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Assembler for Microchip PIC16Cxx microcontrollers
Version 1.14
Copyright 1995-2005 by Timo Rossi. All rights reserved. See the file
"[1]LICENSE" for information about redistribution conditions.
Timo Rossi
email: [2]trossi@iki.fi
www: [3]http://www.iki.fi/trossi/pic/
NOTE: This document file has not been properly updated. There is
support for many new PICs (including 16-bit ones), and some new
directives.
The code is (mostly) ISO-C90, and should compile with most platforms
(It does assume that negative integers are stored in two's complement
representation) And it uses the strcasecmp() or stricmp() function).
The code also uses the so-called "struct hack". Also, the snprintf()
function (standard in ISO-C99) is used.
Command line usage:
picasm [-o<objname>] [-l<listfile>] [-ihx8m] [-ihx16] [-pic<device>]
<filename>
Options:
-o<filename> Define output file name. Default is
<source_without_ext>.hex.
-l[<listfile>] Enable listing. Default listing file name is
<source_without_ext>.lst.
-s Includes symbol table in listing. Does nothing if listing is not
enabled.
-w[<warnlevel>] Give more warnings. If <warnlevel> is omitted, one is
assumed. Level two warns also about tris/option instructions on 14-bit
PICs.
-i<include_dir> Add a directory to the include file search path.
Several -i -options can be used to add multiple directories.
-d<symbol> [ = <value> ] Define an assembler symbol. The value of the
symbol must be a decimal or hex number (hex uses 0x-prefix). If a
value is not given, the symbol value becomes 1. Multiple -d- options
can be used to define multiple symbols.
-ihx8m IHX8M output format (default).
-ihx16 IHX16 output format.
-pic<device> Select PIC device. The PIC types are defined in special
include files (see the device_definitions directory).
Code syntax
The basic syntax that this assembler uses is similar to the syntax of
the Microchip assembler. However, many directives and expressions are
different.
Assembler mnemonics and directives must not be located in the very
beginning of a line (tabs or spaces should be used, unless the line
begins with a label). Labels must either end with a colon, or start at
the beginning of a line.
This is a single-pass assembler, forward gotos/calls are patched at
the end of the assembly (only single labels are accepted in that case,
otherwise expressions can be used too)
In current versions forward references can also be used with movlw,
addlw and retlw (only the low 8 bits of an address are used.)
Expressions
Expressions can have the following elements: (from highest precedence
to the lowest).
integer constants
symbols
(<expression>)
. (or $) current location
defined(<symbol>) TRUE (-1) if symbol is defined else FALSE (0).
streq("str1", "str2") TRUE if strings are identical.
streqcase("str1", "str2") The same as streq() but ignores case (Only
for ASCII characters, not ISO-Latin, Unicode etc.).
isstr(<arg>) TRUE is argument is a quoted string.
chrval("str", <pos>) Returns ASCII character code from the string.
Position range is from 0 to string length-1. If position is out of
range, returns -1.
hibyte(label) Return the high byte of the label address. Useful for
accessing program memory using the eeadr/eeadrh registers. Forward
reference is allowed when hibyte() is not used as a part of a more
complex expression.
[ expr1 expr2... expr_n ] The same as (1 << expr1) | (1 << expr2) ...
(builds a number by setting individual bits)
- unary minus
~ bitwise not
* multiply
/ divide
% modulo/remainder
& bitwise and
+ add
- subtract
| bitwise or
^ bitwise exclusive or
<< shift left
>> shift right
== equal
!=, <> not equal
< less than
<=, =< less or equal than
> greater than
>=, => greater or equal than
The compare operators return TRUE (-1) or FALSE (0) (they are useful
with conditional assembly).
Expressions are evaluated as 32-bit integers (or whatever size 'long'
is).
hex numbers 0x<digits>, h'<digits>', $<digits> or <digits>h (must
begin with 0..9)
octal numbers <digits>o, o'<digits>'
binary numbers 0b<digits>, b'<digits>' or <digits>b
decimal numbers without prefix or d'<digits>'.
Directives
(square brackets denote optional parameters)
<label> equ <expr> Define a constant
<label> set <expr> Define a variable (similar to equ but can be
redefined with another set-directive)
org <address>
org <address>, <mode>
org <mode> Specify origin for program code, register file or data
EEPROM. <mode> is "code" for program code, "reg" for register file and
"edata" for data EEPROM. If mode is not given, it is determined
automatically from first instruction that generates output to the hex
file. After that the mode cannot be changed without another ORG
statement. When ORG is used with only the mode parameter, the address
continues from the last value for that mode.
include " <filename>" Include another source file. Includes can be
nested. #include is an alternate name for this
end End assembly. anything after this is ignored.
<label> ds <expr> Reserve <expr> number of file register (RAM)
locations. ORG must be set for this to work.
<label> edata <expr> [, <expr>... ] Define data EEPROM contents (only
with PICs with data EEPROM)
dt <value1> [ , <value2>... ] Generate an array retlw instructions
with the specified return values (typically used for table lookup in
PIC assembler code. You can also use a list of multiple return values
with the actual retlw -mnemonic to generate to a list of retlw
instructions.)
if <expr>
<code1>
[ else
<code2> ]
endif Conditional assembly. If <expr> is non-zero, <code1> after
the if-directive is assembled, and the optional <code2> is skipped. If
<expr> is zero, <code1> is skipped and optional <code2> is assembled.
<macroname> macro
<macro definition>
endm
Define a macro.
Macro parameters are \1...\9, \# is the number of parameters. \@ (or
\0) is an number that is different for each macro expansion (it can be
used to generate unique labels inside macros). Macros can be
recursive.
exitm Exit macro (can only be used inside a macro definition.
Useful with conditional assembly)
local
endlocal
Begin and end a local label/symbol block.
Local symbols must be prefixed with "=" and their name scope is only
the current local symbol block. Local symbol blocks can be nested but
only the symbols in the currently active block can be used (the
symbols in the inner and outer blocks are not visible)
config <config_param> [, <config_param>...] Define PIC
configuration fuse data. <config_param> can be:
CP=<on_off> Code protection (default off, partial protection not
supported)
PWRTE=<on_off> Powerup timer (default varies with PIC models, not
valid with 12-bit PICs). Also PWRT=<on_off>.
WDTE=<on_off> Watchdog (default on). Also WDT=<on_off>.
BODEN=<on_off> Brown-out detect. only valid with some PIC models. Also
BOD=<on_off>.
OSC=<osctype> Oscillator type (typically HS, XT, LP, RC, some PIC
models have different options)
The <on_off> parameter can be:
on, yes, enabled on
off, no, disabled off
The fuses are located in address 0xfff with 12-bit PICs and 0x2007
with 14-bit PICs.
picid <id1>, <id2>, <id3>, <id4>
Define PIC ID values.
The ID is located in the hex file at the address following program
memory end with 12-bit PICs, and at 0x2000 with 14-bit PICs.
device <device> Select PIC device type. The PIC types are defined
in special include files. (see the device_definitions directory).
opt <option> Set assembly options. Currently only implemented:
list or l turn listing on
nolist or nol turn listing off
error <error_message> Causes an assembly error.
References
1. file://localhost/home/trossi/work/pic/picasm114/LICENSE
2. mailto:trossi@iki.fi
3. http://www.iki.fi/trossi/pic/
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