A68K - 68000 Cross Assembler Notes
          
                                   11/09/82
          
          
          Command line to invoke the assembler:
          
                  A68K <filename>                   ; short form
                  A68K <object>,<listing>=<source>  ; full form
          
                  ----------------- Equivalence ----------------
          
                  XYZ                 XYZ.HEX,XYZ.PRN=XYZ.ASM
                  ,CON:=XYZ           NUL:,CON:=XYZ.ASM
                  XYZ,=XYZ            XYZ.HEX,NUL:=XYZ.ASM
                  XYZ.OBJ=XYZ.SRC     XYZ.OBJ,XYZ.PRN=XYZ.SRC
                  ,CON:=CON:          NUL:,CON:=CON:
          
                  Object file may be in Motorola S-record (default)
                  or Intel HEX format.
          
          
          <symbol>  SET   <expression>            ; temp val
          <symbol>  EQU   <expression>            ; perm val
          <symbol>  REG   <register expression>   ; perm val
          
                  Note that a size attribute may be tacked onto
                  SET or EQU to govern the way string constants
                  appearing in the expression are handled.  The
                  default size is long.  String  constants  are
                  left justified  according  to  size  and zero
                  filled.
          
          <register expression>          for use in MOVEM
                  <Rn>    <next reg>
          
          <next reg>
                  - <Rn>   <next reg>
                  /        <register expression>
          
          <Rn>
                  A <rnum>
                  D <rnum>
          
          
          Labels are symbols which receive the current value of
                  the program counter.
                  For labels beginning in column 1, colon is optional.
                  For labels preceded by blanks,    colon is required.
          
          
                    OPT   <option>,<option>,.....
          
          <option>
                  BRL     ; long  branch forward ref. - default
                  BRS     ; short branch forward ref.
                  FRL     ; long  absolute fwd. ref.  - default
                  FRS     ; short absolute fwd. ref.
                  OBJ-S   ; hex file Motorola style   - default
                  OBJ-H   ; hex file Intel style (16 bit address limit)
 

 
 

 
                  NOP1L   ; no pass 1 listing         - default
                  P1L     ;    pass 1 listing
          
          
          * <comment>
          
          
           .S & .L  may be appended to BRA, BSR, Bcc, JMP and JSR
                  to override automatic size determination.
                  They  may  also  be   appended  to  absolute  address
                  operands in other instructions.  But, it is necessary
                  to isolate  the  period  from a  symbol  by enclosing
                  the symbol in parentheses.  This  is  due to the fact
                  that period is a valid character in symbols.
          
          
          <symbol>
                  Symbols begin with a letter or period.  Additional
                  characters may be letters, digits, periods, dollar
                  signs and underscores.
          
                  * represents the program counter
          
                  Symbols may have up to 31 significant characters.
          
                  The symbol table is currently of fixed size:
                           500 Symbols max
                          2000 Characters max
          
          
          Constants begin with:
                  char    - '
                  hex     - $
                  octal   - @
                  binary  - %
                  decimal - 0 thru 9
          
          
          Strings:
                  Delimited by '
                  '' represents '
          
          
          Expressions and symbols are classified as constants
                  or addresses.
          
          
          Operators for expressions (in precedence group order):
          
                  + -
          
                  * /        only implemented for 16 bits now
                  \          mod - only 16 bits for now
          
                  &          AND
                  ! |        both allowed for OR
                  ^          exclusive OR
          
                  <<         shift left
                  >>         shift right
 

 
 

 
          
                  -          unary minus
                  ~          unary NOT
          
                  Except for + and -,  only  expressions  which evaluate
                  constants are allowed as  operands to  operators.  For
                  + and -, (a + a) and (c - a) produce errors.  Embedded
                  spaces are not allowed in expressions (spaces serve as
                  field delimiters).
          
          
          Automatic conversions:
          
                  ADD     #e   ,<ea>      ADDQ or ADDI when possible
                          <ea> ,An        ADDA
          
                  SUB     #e   ,<ea>      SUBQ or SUBI when possible
                          <ea> ,An        ADDA
          
                  CMP     #e   ,<ea>      CMPI when possible
                          (An)+,(An)+     CMPM
                          <ea> ,An        CMPA
          
                  AND     #e   ,<ea>      ANDI when possible
          
                  OR      #e   ,<ea>      ORI  when possible
          
                  EOR     #e   ,<ea>      EORI when possible
          
          
          Addressing Mode Syntax Interpretation:
          
                          c  expression must evaluate to constant
                          a  expression must evaluate to address
                          b  expression may  evaluate to either
          
              Syntax used            Interpreted as    Mode,reg
                  # e                     #c              7,4
          
                  D n                     Dn              0
          
                  A n                     An              1
          
                  - ( A n )               -(An)           4
          
                  ( A n ) +               (An)+           3
          
                  ( A n )                 (An)            2
          
                  ( A n , R i )
                  ( A n , R i . W )       0(An,Ri.s)      6
                  ( A n , R i . L )
          
                  e ( A n , R i )
                  e ( A n , R i . W )     c(An,Ri.s)      6
                  e ( A n , R i . L )
          
                  e ( A n )               c(An)           5
          
                  e ( D i )
 

 
 

 
                  e ( R i . W )           a(PC,Ri.s)      7,3
                  e ( R i . L )
          
                  e ( PC , R i )
                  e ( PC , R i . W )      a(PC,Ri.s)      7,3
                  e ( PC , R i . L )
          
                  e ( PC )                a(PC)           7,2
          
                  e . L                   b.L             7,1          **
          
                  e . S                   b.S             7,0          **
          
                  e                       b               7,0 or 7,1   **
          
                  ****   SP may be used for A7 anywhere An appears, but not
                  where Ri appears for index specification.
          
                  **     Explicit  range   specification   via   (.S or .L)
                  overrides  the  automatic range  selection  for  absolute
                  addressing.  For auto, if the expression contains forward
                  references, the  range is  determined by  the "FR" option
                  currently in  effect  (FRL default).   If  the expression
                  contains  no  forward references, the range is made short
                  if the expression lies between -32768 and +32767.