/ 
CPU-Z80-Assembler-2.05_05
River stage one • 1 direct dependent • 1 total dependent
/ CPU::Z80::Assembler

NAME

CPU::Z80::Assembler - a Z80 assembler

SYNOPSIS

use CPU::Z80::Assembler;

$CPU::Z80::Assembler::verbose = 1;
$binary = z80asm(q{
    ORG 0x1000
    LD A, 1
    ...
});
$binary = z80asm(@lines);
$binary = z80asm('#include <file.asm>');
open($fh, $file); $binary = z80asm(sub {<$fh>});

DESCRIPTION

This module provides a single subroutine which implements a Z80 assembler.

EXPORTS

By default the 'z80asm' subroutine is exported.

FUNCTIONS

z80asm

This takes as parameter a list of either text lines to parse, or iterators that return text lines to parse.

The list is passed to the CPU::Z80::Preprocessor that takes care of file includes and handles the %line and #line lines generated by external preprocessors like cpp or nasm. The result of this stage is a CPU::Z80::Assembler::Stream of CPU::Z80::Assembler::Line objects.

This stream of lines is passed on to the CPU::Z80::Assembler::Lexer to scan the input and return a CPU::Z80::Assembler::Stream of CPU::Z80::Assembler::Token objects.

The stream of tokens is passed on to CPU:Z80::Assembler::Parser that parses the input and generates the object image in CPU::Z80::Assembler::Program. Assembly macro expansion is handled at this stage by CPU::Z80::Assembler::Macro.

The assembly program is composed by a list of CPU::Z80::Assembler::Segment, each representing one named section of code. Each segment is composed by a list of CPU::Z80::Assembler::Opcode, each representing one assembly instruction.

The output object code is returned as a string.

If the $CPU::Z80::Assembler::verbose variable is set, an output listing is generated by CPU::Z80::Assembler::List on standard output.

Assembly is done in four steps:

  1. input is preprocessed, scanned and split into tokens

  2. tokens are parsed and converted to lists of opcodes

  3. addresses for each opcode are allocated

  4. object code is generated for each opcode, computing all expressions used; the expressions are represented by CPU::Z80::Assembler::Expr.

The z80masm program (installed as part of this module) calls the z80asm() function to assemble an input source file, generate an output binary file, and produce an assembly listing on standard output.

SYNTAX

Instructions are separated by new lines or colons ':', and have the following format, in ASCII. Comments start with ';'. Lines starting with '#' are ignored, to handle files generated by pre-processors.

; comment beginning with ;
# comment beginning with # as first char on a line
[LABEL [:]] INSTRUCTION [: INSTRUCTION ...] [; optional comments]
LABEL [:]
LABEL = EXPRFESSION [; ...]

See CPU::Z80::Assembler::Lexer for details on the allowed source file tokens.

Numbers

Numbers can be supplied in either decimal, hexadecimal, or binary. Numbers must start with a digit 0 to 9. Hex numbers have a leading 0x (0x****) or a trailing H (0****H). Binary numbers have a leading 0b (0b****) or a trailing B (****B).

Pseudo-instructions

DEFB 0x12

A byte of data

DEFW 0x1234

A 16-bit word of data, in little-endian order. So the example would actually insert 0x34 followed by 0x12.

DEFT "literal text", 0x00

A literal string, either single- or double-quoted. Can optionally be followed by a comma-seperated list of bytes. Quoted text can not include the quotes surrounding it or newlines.

ORG 0x4567

Tell the assembler to start building the code at this address. Must be the first instruction and can only appear once. If absent, defaults to 0x0000. This value is available in an assembler label called 'org'.

INCLUDE "filename"

Recursively include another file at the current source file.

Mnemonics

Standard Z80 mnemonics as well as the "unofficial" Z80 instructions are supported.

RST vectors

The RST instruction takes as its parameter either the address to jump to or the reset vector number - this is just the address / 8.

This means that, for example, RST 0x28 == RST 5.

DJNZ and JR

The DJNZ and JR instructions take an address as their destination, not an offset. If you need to use an offset, do sums on $. Note that $ is the address of the *current* instruction. The offset needs to be calculated from the address of the *next* instruction, which for these instructions is always $ + 2.

STOP

This extra instruction (which assembles to 0xDD 0xDD 0x00) is provided for the convenience of those using the CPU::Emulator::Z80 module.

Labels

Labels may be preceded by a dollar sign '$', must start with a letter or underscore, and consist solely of letters, underscores and numbers. They default to having the value of the address they are created at. If you want to assign another value, then you can say:

label = 0x1234

You can use $ to refer to the current address. Mathemagical operations are allowed too - the value is parsed as perl, and you can refer to other labels as their name:

label      = $ + 8
otherlabel = label / 2 + 3

Macros

Macros are supported. See CPU::Z80::Assembler::Macro for details.

BUGS and FEEDBACK

We welcome feedback about our code, including constructive criticism. Bug reports should be made using http://rt.cpan.org/.

SEE ALSO

CPU::Z80::Assembler::Lexer CPU::Z80::Assembler::Macro CPU::Z80::Assembler::Parser CPU::Emulator::Z80

AUTHORS, COPYRIGHT and LICENCE

Copyright (c) 2008-2009, David Cantrell <david@cantrell.org.uk>, Paulo Custodio <pscust@cpan.org>

This software is free-as-in-speech software, and may be used, distributed, and modified under the terms of either the GNU General Public Licence version 2 or the Artistic Licence. It's up to you which one you use. The full text of the licences can be found in the files GPL2.txt and ARTISTIC.txt, respectively.

CONSPIRACY

This software is also free-as-in-mason.