xkas-plus (v14+1)

This is a fork of xkas v14, because I like xkas v14 and wanted to touch it up a bit.

As with the original, this code is in the public domain.

What's new

• Ability to assemble directly to an IPS patch instead of a binary (with the -ips switch)

• New architecture options:

  • 6502 / nes.cpu - MOS 6502
  • 65c02 - WDC 65C02 (untested)
  • 65ce02 - CSG 65CE02 (untested)
  • huc6280 / pce.cpu / tg16.cpu - Hudson HuC6280 (untested)
  • spc700 / snes.smp - Sony SPC700
    • See test/test_spc.asm for syntax examples
  • 65816 - identical to snes.cpu

• Ability to export defines and labels to a separate file (with the -e filename switch)
  Supported output formats:

  • *.asm - assembly include
  • *.ram.nl - FCEUX debug symbols (labels only)
  • *.vs - VICE debug symbols (labels only)

• New directives (mostly for increased xkas v06 compatibility):

  • fillbyte / padbyte - specifies a default value for the fill, fillto, and align directives (these were originally two separate directives in v06, though I may make them distinct later)
  • pad - identical to fillto
  • table - allows you to specify a .tbl file to use for custom character encoding (up to four bytes per 8-bit character)
    • cleartable - restores the default encoding
  • warnpc - verifies that code is being assembled below a given address
  • bank - set current program bank (default 0)
  • banksize - set size of program banks (default/maximum $10000)
    • These two directives control the mapping between physical and logical addresses. For example:

    banksize $2000
    bank 0
    org $8000 // assembles to file offset $0000
    org $9000 // assembles to file offset $1000
    bank 1
    org $8000 // assembles to file offset $2000
    org $9000 // assembles to file offset $3000
    org $a000 // assembles to file offset $2000 (not $4000!)
    

    • Note that for 65816 / snes.cpu, the bank and banksize settings are only relevant when the standard lorom, hirom, etc. address mapping modes aren't in effect (so that you can work with less common addressing setups, like with the SA-1).

• Directives for 6502 / nes.cpu:

  • header / noheader - behave the same as their snes.cpu counterparts, but for a 16-byte iNES header instead of a 512-byte SNES copier header.
    • The default is noheader, so you can insert an iNES header manually before using the header directive for the actual ROM contents. The header directive does not generate an iNES header on its own.

• New directives for 65816 / snes.cpu:

  • exlorom / exhirom mapping modes

Goals

• Support for more architectures (SuperFX, GB/Z80, etc)
  • Support for undocumented 65xx opcodes
• Some useful system-specific directives for the above
• Actual documentation of the above
• Some other useful(?) directives, including from older xkas versions
• Macros (another lost feature of xkas v06)
  • not quite the highest priority

Why not bass?

bass was actually my original target for this project, but in using and modifying it I found a lot of bad flaws with the way bass parses code (think about the words "unintentionally significant whitespace" if you want an idea) that would have been a real pain to fix in an actually satisfactory way.

The table-based assembly in bass was an attractive feature that would have made it very simple to add support for most or all of the new architectures that I wanted, but the way it was implemented partially contributed to the above issue (and I don't know how well it would have worked for things like THUMB, which xkas v14 supports already, or pretty much any RISC architecture where opcodes and operands aren't byte-aligned).

Why not xkas v06?

(a.k.a. the version almost everyone actually uses)

v14's code is much cleaner and more easily extensible. That's more or less the only reason. Hopefully in re-adding some of v06's features I can bridge the gap a bit, but things like the new comment syntax will still keep it from being completely backwards compatible with v06.