_end – the last address in the segment

• segment_NAME_codeend – the last address in the segment for code and initialized arrays.
  Only uninitialized variables are allowed between segment_NAME_codeend and segment_NAME_end.
  Default: the same as segment_NAME_end.

• segment_NAME_datastart – the first address used for non-zeropage variables, or after_code if the variables should be allocated after the code.
  Default: after_code.

[output] section

• style – how multi-segment programs should be output:

  • single – output a single file, based mostly, but not necessarily only on data in the default segment (the default)

  • lunix – like single, but add data necessary for relocation between code and data (requires lunix option in the compilation section)

  • per_segment – generate a separate file with each segment

• format – output file format; a comma-separated list of tokens:

  • literal byte values

  • startaddr – little-endian 16-bit address of the first used byte of the compiled output (not necessarily the segment start)

  • startpage – the high byte of startaddr

  • endaddr – little-endian 16-bit address of the last used byte of the compiled output (usually not the segment end)

  • allocated – all used bytes

  • pagecount – the number of pages used by all used bytes (including partially filled pages)

  • <addr>:<addr> - inclusive range of bytes

  • <segment>:<addr>:<addr> - inclusive range of bytes in a given segment

  • d88 - a D88 floppy disk image for PC-88

  • tap - a tape disk image for ZX Spectrum

• extension – target file extension, with or without the dot

• bbc_inf – should the .inf file with file metadata for BBC Micro be created