# HG changeset patch
# User lost
# Date 1267336507 0
# Node ID ed35532965800eb3b008d1671bd074100db04567
# Parent 81c005b82775573143b63556be4783fa22f43e82
Port manual forward with corrections from Jason Law
diff -r 81c005b82775 -r ed3553296580 doc/Makefile.am
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/Makefile.am Sun Feb 28 05:55:07 2010 +0000
@@ -0,0 +1,3 @@
+EXTRA_DIST = lwasm.txt internals.txt manual.docbook.sgml manual
+
+
diff -r 81c005b82775 -r ed3553296580 doc/README
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/README Sun Feb 28 05:55:07 2010 +0000
@@ -0,0 +1,13 @@
+If there are no html files in the "manual" directory and there is no
+"manual.html" file, it means that you have either checked out the source
+repository on a non-release branch or the packager messed up.
+
+In either case, if you have "docbook2html" installed, you should be able
+to build the manual with one of the following:
+
+docbook2html -o manual manual.docbook.sgml
+
+or
+
+docbook2html -u manual.docbook.sgml && mv manual.docbook.html manual/manual.html
+
diff -r 81c005b82775 -r ed3553296580 doc/internals.txt
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/internals.txt Sun Feb 28 05:55:07 2010 +0000
@@ -0,0 +1,49 @@
+LWASM Internals
+===============
+
+LWASM is a table-driven assembler that notionally uses two passes. However,
+it implements its assembly in several passes as follows.
+
+Pass 1 - Preprocessing & Parsing
+--------------------------------
+
+This pass reads the source file and all included source files. It handles
+macro definition and expansion.
+
+As it reads the various lines, it also identifies any symbol associated with
+the line, the operation code, and, based on the operation code, the operand,
+if any. Upon examination of the operand, any expressions are stored in an
+internal postfix notation for later evaluation. During this pass,
+preliminary values are assigned to all symbols using the largest possible
+instruction size. A table of lines that reference every symbol is generated
+to be used in the following pass. Note that any symbols for which the value
+is known with no uncertainty factor will be generated with the smallest
+possible instruction.
+
+At this stage, simple optimizations are performed on expressions. This
+includes coalescing constants (1+2+x => 3+x). It also includes some basic
+algebra (x+x => 2*x, 2*x+4*x => 6*x, x-x => 0).
+
+Pass 2 - Optimization
+---------------------
+
+This pass sweeps the code looking for operations which could use a shorter
+instruction. If it finds one, it must then re-define all symbols defined
+subsequently and all symbols defined in terms of one of those symbols in a
+cascade. This process is repeated until no more possible reductions are
+discovered.
+
+If, in the process of implementing an instruction reduction, a phasing error
+or other conflict is encountered, the reduction is backed out and marked as
+forced.
+
+The following may be candidates for reduction, depending on assembler
+options:
+
+- extended addressing -> direct addressing (not in obj target)
+- 16 bit offset -> 8 bit offset (indirect indexed)
+- 16 bit offset -> 8 bit or 5 bit offset (direct indexed)
+- 16 bit offset -> no offset (indexed)
+- 16 bit relative -> 8 bit relative (depending on configuration)
+
+
diff -r 81c005b82775 -r ed3553296580 doc/lwasm.txt
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/lwasm.txt Sun Feb 28 05:55:07 2010 +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.
+
diff -r 81c005b82775 -r ed3553296580 doc/manual.docbook.sgml
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/manual.docbook.sgml Sun Feb 28 05:55:07 2010 +0000
@@ -0,0 +1,2112 @@
+
+
+
+LW Tool Chain
+WilliamAstle
+2009William Astle
+
+
+
+Introduction
+
+
+The LW tool chain provides utilities for building binaries for MC6809 and
+HD6309 CPUs. The tool chain includes a cross-assembler and a cross-linker
+which support several styles of output.
+
+
+
+History
+
+For a long time, I have had an interest in creating an operating system for
+the Coco3. I finally started working on that project around the beginning of
+2006. I had a number of assemblers I could choose from. Eventually, I settled
+on one and started tinkering. After a while, I realized that assembler was not
+going to be sufficient due to lack of macros and issues with forward references.
+Then I tried another which handled forward references correctly but still did
+not support macros. I looked around at other assemblers and they all lacked
+one feature or another that I really wanted for creating my operating system.
+
+
+
+The solution seemed clear at that point. I am a fair programmer so I figured
+I could write an assembler that would do everything I wanted an assembler to
+do. Thus the LWASM probject was born. After more than two years of on and off
+work, version 1.0 of LWASM was released in October of 2008.
+
+
+
+As the aforementioned operating system project progressed further, it became
+clear that while assembling the whole project through a single file was doable,
+it was not practical. When I found myself playing some fancy games with macros
+in a bid to simulate sections, I realized I needed a means of assembling
+source files separately and linking them later. This spawned a major development
+effort to add an object file support to LWASM. It also spawned the LWLINK
+project to provide a means to actually link the files.
+
+
+
+
+
+
+
+Output Formats
+
+
+The LW tool chain supports multiple output formats. Each format has its
+advantages and disadvantages. Each format is described below.
+
+
+
+Raw Binaries
+
+A raw binary is simply a string of bytes. There are no headers or other
+niceties. Both LWLINK and LWASM support generating raw binaries. ORG directives
+in the source code only serve to set the addresses that will be used for
+symbols but otherwise have no direct impact on the resulting binary.
+
+
+
+
+DECB Binaries
+
+A DECB binary is compatible with the LOADM command in Disk Extended
+Color Basic on the CoCo. They are also compatible with CLOADM from Extended
+Color Basic. These binaries include the load address of the binary as well
+as encoding an execution address. These binaries may contain multiple loadable
+sections, each of which has its own load address.
+
+
+Each binary starts with a preamble. Each preamble is five bytes long. The
+first byte is zero. The next two bytes specify the number of bytes to load
+and the last two bytes specify the address to load the bytes at. Then, a
+string of bytes follows. After this string of bytes, there may be another
+preamble or a postamble. A postamble is also five bytes in length. The first
+byte of the postamble is $FF, the next two are zero, and the last two are
+the execution address for the binary.
+
+
+
+Both LWASM and LWLINK can output this format.
+
+
+
+
+OS9 Modules
+
+
+Since version 2.5, LWASM is able to generate OS9 modules. The syntax is
+basically the same as for other assemblers. A module starts with the MOD
+directive and ends with the EMOD directive. The OS9 directive is provided
+as a shortcut for writing system calls.
+
+
+
+
+
+LWASM does NOT provide an OS9Defs file. You must provide your own. Also note
+that the common practice of using "ifp1" around the inclusion of the OS9Defs
+file is discouraged as it is pointless and can lead to unintentional
+problems and phasing errors. Because LWASM reads each file exactly once,
+there is no benefit to restricting the inclusion to the first assembly pass.
+
+
+
+
+
+It is also critical to understand that unlike many OS9 assemblers, LWASM
+does NOT maintain a separate data address counter. Thus, you must define
+all your data offsets and so on outside of the mod/emod segment. It is,
+therefore, likely that source code targeted at other assemblers will require
+edits to build correctly.
+
+
+
+
+
+LWLINK does not, yet, have the ability to create OS9 modules from object
+files.
+
+
+
+
+
+Object Files
+LWASM supports generating a proprietary object file format which is
+described in . LWLINK is then used to link these
+object files into a final binary in any of LWLINK's supported binary
+formats.
+
+Object files also support the concept of sections which are not valid
+for other output types. This allows related code from each object file
+linked to be collapsed together in the final binary.
+
+
+Object files are very flexible in that they allow references that are not
+known at assembly time to be resolved at link time. However, because the
+addresses of such references are not known at assembly time, there is no way
+for the assembler to deduce that an eight bit addressing mode is possible.
+That means the assember will default to using sixteen bit addressing
+whenever an external or cross-section reference is used.
+
+
+
+As of LWASM 2.4, it is possible to force direct page addressing for an
+external reference. Care must be taken to ensure the resulting addresses
+are really in the direct page since the linker does not know what the direct
+page is supposed to be and does not emit errors for byte overflows.
+
+
+
+It is also possible to use external references in an eight bit immediate
+mode instruction. In this case, only the low order eight bits will be used.
+Again, no byte overflows will be flagged.
+
+
+
+
+
+
+
+
+LWASM
+
+The LWTOOLS assembler is called LWASM. This chapter documents the various
+features of the assembler. It is not, however, a tutorial on 6x09 assembly
+language programming.
+
+
+
+Command Line Options
+
+The binary for LWASM is called "lwasm". Note that the binary is in lower
+case. lwasm takes the following command line arguments.
+
+
+
+
+
+
+
+
+
+This will cause the assembler to accept the additional instructions available
+on the 6309 processor. This is the default mode; this option is provided for
+completeness and to override preset command arguments.
+
+
+
+
+
+
+
+
+
+This will cause the assembler to reject instructions that are only available
+on the 6309 processor.
+
+
+
+
+
+
+
+
+
+Select the DECB output format target. Equivalent to .
+
+While this is the default output format currently, it is not safe to rely
+on that fact. Future versions may have different defaults. It is also trivial
+to modify the source code to change the default. Thus, it is recommended to specify
+this option if you need DECB output.
+
+
+
+
+
+
+
+
+Select the output format. Valid values are for the
+object file target, for the DECB LOADM format,
+ for creating OS9 modules, and for
+a raw binary.
+
+
+
+
+
+
+
+
+
+Cause LWASM to generate a listing. If is specified,
+the listing will go to that file. Otherwise it will go to the standard output
+stream. By default, no listing is generated.
+
+
+
+
+
+
+
+
+Select the proprietary object file format as the output target.
+
+
+
+
+
+
+
+
+
+This option specifies the name of the output file. If not specified, the
+default is .
+
+
+
+
+
+
+
+
+
+Specify assembler pragmas. Multiple pragmas are separated by commas. The
+pragmas accepted are the same as for the PRAGMA assembler directive described
+below.
+
+
+
+
+
+
+
+
+
+Select raw binary as the output target.
+
+
+
+
+
+
+
+
+
+Add to the end of the include path.
+
+
+
+
+
+
+
+
+
+Present a help screen describing the command line options.
+
+
+
+
+
+
+
+
+Provide a summary of the command line options.
+
+
+
+
+
+
+
+
+
+Display the software version.
+
+
+
+
+
+
+
+
+
+Increase the debugging level. Only really useful to people hacking on the
+LWASM source code itself.
+
+
+
+
+
+
+
+
+
+Dialects
+
+LWASM supports all documented MC6809 instructions as defined by Motorola.
+It also supports all known HD6309 instructions. While there is general
+agreement on the pneumonics for most of the 6309 instructions, there is some
+variance with the block transfer instructions. TFM for all four variations
+seems to have gained the most traction and, thus, this is the form that is
+recommended for LWASM. However, it also supports COPY, COPY-, IMP, EXP,
+TFRP, TFRM, TFRS, and TFRR. It further adds COPY+ as a synomym for COPY,
+IMPLODE for IMP, and EXPAND for EXP.
+
+
+By default, LWASM accepts 6309 instructions. However, using the
+--6809 parameter, you can cause it to throw errors on
+6309 instructions instead.
+
+
+The standard addressing mode specifiers are supported. These are the
+hash sign ("#") for immediate mode, the less than sign ("<") for forced
+eight bit modes, and the greater than sign (">") for forced sixteen bit modes.
+
+
+
+Additionally, LWASM supports using the asterisk ("*") to indicate
+base page addressing. This should not be used in hand-written source code,
+however, because it is non-standard and may or may not be present in future
+versions of LWASM.
+
+
+
+
+
+Source Format
+
+
+LWASM accepts plain text files in a relatively free form. It can handle
+lines terminated with CR, LF, CRLF, or LFCR which means it should be able
+to assemble files on any platform on which it compiles.
+
+
+Each line may start with a symbol. If a symbol is present, there must not
+be any whitespace preceding it. It is legal for a line to contain nothing
+but a symbol.
+
+The op code is separated from the symbol by whitespace. If there is
+no symbol, there must be at least one white space character preceding it.
+If applicable, the operand follows separated by whitespace. Following the
+opcode and operand is an optional comment.
+
+
+A comment can also be introduced with a * or a ;. The comment character is
+optional for end of statement comments. However, if a symbol is the only
+thing present on the line other than the comment, the comment character is
+mandatory to prevent the assembler from interpreting the comment as an opcode.
+
+
+
+For compatibility with the output generated by some C preprocessors, LWASM
+will also ignore lines that begin with a #. This should not be used as a general
+comment character, however.
+
+
+
+The opcode is not treated case sensitively. Neither are register names in
+the operand fields. Symbols, however, are case sensitive.
+
+
+ As of version 2.6, LWASM supports files with line numbers. If line
+numbers are present, the line must start with a digit. The line number
+itself must consist only of digits. The line number must then be followed
+by either the end of the line or exactly one white space character. After
+that white space character, the lines are interpreted exactly as above.
+
+
+
+
+
+Symbols
+
+
+Symbols have no length restriction. They may contain letters, numbers, dots,
+dollar signs, and underscores. They must start with a letter, dot, or
+underscore.
+
+
+
+LWASM also supports the concept of a local symbol. A local symbol is one
+which contains either a "?" or a "@", which can appear anywhere in the symbol.
+The scope of a local symbol is determined by a number of factors. First,
+each included file gets its own local symbol scope. A blank line will also
+be considered a local scope barrier. Macros each have their own local symbol
+scope as well (which has a side effect that you cannot use a local symbol
+as an argument to a macro). There are other factors as well. In general,
+a local symbol is restricted to the block of code it is defined within.
+
+
+
+By default, unless assembling to the os9 target, a "$" in the symbol will
+also make it local. This can be controlled by the "dollarlocal" and
+"nodollarlocal" pragmas. In the absence of a pragma to the contrary, For
+the os9 target, a "$" in the symbol will not make it considered local while
+for all other targets it will.
+
+
+
+
+
+Numbers and Expressions
+
+
+Numbers can be expressed in binary, octal, decimal, or hexadecimal. Binary
+numbers may be prefixed with a "%" symbol or suffixed with a "b" or "B".
+Octal numbers may be prefixed with "@" or suffixed with "Q", "q", "O", or
+"o". Hexadecimal numbers may be prefixed with "$", "0x" or "0X", or suffixed
+with "H". No prefix or suffix is required for decimal numbers but they can
+be prefixed with "&" if desired. Any constant which begins with a letter
+must be expressed with the correct prefix base identifier or be prefixed
+with a 0. Thus hexadecimal FF would have to be written either 0FFH or $FF.
+Numbers are not case sensitive.
+
+
+
+ A symbol may appear at any point where a number is acceptable. The
+special symbol "*" can be used to represent the starting address of the
+current source line within expressions.
+
+The ASCII value of a character can be included by prefixing it with a
+single quote ('). The ASCII values of two characters can be included by
+prefixing the characters with a quote (").
+
+
+
+LWASM supports the following basic binary operators: +, -, *, /, and %.
+These represent addition, subtraction, multiplication, division, and
+modulus. It also supports unary negation and unary 1's complement (- and ^
+respectively). It is also possible to use ~ for the unary 1's complement
+operator. For completeness, a unary positive (+) is supported though it is
+a no-op. LWASM also supports using |, &, and ^ for bitwise or, bitwise and,
+and bitwise exclusive or respectively.
+
+
+
+
+
+Operator precedence follows the usual rules. Multiplication, division, and
+modulus take precedence over addition and subtraction. Unary operators take
+precedence over binary operators. Bitwise operators are lower precdence
+than addition and subtraction. To force a specific order of evaluation,
+parentheses can be used in the usual manner.
+
+
+
+
+
+As of LWASM 2.5, the operators && and || are recognized for boolean and and
+boolean or respectively. They will return either 0 or 1 (false or true).
+They have the lowest precedence of all the binary operators.
+
+
+
+
+
+
+Assembler Directives
+
+Various directives can be used to control the behaviour of the
+assembler or to include non-code/data in the resulting output. Those directives
+that are not described in detail in other sections of this document are
+described below.
+
+
+
+Data Directives
+
+FCB expr[,...]
+.DB expr[,...]
+.BYTE expr[,...]
+
+Include one or more constant bytes (separated by commas) in the output.
+
+
+
+
+FDB expr[,...]
+.DW expr[,...]
+.WORD expr[,...]
+
+Include one or more words (separated by commas) in the output.
+
+
+
+
+FQB expr[,...]
+.QUAD expr[,...]
+.4BYTE expr[,...]
+
+Include one or more double words (separated by commas) in the output.
+
+
+
+
+FCC string
+.ASCII string
+.STR string
+
+
+Include a string of text in the output. The first character of the operand
+is the delimiter which must appear as the last character and cannot appear
+within the string. The string is included with no modifications>
+
+
+
+
+
+FCN string
+.ASCIZ string
+.STRZ string
+
+
+Include a NUL terminated string of text in the output. The first character of
+the operand is the delimiter which must appear as the last character and
+cannot appear within the string. A NUL byte is automatically appended to
+the string.
+
+
+
+
+
+FCS string
+.ASCIS string
+.STRS string
+
+
+Include a string of text in the output with bit 7 of the final byte set. The
+first character of the operand is the delimiter which must appear as the last
+character and cannot appear within the string.
+
+
+
+
+ZMB expr
+
+
+Include a number of NUL bytes in the output. The number must be fully resolvable
+during pass 1 of assembly so no forward or external references are permitted.
+
+
+
+
+ZMD expr
+
+
+Include a number of zero words in the output. The number must be fully
+resolvable during pass 1 of assembly so no forward or external references are
+permitted.
+
+
+
+
+ZMQ expr
+
+
+Include a number of zero double-words in the output. The number must be fully
+resolvable during pass 1 of assembly so no forward or external references are
+permitted.
+
+
+
+
+
+RMB expr
+.BLKB expr
+.DS expr
+.RS expr
+
+
+Reserve a number of bytes in the output. The number must be fully resolvable
+during pass 1 of assembly so no forward or external references are permitted.
+The value of the bytes is undefined.
+
+
+
+
+RMD expr
+
+
+Reserve a number of words in the output. The number must be fully
+resolvable during pass 1 of assembly so no forward or external references are
+permitted. The value of the words is undefined.
+
+
+
+
+RMQ expr
+
+
+Reserve a number of double-words in the output. The number must be fully
+resolvable during pass 1 of assembly so no forward or external references are
+permitted. The value of the double-words is undefined.
+
+
+
+
+
+INCLUDEBIN filename
+
+
+Treat the contents of filename as a string of bytes to
+be included literally at the current assembly point. This has the same effect
+as converting the file contents to a series of FCB statements and including
+those at the current assembly point.
+
+
+ If filename beings with a /, the file name
+will be taken as absolute. Otherwise, the current directory will be
+searched followed by the search path in the order specified.
+
+ Please note that absolute path detection including drive letters will
+not function correctly on Windows platforms. Non-absolute inclusion will
+work, however.
+
+
+
+
+
+
+
+
+
+Address Definition
+The directives in this section all control the addresses of symbols
+or the assembly process itself.
+
+
+ORG expr
+
+Set the assembly address. The address must be fully resolvable on the
+first pass so no external or forward references are permitted. ORG is not
+permitted within sections when outputting to object files. For the DECB
+target, each ORG directive after which output is generated will cause
+a new preamble to be output. ORG is only used to determine the addresses
+of symbols when the raw target is used.
+
+
+
+
+
+sym EQU expr
+sym = expr
+
+Define the value of sym to be expr.
+
+
+
+
+sym SET expr
+
+Define the value of sym to be expr.
+Unlike EQU, SET permits symbols to be defined multiple times as long as SET
+is used for all instances. Use of the symbol before the first SET statement
+that sets its value is undefined.
+
+
+
+
+SETDP expr
+
+Inform the assembler that it can assume the DP register contains
+expr. This directive is only advice to the assembler
+to determine whether an address is in the direct page and has no effect
+on the contents of the DP register. The value must be fully resolved during
+the first assembly pass because it affects the sizes of subsequent instructions.
+
+This directive has no effect in the object file target.
+
+
+
+
+
+ALIGN expr[,value]
+
+
+Force the current assembly address to be a multiple of
+expr. If value is not
+specified, a series of NUL bytes is output to force the alignment, if
+required. Otherwise, the low order 8 bits of value
+will be used as the fill. The alignment value must be fully resolved on the
+first pass because it affects the addresses of subsquent instructions.
+However, value may include forward references; as
+long as it resolves to a constant for the second pass, the value will be
+accepted.
+
+Unless value is specified as something like $12,
+this directive is not suitable for inclusion in the middle of actual code.
+The default padding value is $00 which is intended to be used within data
+blocks.
+
+
+
+
+
+
+
+
+
+Conditional Assembly
+
+Portions of the source code can be excluded or included based on conditions
+known at assembly time. Conditionals can be nested arbitrarily deeply. The
+directives associated with conditional assembly are described in this section.
+
+All conditionals must be fully bracketed. That is, every conditional
+statement must eventually be followed by an ENDC at the same level of nesting.
+
+Conditional expressions are only evaluated on the first assembly pass.
+It is not possible to game the assembly process by having a conditional
+change its value between assembly passes. Thus there is not and never will
+be any equivalent of IFP1 or IFP2 as provided by other assemblers.
+
+
+
+IFEQ expr
+
+If expr evaluates to zero, the conditional
+will be considered true.
+
+
+
+
+
+IFNE expr
+IF expr
+
+If expr evaluates to a non-zero value, the conditional
+will be considered true.
+
+
+
+
+
+IFGT expr
+
+If expr evaluates to a value greater than zero, the conditional
+will be considered true.
+
+
+
+
+
+IFGE expr
+
+If expr evaluates to a value greater than or equal to zero, the conditional
+will be considered true.
+
+
+
+
+
+IFLT expr
+
+If expr evaluates to a value less than zero, the conditional
+will be considered true.
+
+
+
+
+
+IFLE expr
+
+If expr evaluates to a value less than or equal to zero , the conditional
+will be considered true.
+
+
+
+
+
+IFDEF sym
+
+If sym is defined at this point in the assembly
+process, the conditional
+will be considered true.
+
+
+
+
+
+IFNDEF sym
+
+If sym is not defined at this point in the assembly
+process, the conditional
+will be considered true.
+
+
+
+
+
+ELSE
+
+
+If the preceding conditional at the same level of nesting was false, the
+statements following will be assembled. If the preceding conditional at
+the same level was true, the statements following will not be assembled.
+Note that the preceding conditional might have been another ELSE statement
+although this behaviour is not guaranteed to be supported in future versions
+of LWASM.
+
+
+
+
+ENDC
+
+
+This directive marks the end of a conditional construct. Every conditional
+construct must end with an ENDC directive.
+
+
+
+
+
+
+
+
+OS9 Target Directives
+
+This section includes directives that apply solely to the OS9
+target.
+
+
+
+
+OS9 syscall
+
+
+
+This directive generates a call to the specified system call. syscall may be an arbitrary expression.
+
+
+
+
+
+
+MOD size,name,type,flags,execoff,datasize
+
+
+
+This tells LWASM that the beginning of the actual module is here. It will
+generate a module header based on the parameters specified. It will also
+begin calcuating the module CRC.
+
+
+
+
+
+The precise meaning of the various parameters is beyond the scope of this
+document since it is not a tutorial on OS9 module programming.
+
+
+
+
+
+
+
+EMOD
+
+
+
+This marks the end of a module and causes LWASM to emit the calculated CRC
+for the module.
+
+
+
+
+
+
+
+
+Miscelaneous Directives
+
+This section includes directives that do not fit into the other
+categories.
+
+
+
+
+INCLUDE filename
+USE filename
+
+ Include the contents of filename at
+this point in the assembly as though it were a part of the file currently
+being processed. Note that if whitespace appears in the name of the file,
+you must enclose filename in quotes.
+
+
+
+Note that the USE variation is provided only for compatibility with other
+assemblers. It is recommended to use the INCLUDE variation.
+
+
+
+
+
+END [expr]
+
+
+This directive causes the assembler to stop assembling immediately as though
+it ran out of input. For the DECB target only, expr
+can be used to set the execution address of the resulting binary. For all
+other targets, specifying expr will cause an error.
+
+
+
+
+
+ERROR string
+
+
+Causes a custom error message to be printed at this line. This will cause
+assembly to fail. This directive is most useful inside conditional constructs
+to cause assembly to fail if some condition that is known bad happens.
+
+
+
+
+
+.MODULE string
+
+
+This directive is ignored for most output targets. If the output target
+supports encoding a module name into it, string
+will be used as the module name.
+
+
+As of version 2.2, no supported output targets support this directive.
+
+
+
+
+
+
+
+
+
+
+Macros
+
+LWASM is a macro assembler. A macro is simply a name that stands in for a
+series of instructions. Once a macro is defined, it is used like any other
+assembler directive. Defining a macro can be considered equivalent to adding
+additional assembler directives.
+
+Macros may accept parameters. These parameters are referenced within
+a macro by the a backslash ("\") followed by a digit 1 through 9 for the first
+through ninth parameters. They may also be referenced by enclosing the
+decimal parameter number in braces ("{num}"). These parameter references
+are replaced with the verbatim text of the parameter passed to the macro. A
+reference to a non-existent parameter will be replaced by an empty string.
+Macro parameters are expanded everywhere on each source line. That means
+the parameter to a macro could be used as a symbol or it could even appear
+in a comment or could cause an entire source line to be commented out
+when the macro is expanded.
+
+
+Parameters passed to a macro are separated by commas and the parameter list
+is terminated by any whitespace. This means that neither a comma nor whitespace
+may be included in a macro parameter.
+
+
+Macro expansion is done recursively. That is, within a macro, macros are
+expanded. This can lead to infinite loops in macro expansion. If the assembler
+hangs for a long time while assembling a file that uses macros, this may be
+the reason.
+
+Each macro expansion receives its own local symbol context which is not
+inherited by any macros called by it nor is it inherited from the context
+the macro was instantiated in. That means it is possible to use local symbols
+within macros without having them collide with symbols in other macros or
+outside the macro itself. However, this also means that using a local symbol
+as a parameter to a macro, while legal, will not do what it would seem to do
+as it will result in looking up the local symbol in the macro's symbol context
+rather than the enclosing context where it came from, likely yielding either
+an undefined symbol error or bizarre assembly results.
+
+
+Note that there is no way to define a macro as local to a symbol context. All
+macros are part of the global macro namespace. However, macros have a separate
+namespace from symbols so it is possible to have a symbol with the same name
+as a macro.
+
+
+
+Macros are defined only during the first pass. Macro expansion also
+only occurs during the first pass. On the second pass, the macro
+definition is simply ignored. Macros must be defined before they are used.
+
+
+The following directives are used when defining macros.
+
+
+
+macroname MACRO
+
+This directive is used to being the definition of a macro called
+macroname. If macroname already
+exists, it is considered an error. Attempting to define a macro within a
+macro is undefined. It may work and it may not so the behaviour should not
+be relied upon.
+
+
+
+
+
+ENDM
+
+
+This directive indicates the end of the macro currently being defined. It
+causes the assembler to resume interpreting source lines as normal.
+
+
+
+
+
+
+
+Structures
+
+
+Structures are used to group related data in a fixed structure. A structure
+consists a number of fields, defined in sequential order and which take up
+specified size. The assembler does not enforce any means of access within a
+structure; it assumes that whatever you are doing, you intended to do.
+There are two pseudo ops that are used for defining structures.
+
+
+
+
+
+structname STRUCT
+
+
+
+This directive is used to begin the definition of a structure with name
+structname. Subsequent statements all form part of
+the structure definition until the end of the structure is declared.
+
+
+
+
+
+ENDSTRUCT
+
+
+This directive ends the definition of the structure.
+
+
+
+
+
+
+
+Within a structure definition, only reservation pseudo ops are permitted.
+Anything else will cause an assembly error.
+
+
+ Once a structure is defined, you can reserve an area of memory in the
+same structure by using the structure name as the opcode. Structures can
+also contain fields that are themselves structures. See the example
+below.
+
+
+tstruct2 STRUCT
+f1 rmb 1
+f2 rmb 1
+ ENDSTRUCT
+
+tstruct STRUCT
+field1 rmb 2
+field2 rmb 3
+field3 tstruct2
+ ENDSTRUCT
+
+ ORG $2000
+var1 tstruct
+var2 tstruct2
+
+
+Fields are referenced using a dot (.) as a separator. To refer to the
+generic offset within a structure, use the structure name to the left of the
+dot. If referring to a field within an actual variable, use the variable's
+symbol name to the left of the dot.
+
+You can also refer to the actual size of a structure (or a variable
+declared as a structure) using the special symbol sizeof{structname} where
+structname will be the name of the structure or the name of the
+variable.
+
+Essentially, structures are a shortcut for defining a vast number of
+symbols. When a structure is defined, the assembler creates symbols for the
+various fields in the form structname.fieldname as well as the appropriate
+sizeof{structname} symbol. When a variable is declared as a structure, the
+assembler does the same thing using the name of the variable. You will see
+these symbols in the symbol table when the assembler is instructed to
+provide a listing. For instance, the above listing will create the
+following symbols (symbol values in parentheses): tstruct2.f1 (0),
+tstruct2.f2 (1), sizeof{tstruct2} (2), tstruct.field1 (0), tstruct.field2
+(2), tstruct.field3 (5), tstruct.field3.f1 (5), tstruct.field3.f2 (6),
+sizeof{tstruct.field3} (2), sizeof{tstruct} (7), var1 {$2000}, var1.field1
+{$2000}, var1.field2 {$2002}, var1.field3 {$2005}, var1.field3.f1 {$2005},
+var1.field3.f2 {$2006}, sizeof(var1.field3} (2), sizeof{var1} (7), var2
+($2007), var2.f1 ($2007), var2.f2 ($2008), sizeof{var2} (2).
+
+
+
+
+Object Files and Sections
+
+The object file target is very useful for large project because it allows
+multiple files to be assembled independently and then linked into the final
+binary at a later time. It allows only the small portion of the project
+that was modified to be re-assembled rather than requiring the entire set
+of source code to be available to the assembler in a single assembly process.
+This can be particularly important if there are a large number of macros,
+symbol definitions, or other metadata that uses resources at assembly time.
+By far the largest benefit, however, is keeping the source files small enough
+for a mere mortal to find things in them.
+
+
+
+With multi-file projects, there needs to be a means of resolving references to
+symbols in other source files. These are known as external references. The
+addresses of these symbols cannot be known until the linker joins all the
+object files into a single binary. This means that the assembler must be
+able to output the object code without knowing the value of the symbol. This
+places some restrictions on the code generated by the assembler. For
+example, the assembler cannot generate direct page addressing for instructions
+that reference external symbols because the address of the symbol may not
+be in the direct page. Similarly, relative branches and PC relative addressing
+cannot be used in their eight bit forms. Everything that must be resolved
+by the linker must be assembled to use the largest address size possible to
+allow the linker to fill in the correct value at link time. Note that the
+same problem applies to absolute address references as well, even those in
+the same source file, because the address is not known until link time.
+
+
+
+It is often desired in multi-file projects to have code of various types grouped
+together in the final binary generated by the linker as well. The same applies
+to data. In order for the linker to do that, the bits that are to be grouped
+must be tagged in some manner. This is where the concept of sections comes in.
+Each chunk of code or data is part of a section in the object file. Then,
+when the linker reads all the object files, it coalesces all sections of the
+same name into a single section and then considers it as a unit.
+
+
+
+The existence of sections, however, raises a problem for symbols even
+within the same source file. Thus, the assembler must treat symbols from
+different sections within the same source file in the same manner as external
+symbols. That is, it must leave them for the linker to resolve at link time,
+with all the limitations that entails.
+
+
+
+In the object file target mode, LWASM requires all source lines that
+cause bytes to be output to be inside a section. Any directives that do
+not cause any bytes to be output can appear outside of a section. This includes
+such things as EQU or RMB. Even ORG can appear outside a section. ORG, however,
+makes no sense within a section because it is the linker that determines
+the starting address of the section's code, not the assembler.
+
+
+
+All symbols defined globally in the assembly process are local to the
+source file and cannot be exported. All symbols defined within a section are
+considered local to the source file unless otherwise explicitly exported.
+Symbols referenced from external source files must be declared external,
+either explicitly or by asking the assembler to assume that all undefined
+symbols are external.
+
+
+
+It is often handy to define a number of memory addresses that will be
+used for data at run-time but which need not be included in the binary file.
+These memory addresses are not initialized until run-time, either by the
+program itself or by the program loader, depending on the operating environment.
+Such sections are often known as BSS sections. LWASM supports generating
+sections with a BSS attribute set which causes the section definition including
+symbols exported from that section and those symbols required to resolve
+references from the local file, but with no actual code in the object file.
+It is illegal for any source lines within a BSS flagged section to cause any
+bytes to be output.
+
+
+The following directives apply to section handling.
+
+
+
+SECTION name[,flags]
+SECT name[,flags]
+.AREA name[,flags]
+
+
+Instructs the assembler that the code following this directive is to be
+considered part of the section name. A section name
+may appear multiple times in which case it is as though all the code from
+all the instances of that section appeared adjacent within the source file.
+However, flags may only be specified on the first
+instance of the section.
+
+There is a single flag supported in flags. The
+flag bss will cause the section to be treated as a BSS
+section and, thus, no code will be included in the object file nor will any
+bytes be permitted to be output.
+
+If the section name is "bss" or ".bss" in any combination of upper and
+lower case, the section is assumed to be a BSS section. In that case,
+the flag !bss can be used to override this assumption.
+
+
+If assembly is already happening within a section, the section is implicitly
+ended and the new section started. This is not considered an error although
+it is recommended that all sections be explicitly closed.
+
+
+
+
+
+ENDSECTION
+ENDSECT
+ENDS
+
+
+This directive ends the current section. This puts assembly outside of any
+sections until the next SECTION directive.
+
+
+
+
+sym EXTERN
+sym EXTERNAL
+sym IMPORT
+
+
+This directive defines sym as an external symbol.
+This directive may occur at any point in the source code. EXTERN definitions
+are resolved on the first pass so an EXTERN definition anywhere in the
+source file is valid for the entire file. The use of this directive is
+optional when the assembler is instructed to assume that all undefined
+symbols are external. In fact, in that mode, if the symbol is referenced
+before the EXTERN directive, an error will occur.
+
+
+
+
+
+sym EXPORT
+sym .GLOBL
+
+EXPORT sym
+.GLOBL sym
+
+
+
+This directive defines sym as an exported symbol.
+This directive may occur at any point in the source code, even before the
+definition of the exported symbol.
+
+
+Note that sym may appear as the operand or as the
+statement's symbol. If there is a symbol on the statement, that will
+take precedence over any operand that is present.
+
+
+
+
+
+
+symEXTDEP
+
+
+This directive forces an external dependency on
+sym, even if it is never referenced anywhere else in
+this file.
+
+
+
+
+
+
+
+
+Assembler Modes and Pragmas
+
+There are a number of options that affect the way assembly is performed.
+Some of these options can only be specified on the command line because
+they determine something absolute about the assembly process. These include
+such things as the output target. Other things may be switchable during
+the assembly process. These are known as pragmas and are, by definition,
+not portable between assemblers.
+
+
+LWASM supports a number of pragmas that affect code generation or
+otherwise affect the behaviour of the assembler. These may be specified by
+way of a command line option or by assembler directives. The directives
+are as follows.
+
+
+
+
+PRAGMA pragma[,...]
+
+
+Specifies that the assembler should bring into force all pragmas
+specified. Any unrecognized pragma will cause an assembly error. The new
+pragmas will take effect immediately. This directive should be used when
+the program will assemble incorrectly if the pragma is ignored or not supported.
+
+
+
+
+
+*PRAGMA pragma[,...]
+
+
+This is identical to the PRAGMA directive except no error will occur with
+unrecognized or unsupported pragmas. This directive, by virtue of starting
+with a comment character, will also be ignored by assemblers that do not
+support this directive. Use this variation if the pragma is not required
+for correct functioning of the code.
+
+
+
+
+
+Each pragma supported has a positive version and a negative version.
+The positive version enables the pragma while the negative version disables
+it. The negatitve version is simply the positive version with "no" prefixed
+to it. For instance, "pragma" vs. "nopragma". Only the positive version is
+listed below.
+
+Pragmas are not case sensitive.
+
+
+
+index0tonone
+
+
+When in force, this pragma enables an optimization affecting indexed addressing
+modes. When the offset expression in an indexed mode evaluates to zero but is
+not explicity written as 0, this will replace the operand with the equivalent
+no offset mode, thus creating slightly faster code. Because of the advantages
+of this optimization, it is enabled by default.
+
+
+
+
+
+cescapes
+
+
+This pragma will cause strings in the FCC, FCS, and FCN pseudo operations to
+have C-style escape sequences interpreted. The one departure from the official
+spec is that unrecognized escape sequences will return either the character
+immediately following the backslash or some undefined value. Do not rely
+on the behaviour of undefined escape sequences.
+
+
+
+
+
+importundefexport
+
+
+This pragma is only valid for targets that support external references. When
+in force, it will cause the EXPORT directive to act as IMPORT if the symbol
+to be exported is not defined. This is provided for compatibility with the
+output of gcc6809 and should not be used in hand written code. Because of
+the confusion this pragma can cause, it is disabled by default.
+
+
+
+
+
+undefextern
+
+
+This pragma is only valid for targets that support external references. When in
+force, if the assembler sees an undefined symbol on the second pass, it will
+automatically define it as an external symbol. This automatic definition will
+apply for the remainder of the assembly process, even if the pragma is
+subsequently turned off. Because this behaviour would be potentially surprising,
+this pragma defaults to off.
+
+
+The primary use for this pragma is for projects that share a large number of
+symbols between source files. In such cases, it is impractical to enumerate
+all the external references in every source file. This allows the assembler
+and linker to do the heavy lifting while not preventing a particular source
+module from defining a local symbol of the same name as an external symbol
+if it does not need the external symbol. (This pragma will not cause an
+automatic external definition if there is already a locally defined symbol.)
+
+
+This pragma will often be specified on the command line for large projects.
+However, depending on the specific dynamics of the project, it may be sufficient
+for one or two files to use this pragma internally.
+
+
+
+
+
+dollarlocal
+
+
+When set, a "$" in a symbol makes it local. When not set, "$" does not
+cause a symbol to be local. It is set by default except when using the OS9
+target.
+
+
+
+
+
+dollarnotlocal
+
+
+ This is the same as the "dollarlocal" pragma except its sense is
+reversed. That is, "dollarlocal" and "nodollarnotlocal" are equivalent and
+"nodollarlocal" and "dollarnotlocal" are equivalent.
+
+
+
+
+
+
+
+
+
+
+
+LWLINK
+
+The LWTOOLS linker is called LWLINK. This chapter documents the various features
+of the linker.
+
+
+
+Command Line Options
+
+The binary for LWLINK is called "lwlink". Note that the binary is in lower
+case. lwlink takes the following command line arguments.
+
+
+
+
+
+
+
+Selects the DECB output format target. This is equivalent to
+
+
+
+
+
+
+
+
+
+This option specifies the name of the output file. If not specified, the
+default is .
+
+
+
+
+
+
+
+
+
+This option specifies the output format. Valid values are
+and
+
+
+
+
+
+
+
+
+
+This option specifies the raw output format.
+It is equivalent to
+and
+
+
+
+
+
+
+
+
+
+This option allows specifying a linking script to override the linker's
+built in defaults.
+
+
+
+
+
+
+
+
+Cause section SECT to load at base address BASE. This will be prepended
+to the built-in link script. It is ignored if a link script is provided.
+
+
+
+
+
+
+
+
+
+This will output a description of the link result to FILE.
+
+
+
+
+
+
+
+
+
+Load a library using the library search path. LIBSPEC will have "lib" prepended
+and ".a" appended.
+
+
+
+
+
+
+
+
+
+Add DIR to the library search path.
+
+
+
+
+
+
+
+
+
+This option increases the debugging level. It is only useful for LWTOOLS
+developers.
+
+
+
+
+
+
+
+
+
+This provides a listing of command line options and a brief description
+of each.
+
+
+
+
+
+
+
+
+This will display a usage summary
+of each command line option.
+
+
+
+
+
+
+
+
+
+
+This will display the version of LWLINK.
+
+
+
+
+
+
+
+Linker Operation
+
+
+
+LWLINK takes one or more files in supported input formats and links them
+into a single binary. Currently supported formats are the LWTOOLS object
+file format and the archive format used by LWAR. While the precise method is
+slightly different, linking can be conceptualized as the following steps.
+
+
+
+
+
+
+First, the linker loads a linking script. If no script is specified, it
+loads a built-in default script based on the output format selected. This
+script tells the linker how to lay out the various sections in the final
+binary.
+
+
+
+
+
+Next, the linker reads all the input files into memory. At this time, it
+flags any format errors in those files. It constructs a table of symbols
+for each object at this time.
+
+
+
+
+
+The linker then proceeds with organizing the sections loaded from each file
+according to the linking script. As it does so, it is able to assign addresses
+to each symbol defined in each object file. At this time, the linker may
+also collapse different instances of the same section name into a single
+section by appending the data from each subsequent instance of the section
+to the first instance of the section.
+
+
+
+
+
+Next, the linker looks through every object file for every incomplete reference.
+It then attempts to fully resolve that reference. If it cannot do so, it
+throws an error. Once a reference is resolved, the value is placed into
+the binary code at the specified section. It should be noted that an
+incomplete reference can reference either a symbol internal to the object
+file or an external symbol which is in the export list of another object
+file.
+
+
+
+
+
+If all of the above steps are successful, the linker opens the output file
+and actually constructs the binary.
+
+
+
+
+
+
+Linking Scripts
+
+A linker script is used to instruct the linker about how to assemble the
+various sections into a completed binary. It consists of a series of
+directives which are considered in the order they are encountered.
+
+
+The sections will appear in the resulting binary in the order they are
+specified in the script file. If a referenced section is not found, the linker will behave as though the
+section did exist but had a zero size, no relocations, and no exports.
+A section should only be referenced once. Any subsequent references will have
+an undefined effect.
+
+
+
+All numbers are in linking scripts are specified in hexadecimal. All directives
+are case sensitive although the hexadecimal numbers are not.
+
+
+A section name can be specified as a "*", then any section not
+already matched by the script will be matched. The "*" can be followed
+by a comma and a flag to narrow the section down slightly, also.
+If the flag is "!bss", then any section that is not flagged as a bss section
+will be matched. If the flag is "bss", then any section that is flagged as
+bss will be matched.
+
+
+The following directives are understood in a linker script.
+
+
+section name load addr
+
+
+This causes the section name to load at
+addr. For the raw target, only one "load at" entry is
+allowed for non-bss sections and it must be the first one. For raw targets,
+it affects the addresses the linker assigns to symbols but has no other
+affect on the output. bss sections may all have separate load addresses but
+since they will not appear in the binary anyway, this is okay.
+
+For the decb target, each "load" entry will cause a new "block" to be
+output to the binary which will contain the load address. It is legal for
+sections to overlap in this manner - the linker assumes the loader will sort
+everything out.
+
+
+
+
+section name
+
+
+This will cause the section name to load after the previously listed
+section.
+
+
+exec addr or sym
+
+
+This will cause the execution address (entry point) to be the address
+specified (in hex) or the specified symbol name. The symbol name must
+match a symbol that is exported by one of the object files being linked.
+This has no effect for targets that do not encode the entry point into the
+resulting file. If not specified, the entry point is assumed to be address 0
+which is probably not what you want. The default link scripts for targets
+that support this directive automatically starts at the beginning of the
+first section (usually "init" or "code") that is emitted in the binary.
+
+
+
+
+
+pad size
+
+This will cause the output file to be padded with NUL bytes to be exactly
+size bytes in length. This only makes sense for a raw target.
+
+
+
+
+
+
+
+
+
+
+
+
+Libraries and LWAR
+
+
+LWTOOLS also includes a tool for managing libraries. These are analogous to
+the static libraries created with the "ar" tool on POSIX systems. Each library
+file contains one or more object files. The linker will treat the object
+files within a library as though they had been specified individually on
+the command line except when resolving external references. External references
+are looked up first within the object files within the library and then, if
+not found, the usual lookup based on the order the files are specified on
+the command line occurs.
+
+
+
+The tool for creating these libary files is called LWAR.
+
+
+
+Command Line Options
+
+The binary for LWAR is called "lwar". Note that the binary is in lower
+case. The options lwar understands are listed below. For archive manipulation
+options, the first non-option argument is the name of the archive. All other
+non-option arguments are the names of files to operate on.
+
+
+
+
+
+
+
+
+This option specifies that an archive is going to have files added to it.
+If the archive does not already exist, it is created. New files are added
+to the end of the archive.
+
+
+
+
+
+
+
+
+
+This option specifies that an archive is going to be created and have files
+added to it. If the archive already exists, it is truncated.
+
+
+
+
+
+
+
+
+
+If specified, any files specified to be added to an archive will be checked
+to see if they are archives themselves. If so, their constituent members are
+added to the archive. This is useful for avoiding archives containing archives.
+
+
+
+
+
+
+
+
+
+This will display a list of the files contained in the archive.
+
+
+
+
+
+
+
+
+
+This option increases the debugging level. It is only useful for LWTOOLS
+developers.
+
+
+
+
+
+
+
+
+
+This provides a listing of command line options and a brief description
+of each.
+
+
+
+
+
+
+
+
+This will display a usage summary
+of each command line option.
+
+
+
+
+
+
+
+
+
+
+This will display the version of LWLINK.
+of each.
+
+
+
+
+
+
+
+
+
+Object Files
+
+LWTOOLS uses a proprietary object file format. It is proprietary in the sense
+that it is specific to LWTOOLS, not that it is a hidden format. It would be
+hard to keep it hidden in an open source tool chain anyway. This chapter
+documents the object file format.
+
+
+
+An object file consists of a series of sections each of which contains a
+list of exported symbols, a list of incomplete references, and a list of
+"local" symbols which may be used in calculating incomplete references. Each
+section will obviously also contain the object code.
+
+
+
+Exported symbols must be completely resolved to an address within the
+section it is exported from. That is, an exported symbol must be a constant
+rather than defined in terms of other symbols.
+
+
+Each object file starts with a magic number and version number. The magic
+number is the string "LWOBJ16" for this 16 bit object file format. The only
+defined version number is currently 0. Thus, the first 8 bytes of the object
+file are 4C574F424A313600
+
+
+
+Each section has the following items in order:
+
+
+
+section name
+flags
+list of local symbols (and addresses within the section)
+list of exported symbols (and addresses within the section)
+list of incomplete references along with the expressions to calculate them
+the actual object code (for non-BSS sections)
+
+
+
+The section starts with the name of the section with a NUL termination
+followed by a series of flag bytes terminated by NUL. There are only two
+flag bytes defined. A NUL (0) indicates no more flags and a value of 1
+indicates the section is a BSS section. For a BSS section, no actual
+code is included in the object file.
+
+
+
+Either a NULL section name or end of file indicate the presence of no more
+sections.
+
+
+
+Each entry in the exported and local symbols table consists of the symbol
+(NUL terminated) followed by two bytes which contain the value in big endian
+order. The end of a symbol table is indicated by a NULL symbol name.
+
+
+
+Each entry in the incomplete references table consists of an expression
+followed by a 16 bit offset where the reference goes. Expressions are
+defined as a series of terms up to an "end of expression" term. Each term
+consists of a single byte which identifies the type of term (see below)
+followed by any data required by the term. Then end of the list is flagged
+by a NULL expression (only an end of expression term).
+
+
+
Object File Term Types
+
+
+
+TERMTYPE
+Meaning
+
+
+
+
+00
+end of expression
+
+
+
+01
+integer (16 bit in big endian order follows)
+
+
+02
+ external symbol reference (NUL terminated symbol name follows)
+
+
+
+03
+local symbol reference (NUL terminated symbol name follows)
+
+
+
+04
+operator (1 byte operator number)
+
+
+05
+section base address reference
+
+
+
+FF
+This term will set flags for the expression. Each one of these terms will set a single flag. All of them should be specified first in an expression. If they are not, the behaviour is undefined. The byte following is the flag. Flag 01 indicates an 8 bit relocation. Flag 02 indicates a zero-width relocation (see the EXTDEP pseudo op in LWASM).
+
+
+
+
+
+
+
+External references are resolved using other object files while local
+references are resolved using the local symbol table(s) from this file. This
+allows local symbols that are not exported to have the same names as
+exported symbols or external references.
+
+
+