Looking for a 6502 disassembler for reverse engineering

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bprosman
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Looking for a 6502 disassembler for reverse engineering

Post by bprosman » Sat Dec 29, 2018 10:16 am

Helping someone to reverse engineer a 6502 SBC. It has a 6052 processor, a 2K EPROM from F800-FFF, and a 2K Ram and 6522 "somewhere in the memory map". The memory decoding prom (82S129) is still to be read.
Any suggestion of a disassembler/emulator ?. I have the monitor in .HEX and .BIN format. For the rest no docuentation whatsoever.

Googling on MPS65 doesnt bring me anythig

Thanks in advance, Bram
Ian_Day_6502_solder.jpg
Ian_Day_6502_components.jpg

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Pernod
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Re: Looking for a 6502 disassembler for reverse engineering

Post by Pernod » Sat Dec 29, 2018 11:12 am

What are you trying to find out about it?

If you post the monitor then I could create a simple driver in MAME for it.

Same board is also discussed at http://forum.6502.org/viewtopic.php?f=3&t=3023
Last edited by Pernod on Sat Dec 29, 2018 11:32 am, edited 1 time in total.
- Nigel

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BigEd
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Re: Looking for a 6502 disassembler for reverse engineering

Post by BigEd » Sat Dec 29, 2018 11:27 am

Looks like a machine somewhat like this is the subject of this thread, which includes a ROM dump: As for a disassembler, there are many listed here, but this one might be a good start:

bprosman
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Re: Looking for a 6502 disassembler for reverse engineering

Post by bprosman » Sat Dec 29, 2018 11:34 am

Thanks for the responses so far, looks indeed like the same board.
What are you trying to find out about it?
Try to reverse engineer it.

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BigEd
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Re: Looking for a 6502 disassembler for reverse engineering

Post by BigEd » Sat Dec 29, 2018 11:50 am

I'll be interested to see the results! I see the auction listing over on 6502.org promises some notes on how to use the monitor - I suppose you don't any documentation at all?

It's a nice board, two sided, through hole, and a big multi-way connector for expansion.

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Pernod
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Re: Looking for a 6502 disassembler for reverse engineering

Post by Pernod » Sat Dec 29, 2018 12:26 pm

I have the ROM from the other forum running, the 6522 is at A000-A00F, and it's also expecting something at E003.

No keyboard or LED output yet so nothing to show.
- Nigel

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hansotten
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Re: Looking for a 6502 disassembler for reverse engineering

Post by hansotten » Sat Dec 29, 2018 6:10 pm

Some more info (its a Facebook discussion at 6502 Homebrew Hardware and Programming group where Bram and I participate about this SBC, photos and video shown while operating, now broken)

The memory decode PROM has been read out by the owner Ian Day

00000000 -> 0 -> 1011
00000001 -> 1 -> 1011
00000010 -> 2 -> 1011
00000011 -> 3 -> 1011
00000100 -> 4 -> 1011
00000101 -> 5 -> 1011
00000110 -> 6 -> 1011
00000111 -> 7 -> 1011

10100000 -> 160 -> 1101

11110000 -> 240 -> 0111
11110001 -> 241 -> 0111
11110010 -> 242 -> 0111
11110011 -> 243 -> 0111
11110100 -> 244 -> 0111
11110101 -> 245 -> 0111
11110110 -> 246 -> 0111
11110111 -> 247 -> 0111
11111000 -> 248 -> 0111
11111001 -> 249 -> 0111
11111010 -> 250 -> 0111
11111011 -> 251 -> 0111
11111100 -> 252 -> 0111
11111101 -> 253 -> 0111
11111110 -> 254 -> 0111
11111111 -> 255 -> 0111

So three Chip select lines, unknown which one is RAM or ROM. The one liner will be the 6522.

I looked at the disassembled ROM dump from 6502.org, I see the 6522 at address A000. I did not see other I/O yet.

What I see from the disassembly and the photos is:
65C02 at 2 MHz
RAM 6116 2K at 0000
6522 at A000
ROM 2K at F800 (pure 6502 code afaik in the ROM)
24 key keyboard/ 6 led matrix with 7400 and 7442 decoder and transistor for every led display
RS307-109 Darligton Driver Array
82S129 as show above
Transistor for reset?
Last edited by hansotten on Sat Dec 29, 2018 6:10 pm, edited 1 time in total.

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jgharston
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Re: Looking for a 6502 disassembler for reverse engineering

Post by jgharston » Sun Dec 30, 2018 1:38 am

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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jms2
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Re: Looking for a 6502 disassembler for reverse engineering

Post by jms2 » Sun Dec 30, 2018 9:00 am

Jonathan, the MkSrc.txt file on that page is a dead link - which is a pity because I'd be interested to try out mksrc65. I've never found any program which allows you to interactively disassemble 6502 code such that you end up with usable source code, but it looks like this might do it.

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hoglet
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Re: Looking for a 6502 disassembler for reverse engineering

Post by hoglet » Sun Dec 30, 2018 9:07 am

jms2 wrote:
Sun Dec 30, 2018 9:00 am
I've never found any program which allows you to interactively disassemble 6502 code such that you end up with usable source code, but it looks like this might do it.
Phill's BeebDIS is pretty good.
viewtopic.php?t=14979

Dave

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BigEd
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Re: Looking for a 6502 disassembler for reverse engineering

Post by BigEd » Sun Dec 30, 2018 1:26 pm

FYI, Arne has just posted some (German) PDFs in the thread over on 6502.org.
BigEd wrote:
Sat Dec 29, 2018 11:27 am
Looks like a machine somewhat like this is the subject of this thread, which includes a ROM dump:

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jgharston
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Re: Looking for a 6502 disassembler for reverse engineering

Post by jgharston » Mon Dec 31, 2018 6:39 am

jms2 wrote:
Sun Dec 30, 2018 9:00 am
Jonathan, the MkSrc.txt file on that page is a dead link - which is a pity because I'd be interested to try out mksrc65. I've never found any program which allows you to interactively disassemble 6502 code such that you end up with usable source code, but it looks like this might do it.
Fixed.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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