QUICK REFERENCE FOR SPASM (SINGLE PASS ASSEMBLER) UNDER CP/M-80

Written by: Harris Landsberg       (C) Copyright 1986,1987,1988

     This documentation will aquaint you with the basics of the
SPASM  software  package.  It has been extracted  from the more
detail documentation  previously  written.  Please refer to the
SPL Language Manual for more detail about module interfacing in
object libraries. SPASM.COM  requires  CP/M-80  Version 2.2  or
higher. The cross-assembler SPASM80.EXE requires MS-DOS Version
2.0 or higher.  SLINK.COM  (or SLINK80.EXE) is required to link
the object files that are created with SPASM.

     SPASM is a single pass assembler which means it only makes
one pass through the source to produce the object code file. In
most other assembler require two or more passes.  The code that
is generated is fully relocatable containg the necessary symbol
imformation to produce a command file from multiple object code
files and use common libraries to extract only imported modules
that are necessary for the load module.

     An optional Librarian, SLIB, can optimize a object file to
remove symbol references that should not be global. It can also
create library files  by combining one or more modules from one
or more object code files.  This is similar to having  multiple
modules within an assembler source.

A: INSTRUCTION SET

     SPASM uses the standard INTEL 8080 mnemonics with no extra
modifications for the Z-80 opcodes. It does not contain a macro
facility.  All labels defined  or used are global.  It does not
use EXTRN or ENTRY instructions, but implies it. Most assembler
source written for the  standard CP/M  ASM.COM program will run
without requiring modifications.

     SPASM statement format is:

     Label     Operation    Operand    ;Comment

where any or all fields may be absent. A ':' (colon) may follow
a label, but is not required. Only one operation is allowed per
line.  Only addition, subtaction, multiplication, division  can
be done on operands  that are not registers.  Numeric constants
may be decimal or hexidecimal if followed by a 'H'. All symbols
are changed to uppercase and significant to 31 characters.
     
     The '$' by itself implies the current CODE counter and can
be used in word sized operands. SLINK defines ?CODE ?DATA ?HEAP
so they should not be defined, but can be referenced.

B: PSEUDO-MNEMONICS

     The following, in alphabetic order, are the pseudo-ops for
SPASM. There are two segments: CODE and DATA. CODE contains all
the relocatable and absolute text segments  while DATA contains
the uninitilized main storage section.  All opcodes are implied
to the CODE segment, if they generate code or use space, except
the VAR opcode which is for  variables and defines the usage of
the DATA segment. SLINK combines the segments.

     DB        <byte>[,<byte>...]

     Defines a byte storage area for constants. Can be a single
or multi-character string. Strings begin and end with a ' only.

<label>    DL      <value>

     Defines a value to the assembler.  The  DL  statement does
not this symbol into the object code and therefore local to the
source that is being assembled. See EQU.

     DS        <size>

     Defines space in memory that will be reserved.  SLINK will
initilize it to 00H.

     DW        <word>[,<word>...]

     Defines a word storage area for constants. Can be a string
of up to two characters.

     ELSE

     Allows alternate code generation in a conditional when the
condition fails.  May not be  used with a link conditional.  It
must be within
an IF and ENDIF statement.

     END

     Defines the end of a source assembler program. SPASM stops
here if not within a conditional.

     ENDIF

     Signifies the end of a conditional block. A termination of
a conditional is required and cannot be nested.

<label>    EQU     <value>

     Defines a value to the assembler. The EQU statement passes
this symbol into the object code and can be used by a different
module. See DL.

     IF        <symbol>

     Allows assembly of a section of code  if a symbol is not a
value of zero. The symbol may be a label or a constant and must
be defined prior if it is a label. See XIF.

     IMPORT    <name>[,<name>...]

     Defines the modules that are required to complete all code
references. It is used by SLINK to combine code and extract the
necessary modules from a library.

     INCLUDE   <name>

     The include file is opened and  assembled into the current
source file. Only one level is allowed. <name> can have a drive
and/or user designator in front and should have an extension of


     LIBRARY   <name>[,<name>...]

     Defines a name for an object code file to be  searched for
module references. <name> may have a drive and/or user in front
of it.  A library file is a standard object code  file with one
or more modules in it.

     ORG       <value>

     For compatibility  with other  assemblers.  Will start the
assembly listing  at the specified value,  but has no effect on
the  code generated.  The MODULE statement will set the counter
back to 0 when starting a module.

     MODULE    <name>

     Defines the beginning of a module and assigns it a name. A
module is unit of code with a unique  name that can be imported
while being search for.  It is a collection of code that cannot
be subdivided to complete a single task.  This task may be need
other support module which are imported.  Module end is implied
by end of file or start of another module. The beginning of the
source implies a module which defaults to  the source file name
unless a MODULE statement is first opcode in file.

<label>    VAR     <value>

     Defines a variable for the program. <value> is the size in
bytes that the variable requires.  <label> is a required field,
but can be removed with SLIB  (Librarian) if you want to make a
variable local.  The VAR statement defines the unitilized space
after the CODE segment known as the DATA segment.

     XIF       <label>

     Allows assembly of a section of code  with the conditional
being resolved at link time. It allows special modifications or
routines to be  included or excluded  according to a  condition
that will be not be fully known until link time.  This is known
as a LINK CONDITIONAL structure and SLINK supports it.

C: ERROR CODES

     Besides file errors,  the following errors will be flagged
by the assembler. A single uppercase character is placed at the
first first position of the line.

     C - invalid operation code
     F - file not found (INCLUDE statement)
     L - invalid label
     M - multi-defined symbol
     P - pseudo-operation error
     R - Invalid register
     S - syntax error / invalid operand

D: COMMAND LINE

     To run SPASM, type at the command line:

     SPASM [[d][u]:]<filename>  [/switch]

where  <filename>  is the only required parameter. The optional
drive and/or user area may proceed a valid filename. The output
file placed on the same drive (and user area).  The source must
have the extension .ASM  and the output will have the extension
of .OBJ appended to it.  An object file will only be created if
there are no errors in the source.

     The following are the optional /switch options:

     /F - create a listing with extension .LST
     /L - send the listing to the printer
     /S - send the listing to the screen

the default is not to list the  source.  If an error occurrs in
the source, the line is displayed at the console along with the
error message.
    
E: COMMENTS

     If you have any comments about theses products,  feel free
to write to address below. If you find any problems or bugs, it
would be appreciated to send along a copy  of the problem so it
can be duplicated and corrected.

     Also, don't forget to say which program such as:

     SPASM.COM     - CP/M-80 Version of SPASM (8080)
     SPASM80.EXE   - MS-DOS  Version of SPASM (8080) Cross Assembler
     SPASM86.EXE   - MS-DOS  Version of SPASM (8086/8087)
     SLINK.COM     - CP/M-80 Version of SLINK
     SLINK80.EXE   - MS-DOS  Version of SLINK (Cross Development)
     SLINK86.EXE   - MS-DOS  Version of SLINK (.EXE creator)

     Send Comments To:      Harris Landsberg
                          1350 East 5th Street
                               Suite 1-J
                        Brooklyn, New York 11230