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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
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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 ASSEMBLER.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 formatting. (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.
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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 mnemonic 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 white space 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
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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 white space character. The operation field
must contain a legal opcode mnemonic or an assembler directive.
Upper case characters in this field are converted to lower case
before being checked as a legal mnemonic. Thus 'nop', 'NOP', and
'NoP' are recognized as the same mnemonic. 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 white space 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 white space
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.)
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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:
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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.
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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 twos
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
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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 constants:
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 invalid 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 white space character. The comment field can contain
any printable ASCII characters.
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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.
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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.
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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.
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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.
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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-enable 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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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.
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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).
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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
----------- -------------------------------------
0 NUL DLE SP 0 @ P ` p
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
0 6 ACK SYN & 6 F V f v
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
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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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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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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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<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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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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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".
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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".
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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
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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.
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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
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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 specification 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.
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