ASM.EXE by Phil Ruston - A native Z80 assembler for FLOS

V0.01

Usage:

ASM source_filename %xxx %yyy

(%xxx %yyy etc are optional folder assignment environment variables. These allow the assembler to look in folders outside the current directory for any included files.)

A binary file is produced with the same filename but with extension ".exe"


Directives supported:

• ORG - set code assembly location
• INCLUDE - include a source file at current location
• INCBIN - include a binary file at current location
• DB - data byte(s) EG: 'DB 1,2,3,some_symbol' , 'DB "string1"' or mixed
• DW - data word(s)
• DS - data string (EG: "DS 10,5" (enters 10 bytes, each with value 5))
• EQU - set value of a symbol, (EG: "my_symbol equ $1234")

General:

• Only the official Z80 opcodes are currently allowed.
• There are no macros or conditional assembly directives.
• Line labels must be aligned to the left margin
• A tab or space must exist before opcodes or instructions such as INCBIN, ORG etc.
• Comments should begin with a semi-colon
• Lines can be a maximum of 255 characters long

Numbers/Maths/expressions:

• Operators supported: "+", "-", "/", "*", ">>", "<<", "&" (and), "|" (or)
• Bases: Unprefixed figure = decimal, $value = hex, %value = binary, quoted "n" or 'n' = ASCII
• "$" (alone) = Special case: Current opcode address, allowing "$+2", "$-2" etc references.
• (Page alignment can be achieved with org $+255&$ff00)
• The maths system internally uses 16-bit integers, therefore no part of an expression can be greater than 65535. 8-bit values derived from 16-bit can be in range -128 to 255) without returning errors.
• A sign prefix can be specified: EG "+1", "-5"
• Brackets can be used in expressions. The assembler scans the expression left to right solving the first innermost bracketed section it finds, until all bracketed sections have been resolved.

Labels / Symbols / Strings

• ORG using symbols: The symbol cannot be a forward reference (IE: Must be defined prior to the ORG directive.)
• ORG cannot specify an address lower than the current assembly location. If no ORG exists, assembly starts at 0.
• Instructions/symbols/etc are NOT case sensitive
• Includes can be nested, to a maximum of 8 levels
• Line labels can end in colons if desired (will be ignored)
• Symbol table is limited to approx 32KB max.
• When using strings with DB directive, the quote character (CHR $22) cannot be within the string, it must be declared separately as a byte: EG: DB $22,"Hello",$22," said Bob." (Apostropes (') can be within strings.)
• All symbols/labels are global.

Files:

• There is no restriction on the length of source .asm files
• Max incbin filesize = 64KB
• Output file starts from the lowest defined address (where data has been placed) 64KB max.
• No paths permitted in filenames however, the directories that should be scanned for component files can be specified on the command line via FLOS directory assignments, EG: "ASM MY_PROJ.ASM %INC %DAT"
• Any quotes around filenames are ignored (spaces are not allowed in filenames)

To do:

• More instruction syntax checking is required (extraneous args, illegal arg combinations etc.)
• Optimization for speed and code size.