6502 Assembler

src:	listing:


object code:

Show the 6502 Instruction Set.
Show the virtual 6502 emulator.
Show the 6502 Disassembler

Instructions

This is is simple 2 pass assembler for the 65xx micro processor.
It is thought to accompany the virtual 6502 emulator.

To get your source code compiled:

Enter your source code in the "src" pane.
Click the button "generate code".
Watch the progress in the "listing" pane.
Copy any generated code from the "object code" pane.
(This can be pasted directly into the virtual 6502 emulator's memory pannel.)

Syntax

The assembler supports the following syntax:

Opcodes and Addressing
	Instructions are always 3 letter mnemonics followed by an (optional) operand/address:

OPC	....	implied
OPC A	....	Accumulator
OPC #BB	....	immediate
OPC HHLL	....	absolute
OPC HHLL,X	....	absolute, X-indexed
OPC HHLL,Y	....	absolute, Y-indexed
OPC *LL	....	zeropage
OPC *LL,X	....	zeropage, X-indexed
OPC *LL,Y	....	zeropage, Y-indexed
OPC (BB,X)	....	X-indexed, indirect
OPC (LL),Y	....	indirect, Y-indexed
OPC (HHLL)	....	indirect
OPC BB	....	relative

Where HHLL is a 16 bit word and LL or BB a 8 bit byte, and A is literal "A".
There must not be any white space in any part of an instruction's address.

Number Formats
	$[0-9A-Zaz]	....	hex
	%[01]	....	binary
	0[0-7]	....	octal
	[0-9]	....	decimal
	<	....	LO-byte portion
	>	....	HI-byte portion

Labels and Identifiers
	Identifiers must begin with a letter [A-Z] and contain letters, digits, and the underscore [A-Z0-9_]. Only the first 6 characters are significant. All identifiers, numbers, opcodes, and pragmas are case insensitive and translated to upper case. Identifiers must not be the same as valid opcodes. The special identifier "*" refers to the program counter (PC).

Exampels:
* = $C000	....	Set start address (PC) to C000.
LABEL1 LDA #4	....	Define LABEL1 with the address of instruction LDA.
BNE LABEL2	....	Jump to address of label LABEL2.
STORE = $0800	....	Define STORE with value 0800.
HERE = *	....	Define HERE with current address (PC).
HERE2	....	Define HERE2 with current address (PC).
LDA #<VAL1	....	Load LO-byte of VAL1.

Pragmas
	Pragmas start with a dot (.) and must be the only expression in a line:
	.BYTE BB	....	Insert 8 bit byte at current address into code.
	.WORD HHLL	....	Insert 16 bit word at current address into code.
	.END	....	End of source, stop assembly. (optional)

Comments
	; comment	....	Any sequence of characters starting with a semicolon till the end of the line are ignored.

White Space
	The assembler does not rely on any special formatting with the following exclusion: There must be white space between a label and a opcode and the opcode and any operands. Only one instruction per line is permitted.

Code Example
	Src:	Listing:

	Object Code:

Disclaimer:
This program is provided for free and AS IS, therefore without any warranty;
without even the implied warranty of merchantability or fitness for a particular purpose.

Links:
The official 65xx Website (The Western Design Center Inc.): www.65xx.com