d6502 - a compact 6502 disassembler in 100 lines of code

[oog]

This is a compact disassembler for the 6502 CPU in just 100 lines of code (plus data tables for opcodes and rom image in separate include-files).

The program has a simple shell. Commands are typed in as single letter instructions. They are almost "TEDMON"- compatible. The address pointer is initially set to the RESET-vector from the ROM image file. A real 6502 CPU would start here after a reset.

There is a demo ROM image included, which starts at hex FE00 and is simply filled with all defined 6502 opcodes. You can simply press Enter to disassemble the next line of opcode.

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'd' [<ADDR>]: disassemble, '': disassemble next line, 'x': exit

.FE00  00        BRK
.FE01  01 12     ORA ($12,X)
.FE03  05 12     ORA $12
.FE05  06 12     ASL $12
.FE07  08        PHP
.FE08  09 12     ORA #$12
.FE0A  0A        ASL
.FE0B  0D 12 34  ORA $3412
.FE0E  0E 12 34  ASL $3412
.FE11  10 12     BPL $FE25
FE13

Some notes for the background of this project

I did build a 2 MByte RAM expansion board for a Microcontroller, that originally has just 2 kilobytes (ATMEGA 328 on an Arduino Nano board). I took the RAM chips from an old PC EDO DIMM module. The RAM expansion module works fine and needs just 12 portbits for the connection. However, it can't expand the internal RAM of the microcontroller - the necessary signals are not available outside of the microcontroller IC. The RAM is just available with special load and store functions via port pins.
So I use a 6502 CPU emulation, which has simulated native access to the external RAM module.



edit: link to image.

[oog]

Upps, can not post code. Get this message:

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Forbidden
Access to this resource on the server is denied!

edit: Download sourcecode here: http://proog.de/dl/d6502/dl_d6502.zip

[srvaldez]

nice :-)

[oog]

da6502 - a compact 6502 disassembler with assembler.


Added 6502 assembler to the code and renamed file to "da6502", "da" = disassembler / assembler.

To start the assembler, type the letter 'a' an a startaddress for the code.

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Example: a 1000

The assembler shell starts up. You see the actual address ($1000 in this example) and an input prompt next to it. You can directly type in your code. Every line of code will be assembled and checked immediately.
To stop assembling, just press enter in an empty line.

Example:

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	lda #$f0
	clc
	adc #20	; the decimal 20 will be converted into hex
	pha
	nop
			; press enter without any input to close the assembler shell

You can now disassemble your program by typing

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d 1000

New Download is here:

http://proog.de/dl/d6502/dl_da6502.zip

Have fun.

[D.J.Peters]

Looks like you have some fun with this stuf :-)
From time to time I "play" with my Motorola IC's from the 70'
and yes my MC6801/2/3 disassembler assembler are written in FreeBASIC also.

Joshy

[h4tt3n]

Nice project :-)

[StillLearning]

Where do you download this code now?