CS2 Real-Time Course 1985:

            EUCSD Motorola M6809 Assembler  -  User Notes
          
   This assembler is a local implementation  of  the  Motorola  M6809
cross  assembler.  This  is  basically  documented  in   the   'M6800
Microprocessor Programming Manual' with the extensions for the  M6809
described in the 'M6809 Advance  Information'  data  sheet.  Wherever
possible it is upward compatible with the Motorola assembler and like
it, contains no macro facilites.

Differences

A) Restrictions

1) Only one program may be assembled in a single input stream.  As  a
result the MON and END directives are synonymous and optional.

2) Only object tapes are produced by the assembler. As a  result  the
OPT directive  options  MEMORY  and  OTAPE  and  their  variants  are
illegal.

3) Error messages are of a different and fixed form and hence the OPT
directive options SERROR and SER are synonymous with ERROR.


B) Extensions

1) The delimited form  of  the  FCC  directive  accepts  the  doubled
delimiter as a single instance of  the  delimiter  in  the  generated
text.
            e.g.                     FCC   /A//B/
            is the same as           FCC   'A/B'

2) The OPT directive has the following additional options:

Long form   Short form
BLANK       B           Ignores redundant spaces in operand field.  e.g. around ',' and '+'.
NOBLANK     NOB         No spaces allowed in operand field (selected by default).
CYCLE       C           Print execution time in  machine  cycles  for  each  executable statement.
NOCYCLE     NOC         No execution times printed (selected by default).
FULL        F           Allows fully parenthesised arithmetic  expressions  as  operands (see (3) below).
NOFULL      NOF         Only unparenthesised  expressions  evaluated  strictly  from left to right are allowed as operands (selected by default).
WRAP        W           Long input lines are wrapped around on to next line of listing.
NOWRAP      NOW         Long input lines  are  truncated  in  listing  (selected  by default).
XREF        X           Symbol cross reference is listed at end of listing.
NOXREF      NOX         No cross reference table is printed (selected by default).

3) By specifying OPT FULL, fully parenthesised arithmetic expressions
evaluated in the usual algebraic order are  acceptable  as  operands.
The valid binary operators are (in increasing order of precedence):
    ! (or), \ (exclusive or)
    & (and)
    +, -
    *, /, | (remainder)
    < (left shift), > (right shift)
    
The unary operators + (ignored), - and \  (complement)  are  accepted
and take precedence over all binary operators.

4)  A  '>'  expression  prefix  is  provided  which  forces  extended
addressing. This is the converse  of  the  '<'  prefix  which  forces
direct addressing.

5) The program counter relative address  mode  may  be  specified  by
offset,pc as well as label,pcr. The  former  does  not  automatically
generate a relative offset from an absolute  address  but  takes  the
value of the offset expression as the offset from the updated program
counter. For Example, the following program segments are equivalent:
lab nop jmp lab,pcr lab nop jmp lab-nxtins,pc nxtins equ *

6) Apart from catastrophic failures, error messages are generated  in
the final pass only and always immediately follow the line  to  which
they apply.

7) This is a multi-pass assembler in which there are  no  constraints
on the order of definition of symbols and which attempts to  optimise
the use of direct addressing and short  branches.  As  a  result  the
mnemonics for long  and  short  branches  are  considered  synonymous
except for BRN and LBRN.


Implementations

B) VAX and APM

M6809 file-spec

Command Qualifiers      Default
/[NO]LIST[=file-spec]   /NOLIST
/[NO]OBJECT[=file-spec] /OBJECT


Command Parameters

file-spec

Specifies a single M6809 assembler source program to be assembled.
If a file type is not specified the assembler uses the  default  file
type ASM.


Command Qualifiers

/LIST=[file-spec]
/NOLIST

   Controls whether a listing is produced.
   If file-spec is not specified the listing file has the  same
   name as the source file and has the file type LIS.

/OBJECT=[file-spec]
/NOOBJECT

   Controls whether an object code file is produced.

   If file-spec is not specified the object file has the same name as
the source file and has the file type OBJ. The object  code  produced
is in Motorola M6800 loader format.