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Post by Syntesis on May 1, 2012 16:59:53 GMT
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Post by buckoa51 on May 1, 2012 17:26:18 GMT
Suitable for what exactly? That's for PIC's and not Eproms if that's what you're wondering.
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metalhead
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Post by metalhead on May 1, 2012 18:55:21 GMT
Will do the job for making switchless Saturn mods if that's what you mean but as buckoa51 said it won't do anything other than PIC chips.
Pretty good for £8.95 though.
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Post by Syntesis on May 1, 2012 20:26:09 GMT
Yep just for switchless mods for various consoles. Being able to program Eproms would be nice but that would be a lot more expensive and this little device is going on somebody else's tab.  |
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Post by zyrobs on May 1, 2012 22:44:23 GMT
So you could build your own modchip with that?
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metalhead
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Post by metalhead on May 2, 2012 16:03:45 GMT
So you could build your own modchip with that? Saturn modchips use an EECMOS IC and although I'm not completely understanding on these chips, a PIC programmer wouldn't be capable of reading/programming them. You can buy more expensive universal IC programmers that are like Swiss Army Knives and do everything at a high price of course. Quite often, though these ICs are encrypted in such a way that you can't just read their contents back and dump it as hex. For example disassembling one of Rob Webb's chips and attempting to extract the code probably would not work. I think there are four ICs used in a modchip along with a clock crystal and other discrete parts. Producing a custom PCB for something like this is normally beyond the scope of the home enthusiast. However, the above linked programmer would be perfectly capable of programming the 16F630 PIC required for Seb's switchless mod. |
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Post by zyrobs on May 2, 2012 16:56:34 GMT
aaah, you're right, I thought the chips are controlled by the pic16's on them, but most of them also have another programmable chip on them. Even if the PIC16C54 can be replicated, I guess the other chip cannot, right?
There are over a dozen different modchips, and not all work in all machines. Some of them are wired up to both 20pin and 21pin ones. The least complex ones I've seen use only 2 ICs, and maybe two resistors. I'm slowly trying to buy one of each chip and test it with my hardware, but I don't yet have the last revision drive, which DOES need different settings on some chips.
One thing I've wondered about - some chips include a 8mhz external clock crystal. But, the saturn drive itself sends a 8mhz clock signal as well. Wouldn't this make the crystal redundant?
The last batch of chips I got are all wired up to use this signal from the ribbon cable, BUT the traces are cut on the board and there's another signal wire soldered on leading to the same pin as the original trace did. It looks pretty damn stupid since the chip leg you have to solder the cable to is the one that actually leads to that cut trace from the ribbon cable...
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EverestX
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Post by EverestX on May 3, 2012 7:03:45 GMT
One thing I've wondered about - some chips include a 8mhz external clock crystal. But, the saturn drive itself sends a 8mhz clock signal as well. Wouldn't this make the crystal redundant? If I recall correctly, all the old chips had Xtals, newer revisions generally do not have a crystal installed. Some years later the 'A+B' trick was identified in order to source the signal directly from the system, it was years ago, but I believe you can dig it up on sega xtreme. For example, the newer chips don't have a discreet Xtal (Should be located on PCB where '8.467mhz' is printed:  --It's worth noting (and I haven't bothered to check) but the other IC's on the newer designed chips may be provided by an internal clock, which would explain why the discreet isn't provided, however I don't believe that's the case. |
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Post by zyrobs on May 3, 2012 12:05:15 GMT
I know of that trick. What I mean is: the signal wire is supposed to be connected to the xtal out pin on the cdrom controller. BUT that very same pin is also connected straight into the ribbon, pin 21 to be exact. So adding that wire is completely redundant. In fact I've seen and have a couple of chips which have traces on them, leading pin21 of the ribbon into the main components, but this trace is cut, and instead a wire is soldered to the same location that you must connect to the cdrom controller xtal out pin....
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metalhead
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Post by metalhead on May 3, 2012 15:43:12 GMT
One thing I've wondered about - some chips include a 8mhz external clock crystal. But, the saturn drive itself sends a 8mhz clock signal as well. Wouldn't this make the crystal redundant? I'm guessing the reason for this is that the Saturn requires precise timing when sending/receiving the check code provided by the modchip. Whilst PICs do have their own internal clock it probably isn't accurate enough to work 100%. As I say I'm only speculating. If I knew the secret to the way modchips were designed I'd be knocking them out myself lol! ;D |
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