Ultimate Basic v1.5.7

Ultimate Basic v1.5.7 – Release Notes

2026-09-21 – Tracker tunes and an inline-assembler fix

New language elements

• Added tune ... end: describe a 3-voice SID tracker tune (instruments,
  order list, per-voice pattern rows such as "C-4 01 V24") directly in the
  source. The compiler builds a self-contained, zero-page-free player at
  compile time and defines sid_init / sid_play, so music play|stop| pause|resume work exactly as with load sid. Vibrato, slide, note cut
  and speed change are supported. tune at $addr moves the blob (default
  $8000). This is what the Visual Assembler SID editor's "Export to
  UltimateBasic" now generates.

Fixes

• Inline asm { }: label,X, label,Y and JMP (label) were assembled
  as plain absolute instructions (the index/indirect mode was dropped), so
  table lookups such as LDA table,X read the wrong byte. The addressing
  mode is now kept.
• music play: the CIA1 IRQ wrapper acknowledged the timer by WRITING $01 to
  $DC0D, which clears the interrupt mask, so the music IRQ stopped after the
  first tick. It now acknowledges by reading $DC0D.

2026-09-21 – Custom charsets, code layout and non-blocking sound

New language elements

• Added charset on / charset off. charset addr (default $3800) used to
  only set the destination of chardef; charset on now points the VIC-II
  at that RAM set (read-modify-write of $D018 bits 1-3, the screen-matrix
  bits are kept) and charset off restores the ROM set ($1000, or $1800
  after lowercase). The base must be a multiple of $800 inside VIC bank 0.
• Added a build-time check that generated code does not overlap the charset:
  charset on claims the 2 KB set and every chardef its 8 bytes; a
  program that reaches into them stops with "the program code (...)
  overlaps the charset area ...". Data in an org gap is not counted.
• Added org addr. Placed between sub/fn definitions it continues the
  subroutine code at addr and zero-fills the gap, which stays free for
  data (fonts, sprites, tables). Subs never fall through, so this is safe;
  org below the current code end is an error.
• Extended incbin with incbin "file", addr, skip [, len]: skip a header
  (e.g. a .prg load address) and/or take only a slice. incbin ..., addr can
  now be written into an org gap.
• Added sfx channel, freq, frames [, wave]: a non-blocking SID note. It
  sets attack 0 / sustain 0 / release 0 and picks the decay from frames
  (1 frame = 20 ms) at compile time, re-triggers the voice and returns at
  once. wave is 16 (triangle), 32 (saw, default), 64 (pulse) or 128
  (noise). Unlike sound it is safe inside a game loop.

Fixes

• sound waited on raster line 0, which $D012 (low 8 bits) shows twice per
  frame (lines 0 and 256), so notes were half as long as requested; two of
  its branches were also patched over their opcode, crashing the program
  for any non-zero duration. It now waits on raster line 200 like delay.
• word assignments computed products in 8 bits: w += 300 * level,
  w = w + 100 * level and w = 100 * level + 900 now keep all 16 bits.
• print a / 10 (and other arithmetic on a float) printed the raw Q8.8
  value as an integer; it now prints N.DD.
• Arrays are zeroed once at program start (RAM contents at power-up are
  random; array(N) previously started with whatever was there).
• Running out of permanent zero page ($02-$4F) is now a compile-time
  error ("out of zero page"). Before, variables and for limit/step
  bytes silently spilled into the scratch area and broke loops. Sequential
  for loops now release their two limit/step bytes when the loop ends
  (if the body declared no variables), so many loops no longer exhaust it.
• Manual corrections: % binary literals were documented but never
  supported by the lexer (use $hex or decimal); the charset example used
  the $D018 value of another address ($1E selects $3800, $1A selects $2800).
• Tests: a missing ROL zp opcode in the test CPU was added, and the koala
  tests no longer race on a shared temp file.