earasm

Installation

pip install ply

Running

python -m earasm input1.ear [ input2.ear ... ] output.peg

Assembler Syntax

Directives:

• .db 0xFA, 'A', 2 + 2 - 1; "string literal"
  • Defines one or more literal bytes
• .dw 0xF00D, @some_label
  • Defines one or more literal words (16-bit values)
• .lestring "string literal"
  • Defines a length-encoded string
• .export @<symname> [, "symbol name"]
  • Exports a symbol in the symbol table, optionally with a different symbol name than label name
• .loc <NEWPC> [, <NEWDPC>]
  • Redefines the assembler's assumed value of PC and optionally DPC
• .scope
  • Switches to a new scope for local labels (labels starting with @.)
• .segment @<segname>
  • Switches to the named segment

Instruction suffixes:

• F: Adds the TF (Toggle Flags) instruction prefix (e.g. MOVF)
• Y: Adds the TF instruction prefix if necessary to ensure that flags will be written (e.g. MOVY.EQ)
• N: Adds the TF instruction prefix if necessary to ensure that flags will NOT be writtne (e.g. INCN)
• .<condition code>: Sets the condition that must be met for the instruction to execute. Default is AL (always)

Automatic labels:

• @: Address of current position
• @@: Address of the start of the current segment
• @DPC@: Current DPC value used by the assembler
• @PC@: The value that PC will hold when this instruction executes, which points to the next code byte after this instruction
• @AFTER@: Address of the byte directly after the end of the current item
  • For instructions, this points to the byte directly after the last code byte in this instruction, which may be different than @PC@ when DPC != 0.
• @<segname>@: Address of the beginning of a segment (e.g. @TEXT@)

Segments:

• @TEXT: Default segment. Mapped as EAR_PROT_READ | EAR_PROT_EXECUTE at virtual address 0x0100.
• @DATA: Segment for writeable data. Mapped as EAR_PROT_READ | EAR_PROT_WRITE at the next page after @TEXT.

Entrypoint:

• @main: Name of symbol to export to define the entrypoint.

Comments:

• /* C style */
• // C++ style