rgbds —
object file format documentation
This is the description of the object files used by rgbasm(1)
and rgblink(1). Please, note that the specifications may
change. This toolchain is in development and new features may require adding
more information to the current format, or modifying some fields, which would
break compatibility with older versions.
The following types are used:
LONG is a 32‐bit integer stored in
little‐endian format (Intel). BYTE is an
8‐bit integer. STRING is a 0‐terminated
string of BYTE.
; Header
BYTE ID[4] ; "RGB6"
LONG NumberOfSymbols ; The number of symbols used in this file
LONG NumberOfSections ; The number of sections used in this file
; Symbols
REPT NumberOfSymbols ; Number of symbols defined in this object file.
STRING Name ; The name of this symbol. Local symbols are stored
; as "Scope.Symbol".
BYTE Type ; 0 = LOCAL symbol only used in this file.
; 1 = IMPORT this symbol from elsewhere
; 2 = EXPORT this symbol to other objects.
IF Type != 1 ; If symbol is defined in this object file.
STRING FileName ; File where the symbol is defined.
LONG LineNum ; Line number in the file where the symbol is defined.
LONG SectionID ; The section number (of this object file) in which
; this symbol is defined. If it doesn't belong to any
; specific section (like a constant), this field has
; the value -1.
LONG Value ; The symbols value. It's the offset into that
; symbol's section.
ENDC
ENDR
; Sections
REPT NumberOfSections
STRING Name ; Name of the section
LONG Size ; Size in bytes of this section
BYTE Type ; 0 = WRAM0
; 1 = VRAM
; 2 = ROMX
; 3 = ROM0
; 4 = HRAM
; 5 = WRAMX
; 6 = SRAM
; 7 = OAM
LONG Org ; Address to fix this section at. -1 if the linker should
; decide (floating address).
LONG Bank ; Bank to load this section into. -1 if the linker should
; decide (floating bank). This field is only valid for ROMX,
; VRAM, WRAMX and SRAM sections.
LONG Align ; Alignment of this section (expressed as number of low bits
; to leave as 0). -1 if not defined.
IF (Type == ROMX) || (Type == ROM0) ; Sections that can contain data.
BYTE Data[Size] ; Raw data of the section.
LONG NumberOfPatches ; Number of patches to apply.
; These types of sections may have patches
REPT NumberOfPatches
STRING SourceFile ; Name of the source file (for printing error
; messages).
LONG Line ; The line of the source file.
LONG Offset ; Offset into the section where patch should
; be applied (in bytes).
BYTE Type ; 0 = BYTE patch.
; 1 = little endian WORD patch.
; 2 = little endian LONG patch.
; 3 = JR offset value BYTE patch.
LONG RPNSize ; Size of the buffer with the RPN.
; expression.
BYTE RPN[RPNSize] ; RPN expression. Definition below.
ENDR
ENDC
ENDR
Expressions in the object file are stored as RPN. This is an expression of the
form “2 5 +”. This will first push the value “2”
to the stack. Then “5”. The “+” operator pops two
arguments from the stack, adds them, and then pushes the result on the stack,
effectively replacing the two top arguments with their sum. In the RGB format,
RPN expressions are stored as BYTEs with some bytes being special prefixes for
integers and symbols.
rgbds was originally written by Carsten Sørensen
as part of the ASMotor package, and was later packaged in RGBDS by Justin
Lloyd. It is now maintained by a number of contributors at
https://github.com/rednex/rgbds.