ASM 6502 Assembler made in Python
WARNING: This project is currently in alpha stage. Some features may be incomplete, have bugs, or change.
Usage: py sdasm.py [-h] [-l ] [-bin ] [-cfg ] [-fulltb] [-d ] [-q] [-symbols ] sourcefile [outputfile]
- Supports all (official) 6502 opcodes
- Anonymous labels, local labels
- macros, functions
Configuration: After running once, a config.ini will be generated. Some syntax may be changed with configuration.
Opcodes: Standard 6502 ocodes are supported.
Comments: Comments start with ";" or "//", and can also be used at the end of a line. Block-level comments are enclosed in "/" "/".
; This is a comment
// This is also a comment
/*
This is a block level comment
*/
Line Continuation: A \ at the end of a line may be used as a line continuation. Whitespace after the character will be ignored.
A , may also be used, but will preserve the , character.
Labels may end in a colon. Code can be placed on the same line as labels.
Anonymous labels are 1 or more "-" or "+" characters. These labels will only
search backwards for "-" and forwards for "+". Named directional labels can
also be made by prefixing with "-" or "+". Labels starting with '@' are
local labels. They have limited scope, visible only between non-local labels.
Start:
- lda PPUSTATUS ; wait one frame
bpl -
- lda PPUSTATUS ; wait another frame
bpl -
ldx #$05
-loopstart
dex
bne -loopstart
label1:
@tmp1:
@tmp2:
label2:
@tmp1:
@tmp2:
Hexadecimal numbers start with "$". Binary numbers start with "%".
A "$" by itself may be used to get or set the current address.
lda #$00 ; The "#" indicates an "immediate" value.
ora #%00001100
sta $4002
Symbols and expressions enclosed in {} can be used to insert them
anywhere, even in text.
file = foobar
include "{file}.asm"
Lists can be used in most places. List indexes start with 0.
list = [1,2,3] ; Create a list
list = 1,2,3 ; Create a list
list[2] ; Set the value of a list item.
list = {concat:list, 5} ; Add an item to the end of list
There are a number of special "filters" using the format {filter: data}
shuffle
Shuffle a list of bytes.
db {shuffle:$00, $01, $02, $03, $04} ; outputs 5 bytes in random order
a = 1,2,3,4,5 ; Create list
a = {shuffle:a} ; Shuffle list
choose
Choose a random item from a list.
db {choose:$01, $02, $03} ; outputs either $01, $02 or $03
random
Generate a random number.
db {random:256} ; outputs a random number from 0 to 255.
db {random:5,10} ; outputs a random number from 5 to 9.
range
Generate a range of numbers.
db {range:3} ; outputs 0,1,2,3
db {range:5,10} ; outputs 5,6,7,8,9,10
db {range:0,10,2} ; outputs 0,2,4,6,8,10
db {range:5,0,-1} ; outputs 5,4,3,2,1,0
getbyte
Get a byte at given address.
print {getbyte:$9015} ; print the byte at $9015 in current bank.
getword
Get a word at given address.
print {getword:$9015} ; print the word at $9015 in current bank.
format
Format to a string
print {$04x:99} ; prints $0063.
textmap
Apply textmap to a string
db {textmap:"HELLO"} ; Works the same as text "HELLO"
astext
Force value to format value as text. Useful if you have a symbol displaying as an array.
test = "hello"
print test ; prints "test"
print {test} ; prints "[104, 101, 108, 108, 111]"
print {astext:test} ; prints "hello"
concat
Concatenate data.
print {concat:"foo","bar",0} ; prints "102,111,111,98,97,114,0"
sdasm
always 1
bank
current bank
lastbank
last prg bank
lastchr
last chr bank
banksize
current bank size
prgbanks
number of prg banks
chrbanks
number of chr banks
fileoffset
current file offset
year, month, day, hour, minute, second
appropriate numerical time value
randbyte
random byte
randword
random word
reptindex
loop index for a rept block
String values are partially supported.
foo = "bar" ; works
.db foo, "ABC", $00 ; works
lda "A" ; works
.db "ABC"+1 ; works (adds 1 to each character)
.db "A"+"A" ; does not work
| op | description |
|---|---|
| % | Modulo |
| & | Bitwise AND |
| ^ | Bitwise XOR |
| ~ | Invert |
| << | Shift bits left |
| >> | Shift bits right |
| ** | Exponentiation |
| * | multiplication |
| / | division |
| + | addition |
| - | subtraction |
| < | prefix to give lower byte of word |
| > | prefix to give upper byte of word |
Most directives may optionally be prefixed with a ".".
header / noheader
Used to indicate the rom contains a 16-byte iNES header. This is used
for calculating addresses.
header ; rom contains a header
noheader ; rom does not contain a header
stripheader
Used to indicate the rom contains a header, but it should be removed when
generating the final binary.
stripheader ; rom contains a header, but it should be removed after assembling.
= define
Used to define a symbol. Symbol names are case-insensitive by default.
foo = $42
define bar $43
org
Set the starting address if it hasn't been assigned yet, otherwise
org functions like pad.
org $8000 ; start assembling at $8000
.
.
.
org $fffa, $80 ;equivalent to PAD $fffa, $80
base
Set the program address. This is useful for relocatable code,
multiple code banks, etc.
base $8000
pad / fillto
Fill memory from the current address to a specified address. A fill
value may also be specified.
pad $FFFA
pad $FFFA, $ea
fill
Fill memory with specified number of bytes. A fill value may also be specified.
fill $20 ; output $20 bytes using current fillvalue
fill $20, $ff ; output $20 bytes using $ff
align
Fill memory from the current address to specified byte boundary. A fill
value may also be specified.
align 256
align 256, $ea
banksize
Set the size of each PRG bank.
chrsize
Set the size of each CHR bank.
bank
Set the current bank.
incbin "smb.nes"
banksize $8000
header
bank 0
org $9069
lda #$08 ; start with 9 lives
chr
Set the current chr bank. Internally, this will set the bank to the
chr area and adjust the address.
chr 0 ; Start of chr area
loadld65cfg
load a ld65 configuration file.
loadld65cfg "file.cfg" ; load and parse "file.cfg"
loadld65cfg ; use default filename "ld65.cfg"
segment
Set the current segment. Requires loading a ld65 configuration file first.
loadld65cfg ; use default filename "ld65.cfg"
segment "VECTORS" ; use defined segment "VECTORS"
fillvalue
Change the default filler for pad, align, etc.
fillvalue $ff
insert
Insert bytes at the current position. A fill value may also be specified.
insert $10 ; Insert $10 bytes using current fill value
insert $10, $ff ; Insert $10 bytes using $ff
delete
Delete bytes at the current position.
delete $10 ; Delete $10 bytes
truncate
Delete everything at or beyond current position.
truncate ; The file ends here now.
enum ende
Reassign PC and suppress assembly output. Useful for defining
variables in RAM.
enum $200
foo: db 0
foo2: db 0
enum
db / byte / byt / dc.b
Output bytes. Multiple items are separated by commas.
db $00, $01, $ff
dw / word / dbyt / dc.w
Output words. Multiple items are separated by commas.
dw $8012, $8340
dl
Similar to db, but outputs only the least significant byte of each value.
dl $8012, $8340 ; equivalent to db <$8012, <$8340
dh
Similar to db, but outputs only the most significant byte of each value.
dh $8012, $8340 ; equivalent to db >$8012, >$8340
dsb dsw
Define storage bytes or words. First argument is size, second is fill value.
dsb 4 ; equivalent to db 0, 0, 0, 0
dsb 4, $ff ; equivalent to db $ff, $ff, $ff, $ff
dsw 3, $1000 ; equivalent to dw $1000, $1000, $1000
hex
Compact way of laying out a table of hex values. Only raw hex values
are allowed, no expressions. Spaces can be used to separate numbers.
hex 456789ABCDEF ;equivalent to db $45,$67,$89,$AB,$CD,$EF
hex 0 1 23 4567 ;equivalent to db $00,$01,$23,$45,$67
include / incsrc / include? / require
Assemble another source file as if it were part of the source.
Include? will not generate an error if the file does not exist.
Require will abort assembly if the file does not exist.
include foobar.asm
include? optional.asm
require important.asm
includeall
Include all .asm files in a folder. Files starting with "_" will be ignored.
includeall code/macros
incbin / bin
Add a file to the assembly as raw data. A start offset and size may be
specified, as well as a symbol to fill the data with instead of adding it
to the output.
; include whole file
incbin "chr00.chr"
; include 32 bytes from file.dat starting at file offset 16.
incbin "file.dat", $10, $20
; get 32 bytes from file.dat starting at file offset 16 and
; fill the symbol "foobar" with it.
incbin "file.dat", $10, $20, foobar
incchr
Include an image file as chr data. The palette used should be set with
setpalette as an index of the palette loaded with loadpalette (or the
default palette, which is identical to FCEUX.pal).
setpalette $22, $16, $27, $18
chr 0
incchr "smbchr0.png"
incchr "smbchr0.png", 5, 2 ; include image starting at coordinates 5,2
incchr "smbchr0.png", 5, 2, 16, 1 ; include 16 columns and 1 row starting at coordinates 5,2
start tilemap ... end tilemap
Define a tilemap. Before the main tilemap entries, you can define gridsize, chr, org, palette.
gridsize = <size>
chr <chr page>
org <offset>
palette = <hexidecimal palette>
Each main entry uses hexidecimal for each tile id, x, y, and then flags of
either "h", "v", or "hv", to flip the tile horizontally, vertically, or both.
Note: Syntax of this directive will likely change to something more consistant.
start tilemap Mario_select1
gridsize = 1
chr $0c
org $0
palette = 0f271601
00 00 00
01 00 08
00 08 00 h
01 08 08 h
02 00 10
03 00 18
02 08 10 h
03 08 18 h
end tilemap
importmap exportmap
Import image file data using a tilemap. The tilemap may have its own chr bank, org, palette
set. exportmap works the same but exports using a tilemap to an image file.
importmap "Mario_select1", "Mario_select1.png" ; import using default coordinates (0,0)
importmap $00, $00, "Mario_select1", "Mario_select1.png" ; import using set coordinates
exportmap "Mario_select1", "Mario_select1.png" ; export using default coordinates (0,0)
exportmap $00, $00, "Mario_select1", "Mario_select1.png" ; export using set coordinates
assemble
Assemble a file. This is useful to assemble things in multiple stages, or to create a base
binary and include it conditionally, etc. The output file, etc can't be specified here, but
the directives to do so are available from the file to assemble.
assemble "test2.asm"
loadpalette
Load a palette file (.pal). Palette files should be 192 bytes--3 bytes per color, 64 colors.
loadpalette "FCEUX.pal"
loadtable / table
Load a table file (.tbl).
loadtable "text.tbl"
table text.tbl
cleartable
clear current text mapping.
cleartable
textmap clear ; This does the same thing as above
textmap
Create a textmap.
textmap set title ; Set current textmap to "title"
textmap clear ; clear current textmap
textmap abcd 00010203 ; Map characters a,b,c,d to $00,$01,$02,$03
textmap 0...9 00 ; Map characters from 0 to 9 to tiles starting at $00
textmap A...Z 0a ; Map characters A-Z to tiles starting at $0a
textmap space 24 ; Map a space to $24
outputfile
Set the output filename.
outputfile "game.nes"
listfile
Set the list filename.
outputfile "list.txt"
export
Export a symbol to a file.
; Write the contents of foobar to foobar.dat
export foobar, "foobar.dat"
diff
Generate a diff between the current data and a file.
diff original.nes ; display differences as asm data
diff original.nes, "data.asm" ; output differences to data.asm
ips
Apply IPS patch.
ips "patch.ips" ; apply ips patch.
Print a message
print Hello World!
warning
Print a warning message. The message will start with "Warning: ".
warning missing data!
error
Print an error message and stops the assembler. The message will start with "Error: ".
error file not found!
macro endm / endmacro
MACRO name args...
Define a macro. Macro arguments are separated by commas or spaces.
Note: symbols are not local.
macro setAXY x,y,z
lda #x
ldx #y
ldy #z
macro
setAXY $12,$34,$56
;expands to lda #$12
; ldx #$34
; ldy #$56
function endf / endfunction
Define a function. Function arguments are separated by commas.
Functions create a namespace with the function's name.
function splitByte(a)
; to access this symbol outside of this function
; use splitByte.foo or change the namespace with
; namespace splitByte
foo = 42
return >a, <a
endfunction
h,l = splitByte($42)
if ifdef elseif else endif
Process a block of code if an expression is true (nonzero).
if foobar = 3
db 0
elseif foobar = 5
db 1
else
db $ff
endif
ifdef / ifndef elseif else endif
ifdef will process a block of code if a symbol has been defined.
ifndef will process a block of code if a symbol has not been defined.
ifdef foobar
db foobar
else
db 0
endif
iffileexist / iffile elseif else endif
Process a block of code if given file exists.
macro includeIfExist _file
iffile {_file}
include {_file}
endif
endm
includeIfExist file.asm
seed
Set the random number seed for use with anything that uses random values.
seed $42
db {shuffle:$00, $01, $02, $03, $04, $05}
mapdb
Allows db directive to map text like the text directive.
mapdb ; turn on
mapdb on ; turn on
mapdb true ; turn on
mapdb 1 ; turn on
mapdb off ; turn off
mapdb false ; turn off
mapdb 0 ; turn off
clampdb
Allows db directive to use numbers outside of byte range, clamping them to fit.
clampdb ; turn on
clampdb on ; turn on
clampdb true ; turn on
clampdb 1 ; turn on
clampdb off ; turn off
clampdb false ; turn off
clampdb 0 ; turn off
rept endr / endrept
Repeat block of code specified number of times.
The special symbol {reptindex} can be used to get the loop index.
Recursion is currently not supported.
rept 5
print This is rept loop {reptindex}.
endr
findtext
Search for text using the current textmap, starting at the current position.
If found, the resulting bank and address will be printed, and the symbols
"resultbank" and "resultaddress" will be filled. If not found, the symbols
will be false.
lastpass ; skip to final pass
lastpass
Skip to final pass. This will likely cause issues, but can be useful if you
know the result will be ok.
lastpass ; skip to final pass