WinASM65

Assembler for 6502 based systems by CodewinBzn.

---

Command line

Usage

	WinASM65 [-option] sourcefile

Options

	-help			Show help
	-h			Show help	
        -l 			Create listing (don't specify the file name)
	-c 			Assemble one or multiple segments
				Combine assembled segments/binary files
Assemble single segment:
	-f			Source file 
	-o			Object file

Assemble segments

JSON File format

{
	"Input": [
		  	{
				"FileName": "path_to_main_file_seg1",
				"OutputFile": "path_to_seg1_output_file",
				"Dependencies": ["path_to_main_file_seg2"]
		  	},
		  	{
				"FileName": "path_to_main_file_seg2",*
				"OutputFile": "path_to_seg2_output_file",
				"Dependencies": ["path_to_main_file_seg1"]			
		  	},
	          	{
				"FileName": "path_to_main_file_seg3",
				"OutputFile": "path_to_seg3_output_file",
				"Dependencies": []			
		  	},
		   	......
		]
}

Dependencies

If a segment refers to labels, variables ... or to routines declared in other segments then it must mention them in this array as ["path_to_main_file_seg1", .....].

OutputFile

The OutputFile is optional.

Combine assembled segments / Binary files

JSON File format:

{
	"Output": { 	
			"ObjectFile": "final_object_file",
			"Files": 
			[
				{
					"FileName": "path_to_seg1_output_file",
					"Size": "$hex"
				},
				{
					"FileName": "path_to_seg2_output_file",
					"Size": "$hex"
				},
				{
					"FileName": "path_to_seg3_output_file"			
				},
				....
			]
		}
}

The Segments are declared in the order of their insertion in the final object file.

Size

The size of the segment object file. If the size of the assembled segment is less then the declared size then the assembler will fill the rest of bytes with the value $00 .

Syntax

• Comments begin with a semicolon (;).

lda #$00 	; this is a comment

• Labels are declared in two ways.

• before an instruction

			ldx #$00
	label 	        lda $4000, x
			cpx #$10
			bne label

• Alone in a line, A colon (:) following a label is mandatory

		ldx #$00
label:
	 	lda $4000, x
		cpx #$10
		bne label

Numbers

• Hexadecimal numbers begin with '$'.
• Binary numbers begin with '%'.
• Decimal.

Assembler directives

.ORG / .org

• Set the starting address of a segment.
• To use only once in each segment.
• Accepts expressions.

	.org $c000
lda #$00	

.MEMAREA / .memarea

• Set the starting address of a memory area for memory reservation (accepts expressions).

.RES / .res

Reserve a number of bytes (accepts expressions).

	.memarea $00  ; zero page
player_posx  .res 1
player_pos_y .res 1

ram = $0400
	.memarea ram
nbr_coins = 15	
coins_pos_x .res nbr_coins  ; to store posx of coins  
coins_pos_y .res nbr_coins  ; to store posy of coins

.INCBIN / .incbin

• Add the content of a binary file to the assembly output.

.incbin "path_to_binary_file"

.INCLUDE / .include

• Assemble another source file as if it were part of the current source.

.include "path_to_source_file"

.BYTE/.byte, .WORD/.word

• Emit byte(s) or word(s).
• Multiple arguments are separated by commas.
• Accept expressions.

RED = $06
palette:
.byte $00, $10, RED + 4, $5d

Strings

lda #"A"

.byte "A", "B"
.byte "NES"
myString: 
	.byte "Hello World"		

.IFDEF/.ifdef, .IFNDEF/.ifndef

Conditional assembly

• Process a block of code if a symbol has been defined / not defined.

.ifdef _debug_
	.
	.
	.
.else 
	.
	.
	.
.endif

.IF/.if

Conditional assembly

• Process a block of code if the logical expression is evaluated to true.
• The expression must be a constant expression, that is, all operands must be defined.

.if expression
	.
	.
	.
.else 
	.
	.
	.
.endif

.MACRO/.macro

• Define a macro. Macro arguments are comma separated.
• .macro name args...

.macro add @a, @b
	clc 
	lda @a
	adc @b
.endmacro

red_color = $85
add #red_color, #$00	

.REP/.ENDREP

• Repeat a block of code constant number of times.
• The command is followed by a constant expression that tells how many times the commands in the body should get repeated.

;clear memory
clrmem:
  LDA #$00
  {
    mem = $0000
    .rep 8
      STA mem, x
      mem = mem + $0100
    .endrep  
  }
  INX
  BNE clrmem

;fill the remaining bytes of the bank
lastbyte:
.rep $2000 - (lastbyte - $c000) 
	.byte $ff
.endrep

.END/.end

• Forced end of assembly. Assembly stops at this point, even if the command is read from an include file.

Expressions

Supported operators (listed by precedence)

 - ()
 - + - ~ ! < > (The unary < and > give respectively the lower and the upper byte of a value)
 - * / %
 - + -
 - << >>
 - < > <= >=
 - = == != <> 
 - &
 - ^
 - |
 - &&
 - ||
 - #   	    	 Immidate addressing.

Local lexical level

.macro vblank label, register
   label: 
   	BIT register
   	BPL label
.endmacro
.
.
.
{ ; All new symbols from now on are in the local lexical level and are not accessible from outside.
  ; Symbols defined outside this local level may be accessed as long as their names are not used for new symbols inside the level.
  ; Macro names are always in the global level.
  
  vblank vblankwait, $2002
}
.
.
.
{   
   vblank vblankwait, $2002   ; Second wait for vblank, PPU is ready after this
}