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|
<html>
<head>
<title>CASM - A simple, portable multi-pass assembler</title>
<style>
h1
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body
{
background-color: white;
color: black;
font-family: sans-serif;
font-weight: normal;
width: 80%;
margin: auto;
}
.legalise
{
font-variant: small-caps;
font-size: 80%;
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.codeblock
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width: 100%;
background-color: #e0e0ff;
padding: 5px;
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color: white;
white-space: nowrap;
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}
</style>
</head>
<body>
<div class="legalise">
<p><b>casm</b> is a simple, portable multi-pass assembler</p>
<p>Copyright (C) 2003-2024 Ian Cowburn</p>
<p>This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.</p>
<p>This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.</p>
<p>You should have received a copy of the GNU General Public License
along with this program. If not, see
<a href="http://www.gnu.org/licenses/gpl-3.0.html">
http://www.gnu.org/licenses/gpl-3.0.html)</a></p>
</div>
<h1>Index</h1>
<p>
<a href="#casm">CASM</a> - General usage
</p>
<p>
<a href="#z80">Z80</a> - Z80 processor support.
</p>
<p>
<a href="#6502">6502</a> - 6502 processor support.
</p>
<p>
<a href="#gbcpu">Gameboy Z80</a> - The Gameboy Z80 derivative processor.
</p>
<p>
<a href="#65c816">65c816</a> - 65c816 processor support, as used in the SNES.
</p>
<p>
<a href="#spc700">SPC700</a> - SPC700 processor support, as used in the SNES
sound co-processor.
</p>
<h1 id="casm">CASM</h1>
<h2>Usage</h2>
<div class="codeblock">
casm <i>file</i>
</div>
<p>Assembles <i>file</i>, and places the resulting code in a file called
<b>output</b> by default.</p>
<p>Note that switches aren't used by <b>casm</b>. Instead options are
controlled by commands in the source <i>file</i>.</p>
<p>If you type the command without an argument, usage, version and license
info is displayed.</p>
<h2>Memory Layout</h2>
<p>There is 64K of RAM that the assembler will generate output into. Extra 64K
banks of RAM can be added by using the <b>bank</b> or <b>org</b> directives.
Banks are numbered from zero upwards.</p>
<h2>Source Code Layout</h2>
The source files follow this basic format:
<pre class="codeblock">
; Comments
;
label1: equ 0xffff
org $4000;
db "Hello, World\n",0
main jp local_label ; Comments
.local_label
inc a
another:
inc b
jp local_label ; Actually jumps to the following
; local_label.
.local_label
ret
</pre>
<p>The source files follow the following rules:</p>
<ul>
<li>Any text past a semicolon (;) is discarded as a comment (except when part
of a string constant).</li>
<li>Labels must start in column zero (the left hand most column).</li>
<ul>
<li>It is an error to redefine a global label that already exists.</li>
<li>If the label ends with a colon (:) then the colon is removed.</li>
<li>If the label doesn't start with a period (.) then it is assumed a global
label.</li>
<li>If the label starts with a period (.) then it is assumed to be a local
label. Local labels are associated with the preceding global label. If
a local label has the same name as a global variable the local value will be
used on expansion. If a local label already exists with the same name it
is an error.</li>
<li>Any label can be followed by an <code>equ</code> directive, in which case
the label is set to that value rather than the current program counter.</li>
<li>Labels are case-insensitive.</li>
</ul>
<li>Directives and opcodes must appear further along the line (anywhere else
other than the left hand column where labels live basically).</li>
<li>Strings can either be quoted with single or double quotes; this allows you
to put the other quote type inside the string.</li>
</ul>
<h2>Recognised directives</h2>
<p>The following directives are also recognised with an optional period (.) in
front of them, and are case insensitive. Directives can also be used to
control the output of a program listing, and the output of the assembly
itself. These are documented in subsequent sections.</p>
<table>
<thead><tr><td class="head">Directive</td>
<td class="head">Description</td></tr></thead>
<tr>
<td class="cmd">
processor <i>cpu</i>
</td>
<td class="def">
Sets the processor type to <i>CPU</i>. If omitted then Z80 is the default.
Note that this can appear multiple times in the same file. See the later
sections on processors to see what values are supported.</p>
</td></tr>
<tr><td class="cmd">
option <i>setting</i>, <i>value</i>
</td>
<td class="def">
Set options. Options are defined later on, and each CPU and output driver
can also have its own options. For options that support booleans
(on/off/true/false),the <i>setting</i> can be prefixed with a plus or minus
character to switch it on or off respectively.
</td></tr>
<tr><td class="cmd">
equ <i>value</i></code>
</td>
<td class="def">
Sets the top level label to <i>value</i>. Note this requires a label on the
same line as this directive.
</td></tr>
<tr><td class="cmd">
org <i>value</i>[, <i>bank</i>]
</td>
<td class="def">
Sets the program counter (PC) to <i>value</i>. The PC defaults to zero on
initialisation. If the optional second argument is passed the current memory
bank in use is set to <i>bank</i>. Note that it also possible to set the
bank by passing a 24-bit address. This was added for convenience when using the
65c816 processor.
</td></tr>
<tr><td class="cmd">
bank <i>value</i>
</td>
<td class="def">
The current memory bank in use is set to <i>value</i>.
</td></tr>
<tr><td class="cmd">
ds <i>value</i>[, <i>fill</i>]
</td>
<td class="def">
Skips the program counter on <i>value</i> bytes. If the optional <i>fill</i> is
provided then the bytes are filled with <i>fill</i>, otherwise they are filled
with zero.
</td>
<tr><td class="cmd">
db <i>value</i>[, <i>value</i>]
</td>
<td class="def">
Writes bytes represented by <i>value</i> to the current PC. The values can be
constants, expressions, labels or strings which are expanded to a list of byte
values for each character in the string.
</td></tr>
<tr><td class="cmd">
dw <i>value</i>[, <i>value</i>]
</td>
<td class="def">
Writes words (16-bit values) represented by <i>value</i> to the current PC.
The values can be constants, expressions, labels or strings. Strings are
written as 16-bit versions of their byte values, i.e. the high byte will be zero
and the low byte the character code.
</td></tr>
<tr><td class="cmd">
align <i>value</i>[, <i>fill</i>]
</td>
<td class="def">
Align the PC so that (PC modulus <i>value</i>) is zero. Will error if
<i>value</i> is less than 2 or greater that 32768. No values are written to
the skipped bytes unless the optional <i>fill</i> is supplied.
</td></tr>
<tr><td class="cmd">
import <i>filename</i>[, labels|all[, offset]]</code>
</td>
<td class="def">
Includes a simple library file as generated by casm. See the <a href="#libout">section on simple library files</a> for more details. If the optional second
argument is set to labels then only the label values are imported, otherwise
both memory and labels are imported. If the optional <i>offset</i> is given
then that offset is added onto the load address and defined labels.
</td></tr>
<tr><td class="cmd">
include <i>filename</i></code>
</td>
<td class="def">
Includes the source file <i>filename</i> as if it was text entered at the
current location.
</td></tr>
<tr><td class="cmd">
incbin <i>filename</i>
</td>
<td class="def">
Includes the binary file <i>filename</i> at the current PC, as if it was a
sequence of <code>db</code> directives with all the bytes from the file.
</td></tr>
<tr><td class="cmd">
alias <i>command</i>, <i>replacement</i>
</td>
<td class="def">
Creates an alias so that whenever the command <i>command</i> is found in the
source it is replaced with <i>replacement</i>. The idea of this is to make it
easier to import sources that use unknown directives, e.g.
<pre class="codeblock">
alias setaddr,org
alias ldreg,ld
cpu z80
setaddr $8000 ; These two are
org $8000 ; equivalent.
ld a,(hl) ; These two are
ldreg a,(hl) ; equivalent.
</pre>
</td></tr>
<tr><td class="cmd">
nullcmd
</td>
<td class="def">
Simply does nothing. It's only real use is as an alias if you wished to
strip a directive from a foreign source file.
</td></tr>
<tr><td class="cmd">
end
</td>
<td class="def">
Terminates input processing. Anything past the directive will be ignored.
</td></tr>
</table>
<h3>Built-in Aliases</h3>
The following are built-in aliases for the above directives.
<table>
<thead><tr><td class="head">Command</td>
<td class="head">Built-in Alias</td></tr></thead>
<tr><td class="cmd">processor</td>
<td class="alias">
proc<br>
arch<br>
cpu<br>
</td></tr>
<tr><td class="cmd">equ</td>
<td class="alias">
eq
</td></tr>
<tr><td class="cmd">ds</td>
<td class="alias">
defs
</td></tr>
<tr><td class="cmd">db</td>
<td class="alias">
defb<br>
byte<br>
text<br>
</td></tr>
<tr><td class="cmd">dw</td>
<td class="alias">
defw<br>
word<br>
</td></tr>
</table>
<h2>Options</h2>
<p>The core of CASM supports the following options that can be set via the
<b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option address24, <on|off>
</td>
<td class="def">
Controls whether addresses have the current bank set in the high word, e.g.
<pre class="codeblock">
org $8000
bank 7
option +address24
label1: ; Label1 == $078000
option -address24
label2: ; Label2 == $8000
</pre>
Note that the name is rather misleading; bank numbers are allowed to be greater
than 256.
</td></tr>
</table>
<h2>Expressions</h2>
<p>In any of the directives above, where a value is defined, an expression can
be entered.</p>
<p>Assembly instructions will also permit these expressions to be used where
applicable. As many opcodes use parenthesis to indicate addressing modes,
remember that {} brackets can be used to alter expression precedence.</p>
<pre class="codeblock">
ld a,{8+2}*2 ; On the Z80 loads A with the value 20
ld a,({8+2}*2) ; On the Z80 loads A with the value stored at
; address 20
</pre>
<p>Note that the expression is evaluated using a standard C int, and then cast
to the appropriate size.</p>
<p>The following formats for constant numbers are supported:</p>
<table>
<thead><tr><td class="head">Format (regular expression)</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
"." <i>or</i> '.'
</td>
<td class="def">
A single quoted character will be converted into the appropriate character
code.
</td></tr>
<tr><td class="cmd">
[1-9][0-9]*
</td>
<td class="def">
A decimal number, e.g. 42.
</td></tr>
<tr><td class="cmd">
0[0-7]*
</td>
<td class="def">
An octal number, e.g. 052.
</td></tr>
<tr><td class="cmd">
0x[0-9a-fA-f]+
</td>
<td class="def">
A hex number, e.g. 0x2a.
</td></tr>
<tr><td class="cmd">
[0-9a-fA-f]+h
</td>
<td class="def">
A hex number, e.g. 2ah.
</td></tr>
<tr><td class="cmd">
$[0-9a-fA-f]+
</td>
<td class="def">
A hex number, e.g. $2a.
</td></tr>
<tr><td class="cmd">
[01]+b
</td>
<td class="def">
A binary number, e.g. 00101010b
</td></tr>
<tr><td class="cmd">
%[01]+
</td>
<td class="def">
A binary number, e.g. %00101010
</td></tr>
<tr><td class="cmd">
[a-zA-Z_0-9]+
</td>
<td class="def">
A label, e.g. `main_loop`.
</td></tr>
</table>
The following operators are understood. The order here is the order of
precedence.
<table>
<thead><tr><td class="head">Arithmetic Operators</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
{ }
</td>
<td class="def">
Brackets used to alter the order of precedence. Note normal parenthesis
aren't used as the assembly language may make use of them.
</td></tr>
<tr><td class="cmd">
~ + -
</td>
<td class="def">
Bitwise NOT/unary plus/unary minus.
</td></tr>
<tr><td class="cmd">
<< >>
</td>
<td class="def">
Shift left/shift right.
</td></tr>
<tr><td class="cmd">
/ *
</td>
<td class="def">
Division/multiplication
</td></tr>
<tr><td class="cmd">
+ -
</td>
<td class="def">
Addition/subtraction.
</td></tr>
</table>
All the following have the same precedence, and so will be done left to right.
<table>
<thead><tr><td class="head">Comparison Operators</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
==
</td>
<td class="def">
Equality. Returns 1 if the arguments are equal, otherwise zero.
</td></tr>
<tr><td class="cmd">
!=
</td>
<td class="def">
Inequality. Returns 1 if the arguments are unequal, otherwise zero.
</td></tr>
<tr><td class="cmd">
< <= > >=
</td>
<td class="def">
Less than/less than or equal/greater than/greater than or equal. Returns 1
if the expression is true, otherwise zero.
</td></tr>
</table>
All the following have the same precedence, and so will be done left to right.
<table>
<thead><tr><td class="head">Boolean Operators</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
&& &
</td>
<td class="def">
Boolean/bitwise AND. For boolean operation arguments, zero is FALSE,
otherwise TRUE.
</td></tr>
<tr><td class="cmd">
|| |
</td>
<td class="def">
Boolean/bitwise OR.
</td></tr>
<tr><td class="cmd">
^
</td>
<td class="def">
Bitwise XOR.
</td></tr>
</table>
<h2>Character Sets</h2>
<p>The assembler has built-in support for a few different character sets.
These can be set by using the options `charset` or `codepage`, i.e.</p>
<pre class="codeblock">
option codepage, <i>format</i>
option charset, <i>format</i>
</pre>
<p>The following values can be used for <i>format</i>.</p>
<table>
<thead><tr><td class="head">Format</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
ascii
</td>
<td class="def">
7-bit ASCII. This is the default.
</td></tr>
<tr><td class="cmd">
spectrum
</td>
<td class="def">
The character codes as used on the Sinclair ZX Spectrum.
</td></tr>
<tr><td class="cmd">
cbm
</td>
<td class="def">
PETSCII as used on the Commodore Business Machine's range from the
PET to the C128. See <a href="https://en.wikipedia.org/wiki/PETSCII">
https://en.wikipedia.org/wiki/PETSCII</a> more details.
</td></tr>
<tr><td class="cmd">
c64
</td>
<td class="def">
The screen codes as used on the Commodore 64. Note these codes are different
to PETSCII and are the values to be poked into screen memory. The lower case
characters are the low part of the code -- these will appear onscreen either
in upper or lower case depending on the shift mode. The upper case characters
are either graphics characters or capital letters depending on the shift mode.
</td></tr>
<tr><td class="cmd">
zx81
</td>
<td class="def">
The character codes as used on the Sinclair ZX81. Lower case
letters are encoded as normal upper case letters and upper case
letter will be encoded as inverse upper case letters. In addition the following
characters that have no corresponding ZX81 character are mapped as:
<table>
<tr><td class="cmd">
#
</td>
<td class="def">
The British Pound sign.
</td></tr>
<tr><td class="cmd">
'
</td>
<td class="def">
Inverse double quotes.
</td></tr>
<tr><td class="cmd">
\
</td>
<td class="def">
Inverse slash.
</td></tr>
<tr><td class="cmd">
!
</td>
<td class="def">
Inverse question mark.
</td></tr>
<tr><td class="cmd">
|
</td>
<td class="def">
Inverse space.
</td></tr>
<tr><td class="cmd">
~
</td>
<td class="def">
Inverse minus sign.
</td></tr>
<tr><td class="cmd">
{ }
</td>
<td class="def">
Inverse round brackets.
</td></tr>
<tr><td class="cmd">
`
</td>
<td class="def">
The newline character. Note that the newline is actually a HALT opcode used to
terminate the line.
</td></tr>
</table>
</td></tr>
</table>
<p>e.g.</p>
<pre class="codeblock">
option +list
option +list-hex
option charset,ascii
db "Hello",'A'
; $48 $65 $6C $6C $6F $41
option charset,zx81
db "Hello",'A'
; $AD $2A $31 $31 $34 $A6
option codepage,cbm
db "Hello",'A'
; $48 $45 $4C $4C $4F $41
option codepage,spectrum
db "Hello",'A'
; $48 $65 $6C $6C $6F $41
</pre>
<h2>Macros</h2>
<p>
Macros can be defined in one of two ways; either parameterless or with named
parameters. Macro names are case-insensitive. In the parameterless mode the
special identifier '*' can be used to expand all arguments, which will be
separated with commas.
</p>
<p>
When expanded the macro will have an internally generated top-level label
assigned to it, so local variables will work inside the macro.
</p>
<p>e.g.</p>
<pre class="codeblock">
macro1: macro
ld a,\1
ld b,\2
ld hl,data
call \3
jr dataend
.data
defb \*
.dataend
endm
macro2: macro char,junk,interface
ld a,@char
ld b,@junk
call @interface
endm
</pre>
<p>
Note that trying to expand and unknown/missing argument will be replaced with
an empty string. Also the two argument reference styles can be mixed, though
obviously the @ form only makes sense in a parameterised macro, e.g.
</p>
<pre class="codeblock">
mac: macro char,junk,interface
ld a,@char
ld b,\2
call @interface
endm
</pre>
<p>
The at symbol (@) used for parameter expansion in named argument macros can
be replaced by using the following option, e.g.
</p>
<pre class="codeblock">
option macro-arg-char,&
</pre>
<p>
Note that this is enforced when the macro is <u>used</u> not when it is
defined.
Also the character must not be quoted, as that will be parsed as a string
holding the character code of the character.
</p>
<h2>Output Format</h2>
By default the assembled code is written to a file called <b>output</b> as raw
binary. The generated output can be controlled with the following options.
<table>
<thead><tr><td class="head">Output Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option output-file, <i>file</i>
</td>
<td class="def">
Send the output to <i>file</i>. Defaults to <b>output</b>.
</td></tr>
<tr><td class="cmd">
option output-bank, <i>printf formatted filename</i>
</td>
<td class="def">
Send the output if multiple banks to use to <i>printf formatted filename</i>.
It defaults to <b>output.%u</b> and accepts just one argument in the
formatting string of an unsigned integer.
If more or a different format specifier is used the behaviour of the assembler
will be undefined. How this is used depends on the output driver.
</td></tr>
<tr><td class="cmd">
option output-type, <i>format</i>
</td>
<td class="def">
Controls the format of the output file. The following are the
supported output formats:
<table>
<tr><td class="cmd">
<a href="#rawout">raw</a>
</td>
<td class="def">
A raw binary image.
</td></tr>
<tr><td class="cmd">
<a href="#specout">spectrum</a>
</td>
<td class="def">
A Spectrum emulator TAP file.
</td></tr>
<tr><td class="cmd">
<a href="#zx81out">zx81</a>
</td>
<td class="def">
A ZX81 emulator P file.
</td></tr>
<tr><td class="cmd">
<a href="#t64out">t64</a>
</td>
<td class="def">
A Commodore 64 T64 tape file.
</td></tr>
<tr><td class="cmd">
<a href="#gameboyout">gameboy</a>
</td>
<td class="def">
A Nintendo Gameboy ROM file.
</td></tr>
<tr><td class="cmd">
<a href="#snesout">snes</a>
</td>
<td class="def">
A SNES ROM file.
</td></tr>
<tr><td class="cmd">
<a href="#libout">lib</a>
</td>
<td class="def">
A simple library format that allows the importing of pre-built memory and
labels.
</td></tr>
<tr><td class="cmd">
<a href="#nesout">nes</a>
</td>
<td class="def">
A NES ROM file.
</td></tr>
<tr><td class="cmd">
<a href="#cpcout">cpc</a>
</td>
<td class="def">
An Amstrad CPC CDT file.
</td></tr>
<tr><td class="cmd">
<a href="#prgout">prg</a>
</td>
<td class="def">
A Commodore 64 or VIC-20 PRG file.
</td></tr>
<tr><td class="cmd">
<a href="#hexout">hex</a>
</td>
<td class="def">
An Intel HEX format file.
</td></tr>
</table>
</td></tr>
</table>
The output formats are described in detail in the following sections.
<h3 id="rawout">RAW Output Format</h3>
In this mode the file is created covering the block of memory that the assembly
touched. If memory banks have been used then the <b>output-bank</b> setting is
used to generate the output filename.
<h3 id="specout">Spectrum TAP Output Format</h3>
<p>
Generates a Spectrum TAP file for an emulator. A TAP file is a simple binary
file holding the bytes that the real Spectrum would have written to a tape.
</p>
<p>The TAP file will be given the same name as the output filename, and the
internal code block will also be given the same name, unless memory banks
have been used, in which case each code file in the TAP file will use the
<b>output-bank</b> setting to generate the filename for each block.
</p>
<p>If the options are set the TAP file will contain a BASIC loader for the
machine code.</p>
<p>
Remember that TAP files can be concatenated, so the output could be appended to
another TAP file.
</p>
<h4>Spectrum TAP Output Format options</h4>
<p>The Spectrum TAP output driver supports the following settings that can be
set via an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option spectrum-loader, <on|off>
</td>
<td class="def">
Whether the TAP file should contain a BASIC loader to load and run the machine
code.
</td></tr>
<tr><td class="cmd">
option spectrum-start, <i>address</i>
</td>
<td class="def">
The start address for the generated BASIC loader. If left undefined defaults
to the start of written memory.
</td></tr>
</table>
<h3 id="zx81out">ZX81 .P Output Format</h3>
<p>
Generates a P-file for an emulator. A ZX81 .P file is simply a dump of memory
from the system variables onwards.
</p>
<p>This format does not support memory blocks (the .P file is not a container
format) and so will only output anything in the first bank used, and using the
<b>output-file</b> for the filename.
</p>
<p>The output file will be created as a BASIC program, containing a REM
statement holding the machine code, and a command to execute the code. As
such the output will fail if the code in Bank 0 does not start at address 16514.
Your code must also support being executed from this address.
</p>
<p>Another important thing to note is about the display file. In the ZX81
memory map the DFILE can move around depending on the size of the program.
The output driver will create a display file for you. The easiest way to
reference this is to read the DFILE system variable when your program starts.
</p>
<p>Alternatively you can just as easily set up your own display file once
your program starts if you have special requirements, e.g. a display file for
pseudo hi-res.
</p>
<h4>ZX81 .P Output Format options</h4>
<p>The ZX81 output driver supports the following settings that can be set via
an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option zx81-margin, <pal|ntsc>
</td>
<td class="def">
Sets the MARGIN system variable appropriately either for the PAL or NTSC
TV system. Defaults to PAL.
</td></tr>
<tr><td class="cmd">
option zx81-autorun, <on|off>
</td>
<td class="def">
Whether the ZX81 should auto run the machine code. Defaults to on.
</td></tr>
<tr><td class="cmd">
option zx81-collapse-dfile, <on|off>
</td>
<td class="def">
Whether the display file should be generated collapsed (e.g. for 1K mode).
Defaults to off.
</td></tr>
</table>
<h3 id="t64out">C64 T64 Tape Output Format</h3>
<p>
Generates a T64 tape file for an emulator.
</p>
<p>The tape file will be given the same name as the output filename, and the
internal code block will also be given the same name, unless memory banks
have been used, in which case then each entry in the tape file will use the
<b>output-bank</b> setting to generate the filename for each entry.
</p>
<p>The first (or only) bank will have a small BASIC program inserted as part of
the generated file. For this reason the first bank should start near the BASIC
area (0x820 should be a safe place to start) unless you have a great
desire for a tape full of zero bytes. This BASIC will simply hold a SYS command
to start the machine code, e.g.
</p>
<pre class="codeblock">
10 SYS 2080
</pre>
<p>Any remaining blocks will be stored as-is without any basic loader.</p>
<h4>C64 T64 Tape Output Format options</h4>
<p>The C64 T64 output driver supports the following settings that can be
set via an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option t64-start, <i>address</i>
</td>
<td class="def">
The start address for the generated BASIC loader. If left undefined defaults
to the start of written memory in the first bank.
</td></tr>
</table>
<h3 id="gameboyout">Nintendo Gameboy ROM File Output Format</h3>
<p>
Generates a ROM file for a Gameboy emulator or hardware. Note that large ROM
sizes have not been extensively checked and verified.
</p>
<p>If a single bank was used during the assembly then a simple 32K ROM is
assumed, and an error will be shown if the addresses used fall outside the range
0x150 to 0x7fff. </p>
<p>Similarly if multiple banks are used then it is assumed that the first bank
is only used in the range 0x150 to 0x3fff, and subsequent banks in the range
0x4000 to 0x7fff. This is to fit in with the method the Gameboy uses to page
memory banks into the upper 16K portion of the normal 32K ROM address space.
</p>
<p>By default the output driver will try and fill in the ROM size and type in
the header properly, but these can be overridden using settings.</p>
<h4>Gameboy ROM Output Format options</h4>
<p>The Gameboy output driver supports the following settings that can be set via
an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option gameboy-colour, <on|off>
</td>
<td class="def">
Whether this is a Gameboy Colour cartridge. Defaults to <i>off</i>.
Note that <b>gameboy-color</b> can be used as a different spelling for this
setting.
</td></tr>
<tr><td class="cmd">
option gameboy-super, <on|off>
</td>
<td class="def">
Whether this is a Gameboy Super extended cartridge. Defaults to <i>off</i>.
</td></tr>
<tr><td class="cmd">
option gameboy-cart-type, <i>number</i>
</td>
<td class="def">
Specifies the cartridge type. Defaults to -1, which means the output driver
will try and pick the appropriate type.
</td></tr>
<tr><td class="cmd">
option gameboy-irq, <i>irq</i>, <i>address</i>
</td>
<td class="def">
Specifies an address where an IRQ routine is stored, and requests that the
IRQ be transferred to that address when it happens. The IRQ routine must end
with a <b>reti</b> opcode.<br><br>
<i>irq</i> can be either <b>vbl</b>, <b>lcd</b>, <b>timer</b>, <b>serial</b>
or <b>joypad</b>. If left at the default value of -1 then an IRQ handler is
installed with just a <b>reti</b> instruction.
</td></tr>
</table>
<h3 id="snesout">SNES ROM File Output Format</h3>
<p>
Generates a ROM file for a SNES emulator or hardware. Note that large ROM
sizes have not been extensively checked and verified.
</p>
<p>If a single bank was used during the assembly then a simple 32K ROM is
assumed, and an error will be shown if the addresses used fall outside the range
0x150 to 0x7fff. </p>
<p>Similarly if multiple banks are used then it is assumed that the first bank
is only used in the range 0x150 to 0x3fff, and subsequent banks in the range
0x4000 to 0x7fff. This is to fit in with the method the Gameboy uses to page
memory banks into the upper 16K portion of the normal 32K ROM address space.
</p>
<p>By default the output driver will try and fill in the ROM size and type in
the header properly, but these can be overridden using settings.</p>
<h4>SNES ROM Output Format options</h4>
<p>The SNES output driver supports the following settings that can be set via
an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option snes-name, <i>name</i>
</td>
<td class="def">
Sets the name of the cartridge. Defaults to "NONAME" if not set.
</td></tr>
<tr><td class="cmd">
option snes-rom-type, <lorom|hirom|lorom-fast|hirom-fast>
</td>
<td class="def">
Defines the memory mapping used for this cartridge. A detailed explanation
is beyond this document, but note that when lorom is used then just the upper
32K of each bank is used to generate the ROM. This is to make life easier,
as the real physical mapping would make the lower 32K of a ROM bank
mapped into the upper 32K address space. This way no hoops have to be jumped
through.
</td></tr>
<tr><td class="cmd">
option snes-irq, <i>irq</i>, <i>address</i>
</td>
<td class="def">
Specifies an address where an IRQ routine is stored, and sets the appropriate
vectors in emulation and native mode. <i>irq</i> can either by <b>vbl</b> for
the vertical blanking interrupt and <b>irq</b> which is used for the scan-line
interrupt. Note that an error is generated if a <b>vbl</b> routine is not
supplied.
</td></tr>
<tr><td class="cmd">
option snes-ram-size, <i>size</i>
</td>
<td class="def">
Sets the RAM size in the ROM header.
</td></tr>
<tr><td class="cmd">
option snes-rom-size, <i>size</i>
</td>
<td class="def">
Sets the ROM size in the ROM header, overriding the calculated value the output
driver would generate.
</td></tr>
</table>
<h3 id="libout">Simple Library Output Format</h3>
<p>This mode produces a simple library file that can be imported using the
<b>import</b> command. This is of use if you wish to split a large project
into smaller assembly jobs, for example, to stop you needing to assemble large
chunks of graphics data every time. The library contains all the memory from
the assembled file and records the values of all global labels. Note that
private macro variables and local labels aren't saved, but they'd be useless
anyway.</p>
<p>.e.g.</p>
<b>Makefile</b>
<pre class="codeblock">
game.sfc: game.lib gfx.lib
casm link.asm
game.lib: game.asm
casm game.asm
gfx.lib: gfx.asm
casm gfx.asm
</pre>
<b>link.asm</b>
<pre class="codeblock">
processor 65c816
option output-file,"game.sfc"
option output-format,snes
; These labels actually come from game.asm
;
option snes-irq,vbl,vbl_handler
option snes-irq,irq,irq_handler
import "game.lib"
import "gfx.lib"
</pre>
<b>game.asm</b>
<pre class="codeblock">
processor 65c816
org $8000
bank 0
;
; Lots of code....
;
</pre>
<b>gfx.asm</b>
<pre class="codeblock">
processor 65c816
org $8000
bank 1
;
; Lots of gfx data....
;
</pre>
<h3 id="nesout">NES ROM File Output Format</h3>
<p>
Generates a ROM file for a NES emulator or hardware. Note that large ROM
sizes have not been extensively checked and verified.
</p>
<p>It searches for banks with code in the range 0x8000 to 0xffff, or just in the
range 0xc000 to 0xffff if there is just one ROM code bank. Video ROM (VROM)
banks are identified by just using addresses up to 0x1fff.</p>
<p>The output driver will output the appropriate number of ROM and VROM chunks
to the file depending on these, and will error if there are no ROM banks
or banks using illegal addresses.</p>
<h4>NES ROM Output Format options</h4>
<p>The NES output driver supports the following settings that can be set via
an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option nes-vector, <i>vector</i>, <i>address</i>
</td>
<td class="def">
Specifies an address where an IRQ routine is stored, and sets the appropriate
vectors in the appropriate place in memory. <i>irq</i> can either by
<b>reset</b>, <b>nmi</b> or <b>brk</b>.<br><br>
<b>reset</b> is for the reset vector (i.e. where the ROM runs from). If
undefined a warning is displayed and the vector will automatically be set to
either 0x8000 or 0xc000 according to the ROM size.<br><br>
<b>nmi</b> is the NMI vector used for the vertical blanking interrupt. If
undefined a warning is issued.<br><br>
<b>brk</b> is the vector used for software interrupts from the brk command.
This can be left undefined if not needed.
</td></tr>
<tr><td class="cmd">
option nes-mapper, <i>number</i>
</td>
<td class="def">
Sets the mapper type in the output file header. If undefined left at zero,
which is the correct one if you have 16 or 32K of code ROM and 8KB of video
ROM.
</td></tr>
<tr><td class="cmd">
option nes-tv-format, pal|ntsc
</td>
<td class="def">
Defines the TV format stored in the ROM header, defaulting to <b>pal</b>.
</td></tr>
<tr><td class="cmd">
option nes-mirror, horizontal|vertical|vram
</td>
<td class="def">
Defines whether nametables are mirrored horizontally, vertically or not at
all respectively. Defaults to <b>horizontal</b>.
</td></tr>
<tr><td class="cmd">
option nes-battery-ram, on|off
</td>
<td class="def">
Defines whether there is battery backed RAM in the cartridge. Defaults to
<b>off</b>.
</td></tr>
</table>
<h3 id="cpcout">Amstrad CPC CDT Output Format</h3>
<p>
Generates an Amstrad CPC TAP file for an emulator.
The file can also be run into a real CPC using TZX to wav file converters.
</p>
<p>The CDT file will be given the same name as the output filename,
unless memory banks have been used, in which case each code file in the CDT
file will use the <b>output-bank</b> setting to generate the filename for
each block.
</p>
<h4>Amstrad CPC CDT Output Format options</h4>
<p>The Amstrad CPC CDT output driver supports the following settings that can be
set via an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option cpc-start, <i>address</i>
</td>
<td class="def">
The start address for the tape file. If left undefined defaults to the start
of written memory.
</td></tr>
<tr><td class="cmd">
option cpc-loader, <on|off>
</td>
<td class="def">
Whether the CDT file should contain a BASIC loader to load and run the machine
code.
</td></tr>
</table>
<h3 id="prgout">C64/VIC-20 PRG Output Format</h3>
<p>
Generates a PRG file for an emulator or real hardware.
</p>
<p>The tape file will be given the same name as the output filename, and the
internal code block will also be given the same name, unless memory banks
have been used, in which case then each entry in the tape file will use the
<b>output-bank</b> setting to generate the filename for each entry.
</p>
<p>All banks will have a small BASIC program inserted as part of
the generated file. For this reason the bank should start near the BASIC
area (0x820 should be a safe place to start for the C64) unless you have a great
desire for a PRG full of zero bytes. This BASIC will simply hold a SYS command
to start the machine code, e.g.
</p>
<pre class="codeblock">
10 SYS2080
</pre>
<h4>C64/VIC-20 PRG Output Format options</h4>
<p>The PRG output driver supports the following settings that can be
set via an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option prg-start, <i>address</i>
</td>
<td class="def">
The start address for the generated BASIC loader. If left undefined defaults
to the start of written memory in the bank.
</td></tr>
<tr><td class="cmd">
option prg-system, <c64|vic20|vic20+8k>
</td>
<td class="def">
The system to generate the PRG file for, either a Commodore 64 (<b>c64</b>),
VIC-20 either unexpanded or with 3K expansion (<b>vic20</b>) or a VIC-20 with
an 8K or 16K expansion (<b>vic20+8k</b>).
</td></tr>
</table>
<h3 id="hexout">Intel HEX Output Format</h3>
<p>
Generates a Intel HEX file for an emulator or real hardware. This format is
used by various tools and programmers.
</p>
<h4>Intel HEX Output Format options</h4>
<p>The Intel HEX output driver supports the following settings that can be
set via an <b>option</b> command.
</p>
<table>
<thead><tr><td class="head">Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option hex-null, <i>value</i>
</td>
<td class="def">
Sets the value that the output handler considers an empty byte that doesn't
need to be output. Defaults to zero.
</td></tr>
</table>
<h2>Listing</h2>
<p>
By default no output listing is generated. This can be controlled by the
following options.
</p>
<table>
<thead><tr><td class="head">Listing Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option list, <on|off>
</td>
<td class="def">
Enables or disables listing. The listing will go to stdout by default.
Defaults to <i>off</i>.
</td></tr>
<tr><td class="cmd">
option list-file, <i>filename</i>
</td>
<td class="def">
Sends the listing to <i>filename</i>. Note this should appear before enabling
the listing.
</td></tr>
<tr><td class="cmd">
option list-pc, <on|off>
</td>
<td class="def">
Control the output of the current PC in the as a comment preceding the
line (so that a listing could be reassembled with no editing). Defaults
to <i>off</i>.
</td></tr>
<tr><td class="cmd">
option list-hex, <on|off>
</td>
<td class="def">
Control the output of the bytes generated by the source line in hex.
Defaults to <i>off</i>. If <i>on</i> then the hex is output in a comment
preceding the line (possibly with the PC above), so that a listing is still
valid as input to the assembler.
</td></tr>
<tr><td class="cmd">
option list-labels, <on|off|all>
</td>
<td class="def">
Controls the listing of labels, either:
<table>
<tr><td class="cmd">
off
</td>
<td class="def">
The default; don't list anything.
</td></tr>
<tr><td class="cmd">
on
</td>
<td class="def">
List labels at the end of the listing. The labels are output commented so that
the list could be used as input.
</td></tr>
<tr><td class="cmd">
all
</td>
<td class="def">
List all labels, including internally generated private labels for macros.
</td></tr>
</table>
</td></tr>
<tr><td class="cmd">
option list-macros, <off|exec|dump|all>
</td>
<td class="def">
Controls the listing of macro invocations, either:
<table>
<tr><td class="cmd">
off
</td>
<td class="def">
The default; don't list anything.
</td></tr>
<tr><td class="cmd">
exec
</td>
<td class="def">
List invocations of macros.
</td></tr>
<tr><td class="cmd">
dump
</td>
<td class="def">
Produce a list of macro definitions at the end of the listing.
</td></tr>
<tr><td class="cmd">
all
</td>
<td class="def">
Combine <i>exec</i> and <i>dump</i>.
</td></tr>
</table>
</td></tr>
<tr><td class="cmd">
option list-rm-blanks, <on|off>
</td>
<td class="def">
Defaults to <i>on</i>. This option causes multiple blank lines to be collapsed
down to a single blank line in the listing.
</td></tr>
</table>
<h1 id="z80">Z80 CPU</h1>
<h2>Using the Z80</h2>
The Z80 processor can be selected by passing <b>z80</b> to the processor
directive, i.e.
<pre class="codeblock">
processor z80
</pre>
<h2>Opcodes</h2>
<p>
The Z80 assembler uses the standard Zilog opcodes, and supports
undocumented instructions.
</p>
<p>
For instructions were the Accumulator can be assumed it can be omitted, and
EOR can be used the same as XOR:
</p>
<pre class="codeblock">
xor a,a ; These are equivalent
xor a
eor a,a
and a,b ; These are equivalent
and b
</pre>
<p>
For exchange opcodes with parameters the parameters can be reversed from their
official form:
</p>
<pre class="codeblock">
; The official forms
;
ex de,hl
ex af,af'
ex (sp),hl
ex (sp),ix
ex (sp),iy
; Also supported
;
ex hl,de
ex af',af
ex hl,(sp)
ex ix,(sp)
ex iy,(sp)
</pre>
<p>
Where the high/low register parts of the IX and IY registers are to be used,
simply use ixl, iyl, ixh and iyh. Note that the assembler will accept
illegal pairings involving H and L, but these will be warned about:
</p>
<pre class="codeblock">
ld ixh,$e5
ld iyl,iyl
ld ixh,l ; This will be turned into "ld ixh,ixl" and a
; warning will be issued.
ld iyh,ixl ; This will generate an error as the index registers
; have been mixed.
</pre>
<p>
For the hidden bit manipulations that also can copied to a register, these can
be represented by adding the destination register as an extra parameter, e.g.
</p>
<pre class="codeblock">
srl (iy-1),d
set 3,(iy-1),a
res 4,(iy-1),b
</pre>
<p>
For the hidden IN instruction using the flag register the following are all
equivalent:
</p>
<pre class="codeblock">
in (c)
in f,(c)
</pre>
<p>
For the hidden OUT instruction using the flag register, $00 or $ff depending
on where you're reading, the following are all equivalent, where <i>value</i>
can be any value at all:
</p>
<pre class="codeblock">
out (c)
out (c),f
out (c),<i>value</i>
</pre>
<h2>Options</h2>
The Z80 assembler has no options.
<h1 id="6502">6502 CPU</h1>
<h2>Using the 6502</h2>
The 6502 processor can be selected by passing <b>6502</b> to the processor
directive, i.e.
<pre class="codeblock">
processor 6502
</pre>
<h2>Opcodes</h2>
The 6502 assembler uses the standard Motorola opcodes. Undocumented opcodes are
supported and use the opcodes as described at
<a href="https://www.masswerk.at/nowgobang/2021/6502-illegal-opcodes">
www.masswerk.at/nowgobang/2021/6502-illegal-opcodes</a>.
<h2>Options</h2>
The 6502 assembler has the following options.
<table>
<thead><tr><td class="head">6502 Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option zero-page, <on|off|auto>
</td>
<td class="def">
Controls the assumptions made regarding Zero Page address. Defaults to
<i>auto</i>, and can be the following values:
<table>
<tr><td class="cmd">
off
</td>
<td class="def">
All addresses are assumed to be not on the Zero Page, regardless
of the value used.
</td></tr>
<tr><td class="cmd">
on
</td>
<td class="def">
Assumes all addresses are in the Zero Page, raising an error if any address is
not in the Zero Page.
</td></tr>
<tr><td class="cmd">
auto
</td>
<td class="def">
Treats addresses less than 256 as being in the Zero Page automatically. This
mode also makes the assembler perform an extra pass to guard against the
possibility of the calculation being fooled.
</td></tr>
</table>
e.g.
<pre class="codeblock">
cpu 6502
org $8000
lda $0000,x ; Produces $bd $00 $00
option +zero-page
lda $0000,x ; Produces $b5 $00
lda $1234,x ; Produces an error
option zero-page,auto
lda $00,x ; Produces $b5 $00
lda $8000,x ; Produces $bd $00 $80
</pre>
</td></tr>
</table>
<h1 id="gbcpu">Gameboy Z80 derivative CPU</h1>
<h2>Using the Gameboy Z80 derivative</h2>
The Gameboy Z80 derivative processor can be selected by passing <b>gameboy</b>
to the processor directive, i.e.
<pre class="codeblock">
processor gameboy
</pre>
<h2>Opcodes</h2>
<p>
The Gameboy assembler uses the standard Z80 opcodes where applicable.
Note that the Gameboy processor has a reduced number of opcodes, flags
and no index registers, though it has some additional instructions and
addressing modes.
</p>
<p>
For instructions were the Accumulator can be assumed it can be omitted, and
EOR can be used the same as XOR:
</p>
<pre class="codeblock">
xor a,a ; These are equivalent
xor a
eor a,a
and a,b ; These are equivalent
and b
</pre>
<p>
The Gameboy CPU has a special addressing mode used for one opcode, where the
referenced address is stored as a single byte, and used as an offset into the
top page (0xff00). This can be either triggered by using the special opcode, or
will automatically used whenever an address is accessed in the range 0xff00 to
0xffff:
</p>
<pre class="codeblock">
; These all will use the special addressing mode opcode, accessing
; memory location $ff34
;
label equ $ff34
ldh a,($34)
ldh a,($ff34)
ld a,($ff34)
ld a,(label)
ld (label),a
ld ($ff34),a
ldh ($34),a
ldh ($ff34),a
</pre>
<p>
The Gameboy CPU also supports incrementing or decrementing the HL register when
it is used as an address:
</p>
<pre class="codeblock">
; All these decrement HL after the value has been used.
;
ld a,(hl-)
ld a,(hld)
ldd a,(hl)
ld (hl-),a
ld (hld),a
ldd (hl),a
; All these increment HL after the value has been used.
;
ld a,(hl+)
ld a,(hli)
ldi a,(hl)
ld (hl+),a
ld (hli),a
ldi (hl),a
</pre>
<p>In addition the Gameboy CPU supports these extra instructions over the Z80:
</p>
<pre class="codeblock">
; Actually loads using the address $ff00 + C
;
ld a,(c)
ld (c),a
; Put the Gameboy into a low-power mode till a control is pressed.
; Note it is accepted practice to put a NOP afterwards. This may be
; due to the stop replacing DJNZ, which may still be wired to expect
; an argument. That is just a wild guess though.
;
stop
nop
; Swaps the low/high nibbles of the register
;
swap a
swap b
swap c
swap d
swap e
swap h
swap l
swap (hl)
</pre>
<h2>Options</h2>
The Gameboy CPU assembler has no options.
<h1 id="65c816">65c816 CPU</h1>
<h2>Using the 65c816 processor</h2>
The 65c816 processor can be selected by passing <b>65c816</b>
to the processor directive, i.e.
<pre class="codeblock">
processor 65c816
</pre>
<h2>Opcodes</h2>
The 65c816 assembler uses the standard opcodes. As an addition some implicit
opcodes are generally followed by a byte that can be used, e.g. in the case
of a BRK interrupt. In these cases the following byte is automatically set to
zero unless a argument is supplied (in any addressing mode) and this is written
out as the following byte. e.g.
<pre class="codeblock">
processor 65c618
brk ; Produces the bytes 0x00 0x00
brk $ff ; Produces the bytes 0x00 0xff
wdm ; Produces the bytes 0x42 0x00
wdm $80 ; Produces the bytes 0x42 0x80
</pre>
<h2>Additional Directives</h2>
The 65c618 assembler has some addition directives. As with the built-in
directives, these can be preceded by an optional period (.) character.
<table>
<thead><tr><td class="head">Directive</td>
<td class="head">Description</td></tr></thead>
<tr>
<td class="cmd">
m8
</td>
<td class="def">
Sets the assembler to produce 8-bit immediate values for the Accumulator in the
appropriate instructions.
</td></tr>
<td class="cmd">
m16
</td>
<td class="def">
Sets the assembler to produce 16-bit immediate values for the Accumulator in the
appropriate instructions.
</td></tr>
<td class="cmd">
x8
</td>
<td class="def">
Sets the assembler to produce 8-bit immediate values for the index registers X
and Y in the appropriate instructions.
</td></tr>
<td class="cmd">
x16
</td>
<td class="def">
Sets the assembler to produce 16-bit immediate values for the index registers X
and Y in the appropriate instructions.
</td></tr>
<tr><td class="cmd">
mx <i>accumulator-size</i>, <i>index-size</i>
</td>
<td class="def">
Sets the Accumulator and index register sizes for immediate values to either
8 or 16 bits.
</td></tr>
</table>
<h2>Options</h2>
The 65c618 assembler has the following options.
<table>
<thead><tr><td class="head">65c618 Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option a16, <on|off>
</td>
<td class="def">
Switches on or off the generation of 16-bit absolute values for the Accumulator.
Note that this can also be done using the directives described in the previous
section.
</td></tr>
<tr><td class="cmd">
option i16, <on|off>
</td>
<td class="def">
Switches on or off the generation of 16-bit absolute values for the index
registers X and Y.
Note that this can also be done using the directives described in the previous
section.
</td></tr>
</table>
<h1 id="spc700">SPC700 CPU</h1>
<h2>Using the SPC700</h2>
The SPC700 processor can be selected by passing <b>spc700</b> to the processor
directive, i.e.
<pre class="codeblock">
processor spc700
</pre>
<h2>Opcodes</h2>
I could find no official documentation on The SPC700, so the assembler uses what
seems to be the accepted opcode format.
<h2>Options</h2>
The SPC700 assembler has the following options.
<table>
<thead><tr><td class="head">SPC700 Option</td>
<td class="head">Description</td></tr></thead>
<tr><td class="cmd">
option direct-page, <on|off|auto>
</td>
<td class="def">
Controls the assumptions made regarding Direct Page address. Defaults to
<i>auto</i>, and can be the following values:
<table>
<tr><td class="cmd">
off
</td>
<td class="def">
All addresses are assumed to be not on the Direct Page, regardless of the value
used.
</td></tr>
<tr><td class="cmd">
on
</td>
<td class="def">
Assumes all addresses are in the Direct Page, raising an error if any address is
not in the Direct Page.
</td></tr>
<tr><td class="cmd">
auto
</td>
<td class="def">
Treats addresses less than 256 as being in the Direct Page automatically. This
mode also makes the assembler perform an extra pass to guard against the
possibility of the calculation being fooled.
</td></tr>
</table>
</td></tr>
</table>
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