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gbhw.fs (lib)

The gbhw.fs library contains data to help using the Game Boy hardware.

Register addresses

Registers are simple constants that are prefixed with r. For example, rDIV is the divider register, and rSCY the window scroll-y register.

Using these constants from any context simply returns the numeric value of the address:

: reset-scroll
  0 rSCX c!
  0 rSCY c! ;

Register references (ASM)

All the register addresses are also available as references for assembly code. They have the same name, but are wrapped in square brackets ([r...]):

code reset-scroll
  0 # A ld,
  A [rSCX] ld,
  A [rSCY] ld,

Memory addresses

Special memory addresses are listed as constants prefixed with _. For example, _CARTRAM is the start of the cartridge RAM area, and _AUD3WAVERAM the start of the memory containing the wave samples for audio channel 3.

Flag bitmasks

Flags are simple constants that can be useful when working with register values. They are prefixed with the register name (without the r), followed by F_. For example, STATF_BUSY and STATF_LYCF are flags used with the rSTAT register.

  [rSTAT] a ld,
  STATF_BUSY # A and,
#z until,

Other values

There are a few other useful values available, such as SCRN_X (the width of the screen in pixels). Refer to the lib/gbhw.fs source to see the list of all available constants.