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                                    MOTOROLA
 
                                    FREEWARE
 
                             8-BIT CROSS ASSEMBLERS
 
                                  USER'S MANUAL
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                     EDITED BY
 
                                   KEVIN ANDERSON
 
                             FIELD APPLICATIONS ENGINEER
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                           TABLE OF CONTENTS
 
CHAPTER 1.........................................................  1
 
     1.1   INTRODUCTION ..........................................  1
     1.2   ASSEMBLY LANGUAGE .....................................  1
     1.3   OPERATING ENVIRONMENT .................................  2
     1.4   ASSEMBLER PROCESSING ..................................  2
 
CHAPTER 2 ........................................................  3
 
     2.1   INTRODUCTION ..........................................  3
     2.2   SOURCE STATEMENT FORMAT ...............................  3
          2.2.1   Label Field ....................................  3
          2.2.2   Operation Field ................................  4
          2.2.3   Operand Field ..................................  4
               2.2.3.1  M6800/6801 Operand Syntax ................  5
               2.2.3.2  M6800/M68HC04 Operand Syntax .............  5
               2.2.3.3  M6805/M68HC05 Operand Syntax .............  5
               2.2.3.4  M6809 Operand Syntax .....................  5
               2.2.3.5  M68HC11 Operand Syntax ...................  6
               2.2.3.6  Expressions ..............................  6
               2.2.3.7  Operators ................................  7
               2.2.3.8  Symbols ..................................  7
               2.2.3.9  Constants ................................  7
          2.2.4   Comment Field ..................................  8
     2.3   ASSEMBLER OUTPUT ......................................  9
 
CHAPTER 3 - RUNNING THE ASSEMBLERS ...............................  10
 
     3.1   ASSEMBLER INVOCATION ..................................  10
     3.2   ERROR MESSAGES ........................................  11
 
CHAPTER 4 - ASSEMBLER DIRECTIVES .................................  12
 
     4.1   INTRODUCTION ..........................................  12
     4.2   BSZ - BLOCK STORAGE OF ZEROS ..........................  12
     4.3   EQU - EQUATE SYMBOL TO A VALUE ........................  13
     4.4   FCB - FORM CONSTANT BYTE ..............................  13
     4.5   FCC - FORM CONSTANT CHARACTER STRING ..................  13
     4.6   FDB - FROM DOUBLE BYTE CONSTANT .......................  13
     4.7   FILL - FILL MEMORY ....................................  14
     4.8   OPT - ASSEMBLER OUTPUT OPTIONS ........................  14
     4.9   ORG - SET PROGRAM COUNTER TO ORIGIN ...................  14
     4.10   PAGE - TOP OF PAGE ...................................  15
     4.11   RMB - RESERVE MEMORY BYTES ...........................  15
     4.12   ZMB - ZERO MEMORY BYTES ..............................  15
 
APPENDIX A - CHARACTER SET .......................................  16
 
APPENDIX B - ADDRESSING MODES ....................................  18
 
     B.1   M6800/M6801 ADDRESSING MODES ..........................  18
     B.2   M6804/68HC04 ADDRESSING MODES .........................  19
     B.3   M6805/68HC05 ADDRESSING MODES .........................  21
 
 
 
                                i
 
 
 
 
 
 
 
                           TABLE OF CONTENTS
 
     B.4   M6809 ADDRESSING MODES ................................  22
     B.5   M68HC11 ADDRESSING MODES ..............................  26
 
APPENDIX C - DIRECTIVE SUMMARY ...................................  28
 
APPENDIX D - ASSEMBLER LISTING FORMAT ............................  29
 
APPENDIX E - S-RECORD INFORMATION ................................  30
 
     E.1   INTRODUCTION ..........................................  30
     E.2   S-RECORD CONTENT ......................................  30
     E.3   S-RECORD TYPES ........................................  30
     E.4   S-RECORD EXAMPLE ......................................  31
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                ii
 
 
 
 
 
 
 
                               CHAPTER 1
                          GENERAL INFORMATION
 
 
1.1   INTRODUCTION
 
This is the user's reference manual for the IBM-PC hosted Motorola
Freeware 8 bit cross assemblers.  It details the features and
capabilities of the cross assemblers, assembler syntax and directives,
options, and listings. It is intended as a detailed reference and an
introduction for those unfamiliar with Motorola assembler syntax and
format.  Those experienced with Motorola assembler products may wish
to examine the file ASEMBLER.DOC available with the cross assemblers,
which briefly describes the differences between these assemblers and
earlier, non-pc based versions.
 
Assemblers are programs that process assembly language source program
statements and translate them into executable machine language object
files.  A programmer writes his source program using any text editor
or word processor that can produce an ASCII text output.  With some
word processors this is known as "non document" mode.  Non document
mode produces a file without the non-printable embedded control
characters that are used in document formating.  (Caution: assembling
a file that has been formatted with embedded control characters may
produce assembler errors.  The solution is to convert the source file
to ASCII text.) Once the source code is written, the source file is
assembled by processing the file via the assembler.
 
Cross assemblers (such as the Motorola Freeware Assemblers) allow
source programs written and edited on one computer (the host) to
generate executable code for another computer (the target).  The
executable object file can then be downloaded and run on the target
system.  In this case the host is an IBM-PC or compatible and the
target system is based on a Motorola 8-bit microprocessor (6800, 6801,
6803, 6805, 68HC05, 6809, or 68HC11).
 
The assemblers are the executable programs AS*.EXE where * is any of
0, 1, 4, 5, 9, or 11 depending on which microprocessor you are writing
code for.  The details of executing the assembler programs are found
in Chapter 3.  The assembly language format and syntax for the various
processors is very similar with slight variations due to varied
programming resources (instructions, addressing modes, and registers).
These variations are explained in Appendix B.
 
 
1.2   ASSEMBLY LANGUAGE
 
The symbolic language used to code source programs to be processed by
the Assembler is called assembly language. The language is a
collection of mnemonic symbols representing: operations (i.e., machine
instruction mnemonics or directives to the assembler), symbolic names,
operators, and special symbols. The assembly language provides
mnemonic operation codes for all machine instructions in the
instruction set. The instructions are defined and explained in the
Programming Reference Manuals for the specific devices, available from
Motorola. The assembly language also contains mnemonic directives
 
 
 
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
which specify auxiliary actions to be performed by the Assembler.
These directives are not always translated into machine language.
 
 
1.3   OPERATING ENVIRONMENT
 
These assemblers will run on any IBM-PC, XT, AT, PS-2, or true
compatible.  The assemblers may be run off of a floppy disk drive or
they may be copied onto a hard drive for execution.  DOS 2.0 or later
is required.
 
 
1.4   ASSEMBLER PROCESSING
 
The Macro Assembler is a two-pass assembler. During the first pass,
the source program is read to develop the symbol table. During the
second pass, the object file is created (assembled) with reference to
the table developed in pass one. It is during the second pass that
the source program listing is also produced.
 
Each source statement is processed completely before the next source
statement is read. As each statement is processed, the Assembler
examines the label, operation code, and operand fields. The operation
code table is scanned for a match with a known opcode.  During the
processing of a standard operation code mnemonic, the standard
machine code is inserted into the object file. If an Assembler
directive is being processed, the proper action is taken.
 
Any errors that are detected by the Assembler are displayed before the
actual line containing the error is printed. If no source listing is
being produced, error messages are still displayed to indicate that
the assembly process did not proceed normally.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                 2
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                              CHAPTER 2
                   CODING ASSEMBLY LANGUAGE PROGRAMS
 
 
2.1   INTRODUCTION
 
Programs written in assembly language consist of a sequence of source
statements. Each source statement consists of a sequence of ASCII
characters ending with a carriage return.  Appendix A contains a list
of the supported character set.
 
 
2.2   SOURCE  STATEMENT FORMAT
 
Each source statement may include up to four fields:  a label (or "*"
for a comment line), an operation (instruction mneumonic or assembler
directive), an operand, and a comment.
 
 
2.2.1   Label Field
 
The label field occurs as the first field of a source statement. The
label field can take one of the following forms:
 
1. An asterisk (*) as the first character in the label field indicates
that the rest of the source statement is a comment. Comments are
ignored by the Assembler, and are printed on the source listing only
for the programmer's information.
 
2. A whitespace character (blank or tab) as the first character
indicates that the label field is empty. The line has no label and is
not a comment.
 
3. A symbol character as the first character indicates that the line
has a label. Symbol characters are the upper or lower case letters a-
z,  digits 0-9, and the special characters, period (.), dollar sign
($), and underscore (_). Symbols consist of one to 15 characters, the
first of which must be alphabetic or the special characters period (.)
or underscore (_).  All characters are significant and upper and lower
case letters are distinct.
 
A symbol may occur only once in the label field. If a symbol does
occur more than once in a label field, then each reference to that
symbol will be flagged with an error.
 
With the exception of some directives, a label is assigned the value
of the program counter of the first byte of the instruction or data
being assembled. The value assigned to the label is absolute.
Labels may optionally be ended with a colon (:).  If the colon is
used it is not part of the label but merely acts to set the label off
from the rest of the source line.  Thus the following code fragments
are equivalent:
 
     here:  deca
            bne here
 
 
 
                                 3
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
     here   deca
            bne here
 
A label may appear on a line by itself.  The assembler interprets this
as set the value of the label equal to the current value of the
program counter.
 
The symbol table has room for at least 2000 symbols of length 8
characters or less.  Additional characters up to 15 are permissible at
the expense of decreasing the maximum number of symbols possible in
the table.
 
 
2.2.2   Operation Field
 
The operation field occurs after the label field, and must be preceded
by at least one whitespace character. The operation field must contain
a legal opcode mneumonic or an assembler directive.  Upper case
characters in this field are converted to lower case before being
checked as a legal mneumonic.  Thus 'nop', 'NOP', and 'NoP' are
recognized as the same mneumonic. Entries in the operation field may
be one of two types:
 
Opcode. These correspond directly to the machine instructions. The
operation code includes any register name associated with the
instruction.  These register names must not be separated from the
opcode with any whitespace characters.  Thus 'clra' means clear
accumulator A, but 'clr a' means clear memory location identified by
the label 'a'.
 
Directive. These are special operation codes known to the Assembler
which control the assembly process rather than being translated into
machine instructions.
 
 
2.2.3   Operand Field
 
The operand field's interpretation is dependent on the contents of the
operation field. The operand field, if required, must follow the
operation field, and must be preceded by at least one whitespace
character. The operand field may contain a symbol, an expression, or a
combination of symbols and expressions separated by commas.
 
The operand field of machine instructions is used to specify the
addressing mode of the instruction, as well as the operand of the
instruction.   The following tables summarize the operand field
formats for the various processor families. (NOTE:  in these tables
parenthesis "()" signify optional elements and angle brackets "<>"
denote an expression is inserted.  These syntax elements are present
only for clarification of the format and are not inserted as part of
the actual source program.  All other characters are significant and
must be used when required.)
 
 
 
 
 
 
                                 4
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
2.2.3.1  M6800/6801 Operand Syntax
 
The format of the operand field for M6800/6801 instructions is:
 
     Operand Format           M6800/M6801 Addressing Mode
     --------------           ---------------------------
     no operand               accumulator and inherent
     <expression>             direct, extended, or relative
     #<expression>            immediate
     <expression>,X           indexed
 
Details of the M6800/6801 addressing modes may be found in Appendix B.
 
 
2.2.3.2  M6804/68HC Operand Syntax
 
For the M6804/68HC04, the following operand formats exist:
 
     Operand Format                M6804/68HC04 Addressing Mode
     --------------                ----------------------------
     no operand                    accumulator and inherent
     <expression>                  direct, extended, or relative
     #<expression>                 immediate
     <expression>                  bit set or clear
     <expression>,<expression>     bit test and branch
     [<x> or <y>]                  register indirect
     <expression>,#<expression>    move indirect
 
Details of the M6804/68HC04 addressing modes may be found in Appendix
B.
 
 
2.2.3.3  M6805/M68HC05 Operand Syntax
 
For the M6805/68HC05, the operand formats are:
 
     Operand Format                M6805/68HC05 Addressing Mode
     --------------                ----------------------------
     no operand                    accumulator and inherent
     <expression>                  direct, extended, or relative
     #<expression>                 immediate
     <expression>,X                indexed
     <expression>,<expression>     bit set or clear
     <expression>,<expression>,<expression>     bit test and branch
 
Details of the M6805/68HC05 addressing modes may be found in Appendix
B.
 
 
2.2.3.4  M6809 Operand Syntax
 
For the M6809, the following  operand formats are used:
 
 
 
 
 
 
                                 5
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
     Operand Format           M6809 Addressing Mode
     --------------           ---------------------
     no operand               accumulator and inherent
     <expression>             direct, extended, or relative
     #<expression>            immediate
     <expression>,X           indexed
     <<expression>            forced direct
     ><expression>            forced extended
     <expression>]            extended indirect
     <expression>,R           indexed
     <<expression>,R          forced 8-bit offset indexed
     ><expression>,R          forced 16-bit offset indexed
     [<expression>,R]         indexed indirect
     <[<expression>,R]        forced 8-bit offset indexed indirect
     >[<expression>,R]        forced 16-bit offset indexed indirect
     Q+                       auto increment by 1
     Q++                      auto increment by 2
     [Q++]                    auto increment indirect
     -Q                       auto decrement by
     --Q                      auto decrement by 2
     [--Q]                    auto decrement indirect
     W1,[W2,...,Wn]           immediate
 
where R is one of the registers PCR, S, U, X, or Y, and Q is one of
the registers S, U, X, or Y.   Wi  (i=1 to n) is one of the symbols A,
B, CC, D, DP, PC, S, U, X, or Y.
 
Details of the M6809 addressing modes may be found in Appendix B.
 
 
2.2.3.5  M68HC11 Operand Syntax
 
For the M68HC11, the following operand formats exist:
 
     Operand Format                M68HC11 Addressing Mode
     --------------                -----------------------
     no operand                    accumulator and inherent
     <expression>                  direct, extended, or relative
     #<expression>                 immediate
     <expression>,X                indexed with X register
     <expression>,Y                indexed with Y register
     <expression> <expression>     bit set or clear
     <expression> <expression> <expression>     bit test and branch
 
The bit manipulation instruction operands are separated by spaces in
this case since the HC11 allows bit manipulation instructions on
indexed addresses.  Thus a ',X' or ',Y' may be added to the final two
formats above to form the indexed effective address calculation.
 
Details of the M68HC11 addressing modes may be found in Appendix B.
The operand fields of assembler directives are described in Chapter 4.
 
 
2.2.3.6  Expressions.  An expression is a combination of symbols,
constants, algebraic operators, and parentheses. The expression is
used to specify a value which is to be used as an operand.
 
 
                                6
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
Expressions may consist of symbols, constants, or the character '*'
(denoting the current value of the program counter) joined together by
one of the operators: + - * / % & | ^ .
 
 
2.2.3.7  Operators.  The operators are the same as in c:
 
     +    add
     -    subtract
     *    multiply
     /    divide
     %    remainder after division
     &    bitwise and
     |    bitwise or
     ^    bitwise exclusive or
 
Expressions are evaluated left to right and there is no provision for
parenthesized expressions.  Arithmetic is carried out in signed two-
complement integer precision (that's 16 bits on the IBM PC).
 
 
2.2.3.8  Symbols.  Each symbol is associated with a 16-bit integer
value which is used in place of the symbol during the expression
evaluation.  The asterisk (*) used in an expression as a symbol
represents the current value of the location counter (the first byte
of a multi-byte instruction).
 
 
2.2.3.9  Constants.  Constants represent quantities of data that do
not vary in value during the execution of a program.  Constants may be
presented to the assembler in one of five formats: decimal,
hexadecimal, binary, or octal, or ASCII.  The programmer indicates the
number format to the assembler with the following prefixes:
 
     $    HEX
     %    BINARY
     @    OCTAL
     '    ASCII
 
Unprefixed constants are interpreted as decimal.  The assembler
converts all constants to binary machine code and are displayed in the
assembly listing as hex.
 
A decimal constant consists of a string of numeric digits. The value
of a decimal constant must fall in the range 0-65535, inclusive.  The
following example shows both valid and invalid decimal constants:
 
     VALID     INVALID   REASON INVALID
     -----     -------   --------------
     12        123456    more than 5 digits
     12345     12.3      invalid character
 
A hexadecimal constant consists of a maximum of four characters from
the set of digits (0-9) and the upper case alphabetic letters (A-F),
and is preceded by a dollar sign ($).  Hexadecimal constants must be
 
 
 
                                 7
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
in the range $0000 to $FFFF. The following example shows both valid
and invalid hexadecimal constants:
 
     VALID     INVALID   REASON INVALID
     -----     -------   --------------
     $12       ABCD      no preceding "$"
     $ABCD     $G2A      invalid character
     $001F     $2F018    too many digits
 
A binary constant consists of a maximum of 16 ones or zeros preceded
by a percent sign (%).  The following example shows both valid and
invalid binary constants:
 
     VALID     INVALID             REASON INVALID
     -----     -------             --------------
     %00101    1010101             missing percent
     %1        %10011000101010111  too many digits
     %10100    %210101             invalid digit
 
An octal constant consists of a maximum of six numeric digits,
excluding the digits 8 and 9, preceded by a commercial at-sign (@).
Octal constants must be in the ranges @0 to @177777.  The following
example shows both valid and invalid octal constan
ts:
 
     VALID     INVALID   REASON INVALID
     -----     -------   --------------
     @17634    @2317234  too many digits
     @377      @277272   out of range
     @177600   @23914    invalid character
 
A single ASCII character can be used as a constant in expressions.
ASCII constants are preceded by a single quote ('). Any character,
including the single quote, can be used as a character constant.   The
following example shows both valid and inval
id character constants:
 
     VALID     INVALID   REASON INVALID
     -----     -------   --------------
     '*        'VALID    too long
 
For the invalid case above the assembler will not indicate an error.
Rather it will assemble the first character and ignore the remainder.
 
 
2.2.4   Comment Field
 
The last field of an Assembler source statement is the comment field.
This field is optional and is only printed on the source listing for
documentation purposes. The comment field is separated from the
operand field (or from the operation field if no operand is required)
by at least one whitespace character. The comment field can contain
any printable ASCII characters.
 
 
 
 
 
                                 8
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
2.3   ASSEMBLER OUTPUT
 
The Assembler output includes an optional listing of the source
program and an object file which is in the Motorola S Record format.
Details of the S Record format may be found in Appendix E.   The
Assembler will normally suppress the printing of the source listing.
This condition, as well as others, can be overridden via options
supplied on the command line that invoked the Assembler.
 
Each line of the listing contains a reference line number, the address
and bytes assembled, and the original source input line.  If an input
line causes more than 6 bytes to be output (e.g. a long FCC
directive), additional bytes (up to 64) are listed on succeeding lines
with no address preceding them.
 
The assembly listing may optionally contain a symbol table or a cross
reference table of all symbols appearing in the program. These are
always printed at the end of the assembly listing if either the symbol
table or cross reference table options (Paragraph 4.8) are in effect.
The symbol table contains the name of each symbol, along with its
defined value. The cross reference table additionally contains the
assembler-maintained source line number of every reference to every
symbol. The format of the cross reference table is shown in Appendix
D.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                 9
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                              CHAPTER 3
                        RUNNING THE ASSEMBLERS
 
 
3.1   ASSEMBLER INVOCATION
 
The Motorola Freeware Assembly programs are named as*.exe where '*' is
any of 0, 1, 4, 5, 9, or 11 depending on which processor family you
wish to assemble code for.  For example, to generate M6800 code run
the as0.exe program.  To generate M68HC05 code run the as5.exe
program, and so forth.  To run the assembler enter the following
command line:
 
         as*   file1 (file2 . . . ) ( - option1 option2 . . . )
 
where file1, file2, etc are the names of the source files you wish to
assemble.  The source filenames may have extensions but the assembler
does not check for any particular extension ( however, do not use the
.S19 extension since that is the extension of the object file created
by the assembler.  Its creation would overwrite the source file when
it is written to the disk).
 
The options are one or more of the following:
 
     l    enables output listing
     no   disables output listing (default).
     cre  enables the cross reference table generation
     s    enables the symbol table generation
     c    enables cycle counting
     noc  disables cycle counting
 
The minus sign preceding the option should be separated from the last
file name by a space.  These options may also be indicated to the
assembler by the use of the OPT directive in the source file.  The OPT
directive is described in Paragraph 4.8.
 
The object file created is written to disk and given the name
'FILENAME.S19' where 'FILENAME' is the name of the first source file
specified on the command line.  Any errors and the optional listing
(if specified) are displayed on the screen.  The listing and/or error
messages may be saved to a file for later examination or printing by
append an i/o redirection command to the command line.  On the PC i/o
redirection is indicated with the greater-than ('>') symbol followed
by any new or existing file name.
 
Command line examples:
 
The command line
 
         as5 myfile
 
would run the M6805/68HC05 assembler on the source file 'myfile'.  The
object file would be written to 'myfile.s19' and any errors would
appear on the screen.
 
 
 
 
                                 10
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
The command line
 
         as9 test.asm nexttest.s -l
 
would run the M6809 assembler on the source files 'test.asm' and
'nexttest.s'.  The object file would be written to 'test.s19' and any
errors and the assembly listing would appear on the screen.
 
The command line
 
         as9 test.asm nexttest.s -l cre s >test.lst
 
would run the M6809 assembler on the source files 'test.asm' and
'nexttest.s'.  The object file would be written to 'test.s19'.  A
listing would be created followed by a symbol table and cross
reference which would all be written to the file test.lst
.
 
3.2   ERROR MESSAGES
 
Error diagnostic messages are placed in the listing file just before
the line containing the error.  The format of the error line is:
 
             Line_number:   Description of error
 
                                  or
 
             Line_number:   Warning ---- Description of error
 
Errors in pass one cause cancellation of pass two.  Warning do not
cause cancellation of pass two but are indications of a possible
problem.  Error messages are meant to be self-explanatory.
 
If more than one file is being assembled, the file name precedes the
error:
 
             File_name,Line_number:  Description of error
 
Some errors are classed as fatal and cause an immediate termination of
the assembly.  Generally this happens when a temporary file cannot be
created or is lost during assembly.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                11
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                              CHAPTER 4
                         ASSEMBLER DIRECTIVES
 
 
4.1   INTRODUCTION
 
The Assembler directives are instructions to the Assembler, rather
than instructions to be directly translated into object code. This
chapter describes the directives that are recognized by the Freeware
Assemblers. Detailed descriptions of each directive are arranged
alphabetically. The notations used in this chapter are:
 
  ( )  Parentheses denote an optional element.
 
  XYZ  The names of the directives are printed in capital letters.
 
  < >  The element names are printed in lower case and contained in
angle brackets.  All elements outside of the angle brackets '<>' must
be specified as-is. For example, the syntactical element (<number>,)
requires the comma to be specified if the optional element <number> is
selected. The following elements are used in the subsequent
descriptions:
 
 
     <comment>      A statement's comment field
     <label>        A statement label
     <expression>   An Assembler expression
     <expr>         An Assembler expression
     <number>       A numeric constant
     <string>       A string of ASCII characters
     <delimiter>    A string delimiter
     <option>       An Assembler option
     <symbol>       An Assembler symbol
     <sym>          An Assembler symbol
     <sect>         A relocatable program section
     <reg list>     M6809 register list
     <reg exp>      M6809 register expression
 
 
In the following descriptions of the various directives, the syntax,
or format, of the directive is given first.  This will be followed
with the directive's description.
 
4.2   BSZ - BLOCK STORAGE OF ZEROS
 
                   (<label>) BSZ <expression> (<comment>)
 
The BSZ directive causes the Assembler to allocate a block of bytes.
Each byte is assigned the initial value of zero. The number of bytes
allocated is given by the expression in the operand field. If the
expression contains symbols that are either undefined or forward
referenced (i.e. the definition occurs later on in the file), or if
the expression has a value of zero, an error will be generated.
 
 
 
 
 
                                 12
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
4.3   EQU - EQUATE SYMBOL TO A VALUE
 
                   <label> EQU <expression> (<comment>)
 
The EQU directive assigns the value of the expression in the operand
field to the label. The EQU directive assigns a value other than the
program counter to the label. The label cannot be redefined anywhere
else in the program.  The expression cannot contain any forward
references or undefined symbols.  Equates with forward references are
flagged with Phasing Errors.
 
4.4   FCB - FORM CONSTANT BYTE
 
         (<label>) FCB <expr>(,<expr>,...,<expr>) (<comment>)
 
The FCB directive may have one or more operands separated by commas.
The value of each operand is truncated to eight bits, and is stored in
a single byte of the object program.  Multiple operands are stored in
successive bytes. The operand may be a numeric constant, a character
constant, a symbol, or an expression. If multiple operands are
present, one or more of them can be null (two adjacent commas), in
which case a single byte of zero will be assigned for that operand.
An error will occur if the upper eight bits of the evaluated operands'
values are not all ones or all zeros.
 
4.5   FCC - FORM CONSTANT CHARACTER STRING
 
         (<label>) FCC <delimiter><string><delimiter> (<comment>)
 
The FCC  directive is used to store ASCII strings into consecutive
bytes of memory.  The byte storage begins at the current program
counter.  The label is assigned to the first byte in the string. Any
of the printable ASCII characters can be contained in the string.  The
string is specified  between two identical delimiters which can be any
printable ASCII character. The first non-blank character after the FCC
directive is used as the delimiter.
 
Example:
 
     LABEL1    FCC  , ABC,
 
assembles ASCII ABC at location LABEL1
 
 
4.6 FDB - FORM DOUBLE BYTE CONSTANT
 
         (<label>) FDB <expr>(,<expr>,...,<expr>) (<comment>)
 
The FDB directive may have one or more operands separated by commas.
The 16-bit value corresponding to each operand is stored into two
consecutive bytes of the object program.  The storage begins at the
current program counter.  The label is assigned to the first 16-bit
value. Multiple operands are stored in successive bytes.  The operand
may be a numeric constant, a character constant, a symbol, or an
expression. If multiple operands are present, one or more of them can
 
 
 
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                                   Freeware Assemblers User's Manual
 
 
be null (two adjacent commas), in which case two bytes of zeros will
be assigned for that operand.
 
4.7 FILL - FILL MEMORY
 
                   (<label>) FILL <expression>,<expression>
 
The FILL directive causes the assembler to initialize an area of
memory with a constant value.  The first expression signifies the one
byte value to be placed in the memory and the second expression
indicates the total number of successive bytes to be initialized.  The
first expression must evaluate to the range 0-255.  Expressions cannot
contain forward references or undefined symbols.
 
4.8 OPT - ASSEMBLER OUTPUT OPTIONS
 
         OPT <option>(,<option>,...,<option>) (<comment>)
 
The OPT directive is used to control the format of the Assembler
output. The options are specified in the operand field, separated by
commas. All options have a default condition.  Some options can be
initialized from the command line that invoked the Assembler, however
the options contained in the source file take precedence over any
entered on the command line. In the following descriptions, the
parenthetical inserts specify "DEFAULT", if the option is the default
condition.  All options must be entered in lower case.
 
  c -  Enable cycle counting in the listing.  The total cycle count
for that instruction will appear in the listing after the assembled
bytes and before the source code.
 
  cre -  Print a cross reference table at the end of the source
listing. This option, if used, must be specified before the first
symbol in the source program is encountered.  The cross reference
listing format may be found in Appendix D.
 
   l -  Print the listing from this point on.  A description of the
listing format can be found in Appendix D.
 
   noc -  (DEFAULT) Disable cycle counting in the listing.  If the "c"
option was used previously in the program, this option will cause
cycle counting to cease until the next "OPT c" statement.
 
  nol -   (DEFAULT)  Do not print the listing from this point on.  An
"OPT l" can re-enble listing at a later point in the program.
 
   s -  Print symbol table at end of source listing.  The symbol table
format can be found in Appendix D.
 
 
4.9 ORG - SET PROGRAM COUNTER TO ORIGIN
 
                   ORG <expression> (<comment>)
 
The ORG directive changes the program counter to the value specified
by the expression in the operand field. Subsequent statements are
 
 
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                                   Freeware Assemblers User's Manual
 
 
assembled into memory locations starting with the new program counter
value. If no ORG directive is encountered in a source program, the
program counter is initialized to zero.  Expressions cannot contain
forward references or undefined symbols.
 
 
4.10 PAGE - TOP OF PAGE
 
                   PAGE
 
The PAGE directive causes the Assembler to advance the paper to the
top of the next page. If no source listing is being produced, the PAGE
directive will have no effect. The directive is not printed on the
source listing.
 
 
4.11 RMB - RESERVE MEMORY BYTES
 
                (<label>) RMB <expression> (<comment>)
 
The RMB directive causes the location counter to be advanced by the
value of the expression in the operand field. This directive reserves
a block of memory the length of which in bytes is equal to the value
of the expression. The block of memory reserved is not initialized to
any given value. The expression cannot contain any forward references
or undefined symbols.  This directive is commonly used to reserve a
scratchpad or table area for later use.
 
4.12 ZMB - ZERO MEMORY BYTES  (same as BSZ)
 
                  (<label>) ZMB <expression> (<comment>)
 
The ZMB directive causes the Assembler to allocate a block of bytes.
Each byte is assigned the initial value of zero. The number of bytes
allocated is given by the expression in the operand field. If the
expression contains symbols that are either undefined or forward
references, or if the expression has a value of zero, an error will be
generated.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                 15
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                               APPENDIX A
                              CHARACTER SET
 
 
The character set recognized by the Freeware Assemblers is a subset of
ASCII. The ASCII code is shown in the following figure. The following
characters are recognized by the Assembler:
 
        1. The upper case letters A through Z and lower case letters a
           through z.
 
        2. The digits 0 through 9.
 
        3. Five arithmetic operators:  +, -, *, / and % (remainder
           after division).
 
        4. Three logical operators:  &, |, and ^.
 
        5. The special symbol characters:  underscore (_), period (.),
           and dollar sign ($).  Only the underscore and period may be
           used as the first character of a symbol.
 
        6. The characters used as prefixes for constants and
           addressing modes:
 
               #    Immediate addressing
               $    Hexadecimal constant
               &    Decimal constant
               @    Octal constant
               %    Binary constant
               '    ASCII character constant
 
        7. The characters used as suffixes for constants and
           addressing modes:
 
               ,X   Indexed addressing
               ,PCR M6809 indexed addressing
               ,S   M6809 indexed addressing
               ,U   M6809 indexed addressing
               ,Y   M6809 and M68HC11 indexed addressing
 
        8. Three separator characters:  space, carriage return, and
           comma.
 
        9. The character "*" to indicate comments.  Comments may
           contain any printable characters from the ASCII set.
 
       10. The special symbol backslash "\" to indicate line
           continuation.  When the assembler encounters the line
           continuation character it fetches the next line and adds it
           to the end of the first line.  This continues until a line
           is seen which doesn't end with a backslash or until the
           system maximum buffer size has been collected (typically
           greater or equal to 256).
 
 
 
 
                                16
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
       11. For the M6809 Assembler, the character "<" preceding an
           expression to indicate direct addressing mode or 8-bit
           offset in indexed mode, and the character ">" preceding an
           expression to indicate extended addressing mode or 16-bit
           offset in indexed mode.
 
      12. For the M6809 Assembler, the characters used to indicate
          auto increment and auto decrement in the indexed mode:  +,
          ++, -, --.
 
 
 
 
                         ASCII CHARACTER CODES
 
 
           BITS 4 to 6 -- 0    1    2    3    4    5    6    7
           -----------    -------------------------------------
 
 
                B    1    SOH  DC1  :    1    A    Q    a    q
                I    2    STX  DC2  !    2    B    R    b    r
                T    3    ETX  DC3  #    3    C    S    c    s
                S    4    EOT  DC4  $    4    D    T    d    t
                     5    ENQ  NAK  %    5    E    U    e    u
 
                     7    BEL  ETB  '    7    G    W    g    w
                T    8    BS   CAN  (    8    H    X    h    x
                O    9    HT   EM   )    9    I    Y    i    y
                     A    LF   SUB  *    :    J    Z    j    z
                3    B    VT   ESC  +    ;    K    [    k    {
                     C    FF   FS   ,    <    L    \    l    ;
                     D    CR   GS   -    =    M    ]    m    }
                     E    SO   RS   .    >    N    ^    n    ~
                     F    S1   US   /    ?    O    _    o    DEL
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                17
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                              APPENDIX B
                           ADDRESSING MODES
 
B.1   M6800/M6801 ADDRESSING MODES.
 
INHERENT OR ACCUMULATOR ADDRESSING
The M6800 includes some instructions which require no operands. These
instructions are self-contained and employ the inherent addressing or
the accumulator addressing mode.
 
 
IMMEDIATE ADDRESSING
Immediate addressing refers to the use of one or two bytes of
information that immediately follow the operation code in memory.
Immediate addressing is indicated by preceding the operand field with
the pound sign or number sign character (#). The expression following
the # will be assigned one or two bytes of storage, depending on the
instruction.
 
 
RELATIVE ADDRESSING
Relative addressing is used by branch instructions. Branches can only
be executed within the range -126 to +129 bytes relative to the first
byte of the branch instruction.  For this mode, the programmer
specifies the branch address expression and places it in the operand
field. The actual branch offset is calculated by the assembler and put
into the second byte of the branch instruction.  The offset is the
two's complement of the difference between the location of the byte
immediately following the branch instruction and the location of the
destination of the branch.  Branches out of bounds are flagged as
errors by the assembler.
 
 
INDEXED ADDRESSING
Indexed addressing is relative to the index register. The address is
calculated at the time of instruction execution by adding a one-byte
displacement (in the second byte of the instruction) to the current
contents of the X register. Since no sign extension is performed on
this one-byte displacement, the offset cannot be negative. Indexed
addressing is indicated by the characters ",X" following the
expression in the operand field. The special case of ",X", without a
preceding expression, is treated as "0,X".
 
 
DIRECT AND EXTENDED ADDRESSING
Direct and extended addressing utilize one (direct) or two (extended)
bytes to contain the address of the operand. Direct addressing is
limited to the first 256 bytes of memory. Direct and extended
addressing are indicated by only having an expression in the operand
field. Direct addressing will be used by the Assembler whenever
possible.
 
 
 
 
 
 
 
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                                   Freeware Assemblers User's Manual
 
 
B.2   M6804/M68HC04 ADDRESSING MODES.
 
INHERENT OR ACCUMULATOR ADDRESSING
The M6800 includes some instructions which require no operands. These
instructions are self-contained and employ the inherent addressing or
the accumulator addressing mode.
 
 
IMMEDIATE ADDRESSING
Immediate addressing refers to the use of one byte of information that
immediately follows the operation code in memory. Immediate addressing
is indicated by preceding the operand field with the pound sign or
number sign character (#). The expression following the # will be
assigned one byte of storage.
 
 
RELATIVE ADDRESSING
Relative addressing is used by branch instructions. Branches can only
be executed within the range -15 to +16 bytes relative to the first
byte of the branch instruction.  For this mode, the programmer
specifies the branch address expression and places it in the operand
field. The actual branch offset is calculated by the assembler and put
into the second byte of the branch instruction.  The offset is the
two's complement of the difference between the location of the byte
immediately following the branch instruction and the location of the
destination of the branch.  Branches out of bounds are flagged as
errors by the assembler.
 
 
DIRECT AND EXTENDED ADDRESSING
Direct and extended addressing utilize byte to contain the address of
the operand. Direct addressing is limited to the first 256 bytes of
memory.  Extended addressing concatenates the four least-significant
bits of the opcode with the byte following the opcode to form a 12-bit
address. Direct and extended addressing are indicated by only having
an expression in the operand field.  Direct addressing will be used by
the Assembler whenever possible.
 
 
SHORT DIRECT
Some opcodes allow 4 memory locations in data space ram ($80, $81,
$82, and $83 to be referenced as part of the opcode.  The opcode
determines the data space RAM location, and the instruction is only
one byte.  The X and Y registers are at locations $80 and $81,
respectively.   An expression used with short direct addressing must
not be forward referenced (that is its definition must occur before,
not after this point in the file) and must equate to the range $80-
$83.
 
 
BIT SET AND CLEAR
In the bit set/clear addressing mode, the bit to be set or cleared is
part of the opcode.  The byte following the opcode specifies the
direct address of the byte which will have the bit set or cleared.
Any bit in the 256 byte data space memory that can be written (with
 
 
 
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                                   Freeware Assemblers User's Manual
 
 
the exception of the data direction registers) can be set or cleared
with these two byte instructions.
 
 
BIT TEST AND BRANCH
The bit test and branch addressing mode is a combination of the direct
addressing and relative addressing.  The bit to be tested, and it
condition (set or clear), is included in the opcode.  The data space
address of the byte to be tested is in the single byte immediately
following the opcode byte and follows direct addressing rules.  The
third byte is sign extended by the processor during execution to form
the 12-bit relative address which is added to the program counter if
the condition is true.  This allows branches based on any readable bit
in the data space.  The branch span is -125 to +130 from the opcode
address.  The branch target address is used by the programmer to
signify the relative offset -- the assembler calculates the offset
value.  Branches out of bounds are flagged as errors by the
assembler.
 
 
REGISTER INDIRECT
In the register indirect mode, the operand is at the address in data
space pointed to by the contents of one of the indirect registers, X
or Y.  The particular indirect register is encoded in bit 4 of the
opcode by the assembler.  The assembler  operand syntax for register
indirect is
 
                    [<X> or <Y>]
 
 
MOVE IMMEDIATE
The MVI (move immediate) instruction has its own format:
 
         mvi   <expression 1>,#<expression 2>
 
where <expression 1> is a direct address and <expression 2> is the
data value to be written.
 
 
MISCELLANEOUS SYNTAX ISSUES
The registers in the 6804/HC6804 are memory locations and have
addresses assigned to them.  The assembler has predefined
 
           a = A = $FF
           b = B = $80
           c = C = $81
 
This also means that for the '04 assembler clr x is equivalent to clrx
since x is both a register and a memory location.
 
The '04 series has separate program and data spaces.  There is no
program memory in the range $10-$7F.  Bytes assembled into that range
will go into the data space.
 
 
 
 
 
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B.3   M6805/68HC05 ADDRESSING MODES.
 
INHERENT OR ACCUMULATOR ADDRESSING
The M6805 includes some instructions which require no operands. These
instructions are self-contained, and employ the inherent addressing or
the accumulator addressing mode.
 
 
IMMEDIATE ADDRESSING
Immediate addressing refers to the use of one byte of information that
immediately follows the operation code in memory. Immediate addressing
is indicated by preceding the operand field with the pound sign or
number sign character (#). The expression following the # will be
assigned one byte of storage.
 
 
RELATIVE ADDRESSING
Relative addressing is used by branch instructions. Branches can only
be executed within the range -126 to +129 bytes relative to the first
byte of the branch instruction. For this mode, the programmer
specifies the branch address expression and places it in the operand
field. The actual branch offset is calculated by the assembler and put
into the second byte of the branch instruction.  The offset is the
two's complement of the difference between the location of the byte
immediately following the branch instruction and the location of the
destination of the branch.  Branches out of bounds are flagged as
errors by the assembler.
 
 
INDEXED ADDRESSING
Indexed addressing is relative to the index register. The address is
calculated at the time of instruction execution by adding a one- or
two-byte displacement to the current contents of the X register. The
displacement immediately follows the operation code in memory.  If the
displacement is zero, no offset is added to the index register.  In
this case, only the operation code resides in memory.  Since no sign
extension is performed on a one-byte displacement, the offset cannot
be negative. Indexed addressing is indicated by the characters ",X"
following the expression in the operand field.  The special case of
",X", without a preceding expression, is treated as "0,X". Some
instructions do not allow a two-byte displacement.
 
 
DIRECT AND EXTENDED ADDRESSING
Direct and extended addressing utilize one (direct) or two (extended)
bytes to contain the address of the operand. Direct addressing is
limited to the first 256 bytes of memory.  Direct and extended
addressing are indicated by only having an expression in the operand
field. Some instructions do not allow extended addressing.  Direct
addressing will be used by the Macro Assembler whenever possible.
 
 
BIT SET OR CLEAR
The addressing mode used for this type of instruction is direct,
although the format of the operand field is different from the direct
addressing mode described above. The operand takes the form
 
 
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                                   Freeware Assemblers User's Manual
 
 
<expression 1>, <expression 2>. <expression 1> indicates which bit is
to be set or cleared.  It must be an absolute expression in the range
0-7. It is used in generating the operation code.  <expression 2> is
handled as a direct address, as described above.  Since the bit
manipulation address is direct, only the first 256 locations may be
operated on by bit manipulation operations.
 
 
BIT TEST AND BRANCH
This combines two addressing modes: direct and relative. The format of
the operand is: <expression 1>, <expression 2>, <expression 3>.
<expression 1> and <expression 2> are handled in the same manner as
described above in "bit set or clear". <expression 3> is used to
generate a relative address, as described above in "relative
addressing".
 
 
B.4  M6809 ADDRESSING MODES.
 
INHERENT OR ACCUMULATOR ADDRESSING
The M6809 includes some instructions which require no operands. These
instructions are self-contained, and employ the inherent addressing or
the accumulator addressing mode.
 
 
IMMEDIATE ADDRESSING
Immediate addressing refers to the use of one or two bytes of
information that immediately follow the operation code in memory.
Immediate addressing is indicated by preceding the operand field with
the pound sign or number sign (#) -- i.e., #<expression>.  The
expression following the # will be assigned one or two bytes of
storage, depending on the instruction. All instructions referencing
the accumulator "A" or "B", or the condition code register "CC", will
generate a one-byte immediate value. Also, immediate addressing used
with the PSHS, PULS, PSHU, and PULU instructions generates a one-byte
immediate value. Immediate operands used in all other instructions
generate a two-byte value.
 
The register list operand does not take the form #<expression> but
still generates one byte of immediate data. The form of the operand
is:
 
                            R1,R2,...,Rn
 
where Ri (i=1 to n)  is one of the symbols A, B, CC, D, DP, PC, S, U,
X or Y. The number and type of symbols vary, depending on the specific
instruction.
 
For the instructions PSHS, PULS, PSHU, and PULU, any of the above
register names may be included in the register list. The only
restriction is that "U" cannot be specified with PSHU or PULU, and "S"
cannot be specified with PSHS  or PULS. The one-byte immediate value
assigned to the operand is calculated by the assembler and is
determined by the registers specified. Each register name causes the
assembler to set a bit in the immediate byte as follows:
 
 
 
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                                   Freeware Assemblers User's Manual
 
 
          Register  Bit
          --------  ---
 
            PC      7
            U,S     6
            Y       5
            X       4
            DP      3
            B,D     2
            A,D     1
            CC      0
 
 
For the instructions EXG and TFR, exactly two of the above register
names must be included in the register list. The other restriction is
the size of the registers specified. For the EXG instruction, the two
registers must be the same size. For the TFR instruction, the two
registers must be the same size, or the first can be a 16-bit register
and the second an 8-bit register. In the case where the transfer is
from a 16-bit register to an 8-bit register, the least significant 8
bits are transferred.  The 8-bit registers are A, B, CC, and DP.  The
16-bit registers are D, PC, S, U, X, and Y.  The one-byte immediate
value assigned to the operand by the assembler is determined by the
register names. The most significant four bits of the immediate byte
contain the value of the first register name; the least significant
four bits contain the value of the second register, as shown by the
following table:.
 
 
          Register  Value (hex)
          --------  -----------
 
             D          0
             X          1
             Y          2
             U          3
             S          4
             PC         5
             A          8
             B          9
             CC         A
             DP         B
 
 
RELATIVE  ADDRESSING
Relative addressing is used by branch instructions. There are two
forms of the branch instruction. The short branch can only be executed
within the range -126 to +129 bytes relative to the first byte of the
branch instruction. For this mode, the programmer specifies the branch
address expression and places it in the operand field. The actual
branch offset is calculated by the assembler and put into the second
byte of the branch instruction. The long branch can execute in the
full range of addressing from 0000-FFFF (hexadecimal) because a two-
byte offset is calculated by the assembler and put into the operand
field of the branch instruction.  The offset is the two's complement
of the difference between the location of the byte immediately
 
 
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following the branch instruction and the location of the destination
of the branch.
 
 
DIRECT AND EXTENDED ADDRESSING
Direct and extended addressing utilize one (direct) or two (extended)
bytes to contain the address of the operand. Direct and extended
addressing are indicated by having only an expression in the operand
field (i.e., <expression>). Direct addressing will be used whenever
possible.
 
Regardless of the criteria described above, it is possible to force
the Assembler to use the direct addressing mode by preceding the
operand with the "<" character. Similarly, extended addressing can be
forced by preceding the operand with the ">" character.  These two
operand forms are: <<expression> and ><expression>.
 
 
INDEXED ADDRESSING
Indexed addressing is relative to one of the index registers. The
general form is <expression>,R. The address is calculated at the time
of instruction execution by adding the value of <expression> to the
current contents of the index register. The other general form is
[<expression>,R].   In this indirect form, the address is calculated
at the time of instruction execution by first adding the value of
<expression> to the current contents of the index register, and then
retrieving the two bytes from the calculated address and address+1.
This two-byte value is used as the effective address of the operand.
The allowable forms of indexed addressing are described below.  In the
description below, R refers to one of the index registers S, U, X, or
Y.
 
The accumulator offset mode allows one of the accumulators to be
specified instead of an <expression>. Valid forms are:.
 
                   <acc>,R and [<acc>,R]
 
where <acc>  is one of the accumulators A, B, or D. This form
generates a one-byte operand (post-byte only). When accumulator A or B
is specified, sign extension occurs prior to adding the value in the
accumulator to the index register.
 
The valid forms for the automatic increment/decrement mode are shown
below.  For each row, the three entries shown are equivalent.
 
 
               R+       ,R+      0,R+
               -R       ,-R      0,-R
               R++      ,R++     0,R++
               --R      ,--R     0,--R
               [R++]    ,R++]    [0,R++]
               [--R]    [,--R]   [0,--R]
 
 
In this form, the only valid expression is 0. Like the accumulator
offset mode, this form generates a one-byte operand (post-byte only).
 
 
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                                   Freeware Assemblers User's Manual
 
 
The valid forms for the expression offset mode are:
 
 
               R       ,R     <expression>,R
               [R]     [,R]   [<expression>,R]
               <R      <,R    <<expression>,R
               <[R]    <[,R]  <[<expression>,R]
               >R      >,R    ><expression>,R
               >[R]    >[,R]  >[<expression>,R]
 
 
The "<" and ">" characters force an 8- or 16-bit offset, respectively,
and are described below. If no expression is specified, or if an
expression with a value of zero is specified, only the postbyte of
the operand is generated. If an expression with a value in the range
-16 to +15 is specified without indirection, a one- byte operand is
generated which contains the expression's value, as well as the index
register indicator. At execution time, the expression's value is
expanded to 16 bits with sign extension before being added to the
index register.
 
All other forms will generate a post-byte, as well as either a one- or
two-byte offset which contains the value of the expression. The size
of the offset is determined by the type and size of the expression.
Expressions with values in the range -128 to +127 generate an 8-bit
offset.   All other cases will result in a 16-bit offset being
generated. In the case where an 8-bit offset is generated, the value
is expanded to 16 bits with sign extension at execution time.
 
Regardless of the criteria described above, it is possible to force
the Assembler to generate an 8-bit offset by preceding the operand
with the "<" character. Similarly, a 16-bit offset can be forced by
preceding the operand with the ">" character.
 
If the relative address calculated is not in the range -128 to +127,
or if the expression references a symbol that has not yet been
defined, a two-byte offset is generated after the post-byte. A one-
byte offset is generated if the relative address is in the range -128
to +127.
 
Like the expression offset mode, a one-byte offset can be forced by
preceding the operand with a "<".  A ">" forces a two-byte offset. A
byte overflow error is generated if a one-byte offset is forced when
the relative address is not in the range -12
8 to +127.
 
The extended indirect mode has the form:
 
                     [<expression>]
 
Although extended indirect is a logical extension of the extended
addressing mode, this mode is implemented using an encoding of the
postbyte under the indexed addressing mode.  A post-byte and a two-
byte offset which contains the value of the expression is generated.
 
 
 
 
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B.5  M68HC11 ADDRESSING MODES.
 
PREBYTE
The number of combinations of instructions and addressing modes for
the 68HC11 is larger than that possible to be encoded in an 8-bit word
(256 combinations).  To expand the opcode map, certain opcodes ($18,
$1A, and $CD) cause the processor to fetch the next address to find
the actual instruction.  These opcodes are known as prebytes and are
inserted automatically by the assembler for those instructions that
require it.l  In general the instructions contained in the alternate
maps are those involving the Y register or addressing modes that
involve the Y index register.  Thus the programmer make the tradeoff
between the convenience of using the second index register and the
additional time and code space used by the prebyte.
 
 
INHERENT OR ACCUMULATOR ADDRESSING
The M68HC11 includes some instructions which require no operands.
These instructions are self-contained, and employ the inherent
addressing or the accumulator addressing mode.
 
 
IMMEDIATE ADDRESSING
Immediate addressing refers to the use of one or more bytes of
information that immediately follow the operation code in memory.
Immediate addressing is indicated by preceding the operand field with
the pound sign or number sign character (#). The expression following
the # will be assigned one byte of storage.
 
 
RELATIVE ADDRESSING
Relative addressing is used by branch instructions. Branches can only
be executed within the range -126 to +129 bytes relative to the first
byte of the branch instruction. For this mode, the programmer
specifies the branch address expression and places it in the operand
field. The actual branch offset is calculated by the assembler and put
into the second byte of the branch instruction.  The offset is the
two's complement of the difference between the location of the byte
immediately following the branch instruction and the location of the
destination of the branch.  Branches out of bounds are flagged as
errors by the assembler.
 
 
INDEXED ADDRESSING
Indexed addressing is relative one of the index registers X or Y.  The
address is calculated at the time of instruction execution by adding a
one-byte displacement to the current contents of the X register. The
displacement immediately follows the operation code in memory.  If the
displacement is zero, zero resides in the byte following the opcode.
Since no sign extension is performed on a one-byte displacement, the
offset cannot be negative. Indexed addressing is indicated by the
characters ",X" following the expression in the operand field.  The
special case of ",X", without a preceding expression, is treated as
"0,X".
 
 
 
 
                                26
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
DIRECT AND EXTENDED ADDRESSING
Direct and extended addressing utilize one (direct) or two (extended)
bytes to contain the address of the operand. Direct addressing is
limited to the first 256 bytes of memory.  Direct and extended
addressing are indicated by only having an expression in the operand
field.  Direct addressing will be used by the Assembler whenever
possible.
 
 
BIT(S) SET OR CLEAR
The addressing mode used for this type of instruction is direct,
although the format of the operand field is different from the direct
addressing mode described above. The operand takes the form
<expression 1> <expression 2> where the two expressions are separated
by a blank.   <expression 1> signifies the operand address and may be
either a direct or an indexed address.  When the address mode is
indexed, <expression  1> is followed by ',R' where R is either X or Y.
This allows bit manipulation instructions to operate across the
complete 64K address map.  <expression 2> is the mask byte.  The
bit(s) to be set or cleared are indicated by ones in the corresponding
location(s) in the mask byte.  The mask byte must be an expression in
the range 0-255 and is encoded by the programmer.
 
 
BIT TEST AND BRANCH
This combines two addressing modes: direct or indexed and relative.
The format of the operand is: <expression 1> <expression 2>
<expression 3> where the expressions are separated by blanks.
<expression 1>  identifies the operand an may indicate either a direct
or indexed address.  Indexed addresses are signified with ',R'
following the expression where R is either X or Y. <expression 2> is
the mask byte.  The bit(s) to be set or cleared are indicated by ones
in the corresponding location(s) in the mask byte.  The mask byte must
be an expression in the range 0-255 and is encoded by the programmer.
<expression 3> is used to generate a relative address, as described
above in "relative addressing".
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                27
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                               APPENDIX C
                            DIRECTIVE SUMMARY
 
 
A complete description of all directives appears in Chapter 4.
 
 
ASSEMBLY CONTROL
 
     ORG  Origin program counter
 
SYMBOL DEFINITION
 
     EQU  Assign permanent value
 
DATA DEFINITION/STORAGE ALLOCATION
 
     BSZ  Block storage of zero; single bytes
 
     FCB  Form constant byte
 
     FCC  Form constant character string
 
     FDB  Form constant double byte
 
     FILL Initialize a block of memory to a constant
 
     RMB  Reserve memory; single bytes
 
     ZMB  Zero Memory Bytes; same and BSZ
 
 
 LISTING CONTROL
 
     OPT c     Enable cycle counting
 
     OPT cre   Print cross reference table
 
     OPT l     Print source listing from this point
 
     OPT nol   Inhibit printing of source listing from this point
 
     OPT s     Print symbol table
 
     PAGE Print subsequent statements on top of next page
 
 
 
 
 
 
 
 
 
 
 
 
 
                                28
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                              APPENDIX D
                        ASSEMBLER LISTING FORMAT
 
 
The Assembler listing has the following format:
 
    LINE#   ADDR  OBJECT CODE BYTES       [ # CYCLES]  SOURCE LINE
 
The LINE# is a 4 digit decimal number printed as a reference.  This
reference number is used in the cross reference.  The ADDR is the hex
value of the address for the first byte of the object code for this
instruction.   The OBJECT CODE BYTES are the assembled object code of
the source line in hex.  If an source line causes more than 6 bytes
to be output (e.g. a long FCC directive), additional bytes (up to 64)
are listed on succeeding lines with no address preceding them.
 
The # CYCLES will only appear in the listing if the "c" option is in
effect.  It is enclosed in brackets which helps distinguish it from
the source listing.  The SOURCE LINE is reprinted exactly from the
source program, including labels.
 
The symbol table has the following format:
 
     SYMBOL    ADDR
 
The symbol is taken directly from the label field in the source
program.  The ADDR is the hexadecimal address of the location
referenced by the symbol.
 
The cross reference listing has the following format:
 
     SYMBOL   ADDR   *LOC1 LOC2 LOC3 ...
 
The SYMBOL and ADDR are the same as above. The * indicates the start
of the line reference numbers.  The LOCs are the decimal line numbers
of the assembler listing where the label occurs.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                29
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
                              APPENDIX E
                         S-RECORD INFORMATION
 
 
E.1   INTRODUCTION
 
The S-record output format encodes program and data object modules
into a printable (ASCII) format.  This allows viewing of the object
file with standard tools and allows display of the module while
transferring from one computer to the next or during loads between a
host and target.  The S-record format also includes information for
use in error checking to insure the integrity of data transfers.
 
 
E.2   S-RECORD CONTENT
 
S-Records are character strings made of several fields which identify
the record type, record length, memory address, code/data, and
checksum.  Each byte of binary data is encoded as a 2-character
hexadecimal number:  the first character representing the high-order
4 bits, and the second the low-order 4 bits of the byte.
 
The 5 fields which comprise an S-record are:
 
      TYPE  RECORD LENGTH   ADDRESS   CODE/DATA  CHECKSUM
 
The fields are defined as follows:
 
     FIELD      CHARACTERS                   CONTENTS
     -----      ----------                   --------
     Type           2          S-record type - S1, S9, etc.
 
     Record         2          The count of the character pairs in the
     length                    record, excluding the type and record
                               length.
 
     Address      4, 6,        The 2-, 3-, or 4-byte address at which
                  or 8         the data field is to be loaded into
                               memory.
 
     Code/data    0-2n         From 0 to n bytes of executable code,
                               memory loadable data, or descriptive
                               information.
 
     Checksum       2          The least significant byte of the one's
                               complement of the sum of the values
                               represented by the pairs of characters
                               making up the record length, address,
                               and the code/data fields.
 
Each record may be terminated with a CR/LF/NULL.
 
 
E.3   S-RECORD TYPES
 
Eight types of s-records have been defined to accommodate various
 
 
                                30
 
 
 
 
                                   Freeware Assemblers User's Manual
 
 
encoding, transportation, and decoding needs.  The Freeware
assemblers use only two types, the S1 and S9:
 
     S1   A record containing code/data and the 2-byte
          address at which the code/data is to reside.
 
     S9   A termination record for a block of S1 records. The address
          field may optionally contain the 2-byte address of the
          instruction to which control is to be passed.  If not
          specified, the first entry point specifica
          tion encountered in the object module input will be used.
          There is no code/data field.
 
E.4   S-RECORD EXAMPLE
 
The following is a typical S-record module:
 
          S1130000285F245F2212226A000424290008237C2A
          S11300100002000800082629001853812341001813
          S113002041E900084E42234300182342000824A952
          S107003000144ED492
          S9030000FC
 
The module consists of four code/data records and an S9 termination
record.
 
The first S1 code/data record is explained as follows:
 
     S1   S-record type S1, indicating a code/data record to be
          loaded/verified at a 2-byte address.
 
     13   Hex 13 (decimal 19), indicating 19 character pairs,
          representing 19 bytes of  binary data, follow.
 
     00   Four-character 2-byte address field:  hex address 0000,
          indicates location where the following data is to be loaded.
 
     The next 16 character pairs are the ASCII bytes of the actual
     program code/data
 
     2A   Checksum of the first S1 record.
 
The second and third S1 code/data records each also contain $13
character pairs and are ended with checksums.  The fourth S1 code/data
record contains 7 character pairs.
 
The S9 termination record is explained as follows:
 
     S9   S-record type S9, indicating a termination record.
 
     03   Hex 03, indicating three character pairs (3 bytes) to
          follow.
 
     00   Four character 2-byte address field, zeroes.
     00
 
     FC   Checksum of  S9 record.
 
                                31
 
 
 
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