A09 - 6809 / 6309 / 6800 Assembler

Copyright (c) 1993,1994 L.C. Benschop
Parts Copyright (c) 2001-2010 Hermann Seib

Based on Lennart Benschop's C core that can be found somewhere on the 'net (last address known to me was http://koti.mbnet.fi/~atjs/mc6809/Assembler/A09.c), I built a complete Macro Assembler that is functionally better than the TSC Flex9 Assembler (no wonder, I got multimegabytes to play with, whereas this excellent piece of software works within 50K or so!). It can deliver binary, Intel Hex, Motorola S1, and Flex9 binary output files, plus Flex9 RELASMB-compatible relocatable object modules.

I taylored the original to my taste by working through the source code; since A09 has reached a level of complexity that doesn't really lend itself to following the "Use the Source, Luke!" principle if you just want to hack a little 6809 assembly program, I've added this documentation. Have fun!

Hermann Seib, 2010

Syntax

a09 [-{b|r|s|x|f}[filename]]|[-c] [-l[filename]] [-ooption]* [-dsym=value]* sourcefile*

Command Line Parameters

-c

suppresses code output (corresponds to ASMB's B command line option)

-bfilename (default output mode)

create a binary output file
if no file name is given, the extension .bin is used (.b on Unix)

-rfilename

create a Flex9 RELASMB-compatible output file name
if no file name is given, the extension .rel is used

Attention: this file format is undocumented; my solution has been derived from some bits of information gathered on the Flex User Group mailing list and a bit of playing with the original. In my tests, the output was identical to RELASMB's; nevertheless, A09 might create modules that are incompatible with the original under circumstances that I don't know or haven't tested.

-sfilename

create a Motorola S-record output file name
if no file name is given, the extension .s09 is used

-xfilename

create an Intel hex output file name
if no file name is given, the extension .hex is used

-ffilename

create Flex9 ASMB-compatible output file
if no file name is given, the extension .bin is used

-lfilename

create a list file (default no listing)
if no file name is given, the extension .lst is used

-dsym[=value]

define a symbol (see TEXT directive below)
(roughly corresponds to ASMB's command line parameters 1-3)

-oopt

defines an option (see below)

sourcefile

the assembler source file(s) to be processed.
At least one source file must be given; the first one also defines the default output and listing file names.

Options

Over the years, A09 has learned quite a lot, and it can handle source files / list files in various formats. To allow their selection, I have expanded the scope of the OPT directive (see the FLEX9 Assembler Manual that can be found in the Documentation section on www.flexusergroup.com for details). Here's the list of additional options available in A09 (* denotes the default value for a mutually exclusive set):

Each of the above options has a corresponding text symbol that is set to 0 or 1, corresponding to the state of the option. This allows for conditional assembly, for example:

  IF &H63
    LDW  Data
    SUBW #12
    STW  Data
  ELSE
    PSHS D
    LDD  Data
    SUBD #12
    STD  Data
    PULS D
  ENDIF

Directives

A09 handles the full set of directives available in the FLEX9 ASMB and RELASMB programs (see the excellent Documentation section on www.flexusergroup.com for the manuals of these programs). Apart from these, it knows the following directives:

Symbol Table Contents

The symbol table produced by A09 is a bit more verbose than the original. For each symbol, it lists the symbol name, type, and value. The following symbol types can occur:

Relocation Table Contents

The Relocation Table is something which doesn't exist in the original. When in Relocating mode, A09 creates this table to show where a relocation is to be applied. For each entry, A09 lists the symbol name, type, and the relocation address. There can be a '-' prepended to the symbol name to indicate that the symbol is to be subtracted from the value at the relocation address (normally, the symbol is added). The relocation table uses the same set of types as the symbol table.

Things that are.. and things that aren't

My version of A09 aims to reproduce the behaviour of the Flex9 ASMB and RELASMB products. As of now, it reproduces about 99% of the originals' functionality, and surpasses them in some areas. Some things still aren't implemented, however.

Symbols

A09 normally handles symbols with up to 32 significant characters. This is far more than the 6 (ASMB) or 8 (RELASMB) places in the predecessors and normally quite convenient, but it can cause problems when

• dealing with old sources that rely on the old maximum to work
• creating RELASMB-compatible relocatable modules

Local Labels

This nice feature of RELASMB has been added to A09, too. Due to the completely different implementation, and since A09 doesn't have to work in the extremely limited address space available to a 6809, A09 isn't restricted to 100 local labels; you can define as many local labels as you want to. The only restriction is that the length of the all-numeric symbol must be less than the number of significant symbol characters (see above) so that the B and F character can be appended in references to the local label.

External Expressions

When in Relocating Assembler mode, you can define external labels (i.e., labels that refer to a location in another module, that are resolved by the Linker/Loader at a later time). These labels can be used in expressions, but in a more restricted way than in RELASMB, due to the way the parser works. If there is  a mixture of relocatable and external elements in the expression, the relocatable elements have to be in pairs so that they effectively cancel each other's effect, just like in the original - but, additionally, the external label has to be either the last element in the expression or the paired relocatable elements have to be parenthesized. As an example,

rel1-rel2+ext1-rel2+rel1

rel1-rel2-rel2+rel1+ext1
(rel1-rel2)+ext1-(rel2-rel1)

The command line switch that instructs RELASMB to treat all undefined labels as external labels isn't implemented.

Fix Mode

RELASMB's Fix Mode is not implemented. While that may be a nifty feature, it can easily be replaced by a combination of TEXT and IF directives, which offer a better control over what gets assembled and what not.