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diff doc/lwasm.txt @ 96:7fbccdd1defb
Added doc subdirectory to distribution
author | lost |
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date | Sat, 17 Jan 2009 07:09:02 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/doc/lwasm.txt Sat Jan 17 07:09:02 2009 +0000 @@ -0,0 +1,43 @@ +LWASM 2.0 +========= + +LWASM is a cross-assembler for the MC6809 and HD6309 CPUs. It should +assemble most reasonable EDTASM compatible source code. This document is not +intended to teach assembly language for these CPUs but rather to document +the behaviour of LWASM. + + +TARGETS +------- + +LWASM supports several targets for assembly. These are decb, raw, and obj. + +The raw target generates a raw binary output. This is useful for building +ROMs and other items that are not intended to be loaded by any kind of +loader. In this mode, the ORG directive is merely advisory and does not +affect the output except for the addresses symbols are defined to have. + +The decb target generates output that can be loaded with the CLOADM or LOADM +commands in Color Basic. There will be approximately one segment in the +output file for every ORG statement after which any code is emitted. (That +is, two ORG statements in a row will not generate two output segments.) +This is approximately equivalent to running A/AO in EDTASM. + +The obj target generates output that is intended to be linked later with +LWLINK. This target disallows the use of ORG for defining anything other +than constants. In this target, source files consist of a number of sections +(SECTION/ENDSECTION). Nothing outside of a section is permitted to cause any +output at all. Use of an ORG statement within a section is an error. This +target also permits tagging symbols for export (EXPORT) and marking a symbol +as externally defined (IMPORT/EXTERN). The linker will resolve any external +references at link time. Additionally, any inter-section references will be +resolved by the linker. All code in each section is assembled with an +implicit origin of 0. SETDP has no effect because the assembler has no idea +what address the linker will assign to the code when it is linked. Any +direct addressing modes will default to extended to allow for the linker to +perform relocations. Intersegment references and external references will +use 16 bit relative addressing but intrasegment internal references may use +8 bit relative addressing. Forced 8 bit direct modes are probably an error +but are permitted on the theory that the programmer might know something the +assembler doesn't. +