Hi,

I've just been lumped with a bunch of reverse engineering on a "UM6561CF-2." It is some form of 6502 vairant, but that is ALL I can find out on it.

I am getting blinded with instruction set vairants, and five hundred different ways of failing to describe (well) the addressing modes.

Can anybody point me toward the right answers.
# What instructions are avilable on UM6561CF-2
# Human readble description of it's addressing modes

thanks for any help guys,

BC

Have you got a dump of the ROM we could have a look at? It may help deciding which 6502 type it is.

Lee.

The original can be found here:
http://n64.icequake.net/mirror/64scener ... /black.zip

The image is
64k=6502 rom + 64K=n64 util
128K=copy of the above

If you would rather the file were uploaded here, please ask :)

After unzipping, my computer doesn't seem to know how to open the file your link pointed to, but the 6561 in my Commodore data sheets is a PAL video interface chip with on-chip color generation, 192x200-dot screen size, two character sizes, light pen, two 8-bit A/D converters, three independent programmable tone generators, a white noise generator, and an amplitude modulator, among other features. The 6560 is the NTSC version. AFAIK, the processor numbers were always much lower, like 6504, 6507, etc., except some microcontrollers that were much higher, like 65151, 65134, 65265, etc..

so far i understand that the first 64k of the image is the 6502 rom image,

execution seems to start 0x1'0000 into the image -
this is only because v1.1 opf the firmware looks like this:
....oh - can't attach files - damn!

well... there is ONE block of code, that starts at 0x1'0000
and the code at 0x1'0000 has the (c) message in it, which pops up on boot.

the second 64K is NOT 6502 code (it is MIPS r4000 code)

the last 128K of the image is a clone of the first 128K - no idea why ...yet.

The rom sits at 0x8000 - as expected and confirmed by others on the team

any help?

Those are Commodore-specific part numbers. For example, Hifn has a chip called the 6500, which contrary to popular belief, is NOT a 6500- or 6502-clone. It's a 1024-bit integer, modular math coprocessor. (I know, 'cos I helped verify the chip's correctness when I worked for them. ).

I think this is why Intel decided against calling their subsequent lines of chips the 80586, 80686, etc -- part numbers mean nothing in the grand scheme of things. The only reason the 6502 is as well known is because back when it first came out, the contention for part numbers wasn't as tight as it is today. Now-a-days, especially with Commodore out of business, I could easily make a part called the FK6561, or some such, and it would be of absolutely no relationship to either the 6502 or the infamous VIC-I chip.

The 6502 starts executing code whereever its RESET vector tells it. But the 6502 MUST have RAM to address for zero-page and stack address modes too. Hence, that ROM image you have is banked. That is, only specific segments of the image are visible to the CPU at any given time.



I'm not sure how we can help you. 6502.org has 65C816 and 65C02 data sheets available on the site; westerndesigncenter.com has a book available for order that contains "human-readable" addressing modes, as you put them, though most any document on the net about programming the Commodore 64 will include some kind of introduction to its 6510 CPU, which is just a 6502 with an internal port used for memory mapping control and casette access.

It's the Nintendo-specific extensions to the 6502 that will be the hardest to diagnose, but can be figured out the same way people figured out the use of undocumented opcodes in the 6510A CPU:

1. Set up a well-known and self-consistent initial set of conditions,
2. Execute the unknown opcode, and
3. Examine the environment for differences, including effects on CPU registers.

--
Samuel A. Falvo II

>>I'm not sure how we can help you.

Well, I'd love to know "What instructions are avilable on UM6561CF-2"
Someone Somewhere must know - just wondered if he lived here.

>>It's the Nintendo-specific extensions to the 6502 that will be the hardest to diagnose

This is NOT a Nintendo device - If I put a JPG in the second bank of ROM, it will not become a photograph album either. ;)

Thanks for the hacking tips ...If nobody knows what instrcution set variant this processor uses, I will buid an ICE an take a look :)

I am slowly piecing together all the contradictory information on addressing modes, I'm sure I'll work it out soon enough - not my first or my last chip ;)

Cheers again

BC

Your analogy doesn't make sense. How do you know that chip wasn't custom commissioned by Nintendo? Nobody except the eggheads in Nintendo would be able to answer that. This sort of thing happens all the time.

Anyway, Google reports that this chip was made by a company called UMC, in Taiwan.

http://216.239.53.104/search?q=cache:lO ... n&ie=UTF-8

But I doubt that it's very popular, or even still in production -- Looking for UM6561 gives mostly bogus webpages, and absolutely no details on its instruction set.

--
Samuel A. Falvo II

>> How do you know that chip wasn't custom commissioned by Nintendo?

One could never know for sure. But given that the company that made the device which contains this chip was sued out of business by Nintendo, it seems very unlikely <shrugs>

Yyyyeeessss.....that would be a GOOD indicator that Nintendo didn't commission the chip from them. Not certain, but good..

Just thought I'd throw this in.

I have in my beloved collection of 6502s and variants, a UMC-made 6502. The part number is indeed 6502. I'll have to go home and look to get the full part number, but it is a 6502, not a 6561. UMC from what little research I was able to do, UMC is a Chinese company. They have a web site: www.umc.com. The chip you have has a little planet with some lattitude/longitude lines on it for a logo, correct? That's what I have on my 6502.

My guess is that the 6561 is not a CPU at all, but a peripheral chip. If it is a CPU, it is probably UMC's own variant and you're not likely to find much reference on it.

Scott

Thanks for everyone's help - if I ever find the anything on it - i will report back - nice forum guys, keep up the good work :)