Dumping a NES cartridge

 General  Comments Off on Dumping a NES cartridge
Aug 112014
 

Recently I offered to help out someone wanting his Super Adventure Quests NES cartridge dumped.
I was quite surprised at first as I thought all NES carts had already been dumped but apparently not.

Here is the cartridge in question.
IMAG0749
IMAG0748

This is the same as the already dumped cartridge of Quattro Adventures. This was the NTSC release where as Super Adventure Quests was the PAL release.
The whole reason this dump in particular was wanted is because the NTSC release doesn’t work on a real PAL console using the Everdrive cartridge.

I got hold of this cart and decided the best and quickest way of dumping it was to desolder the ROM chip and read it out.
IMAG0754

I looked online and the very small amount of information I could find suggested it was most likely a 23C2001 MASKROM pinout. As my programmer has support for this device it should have been good to go.
Well it didn’t work so after mapping out the connections on the PCB it looks like the pinout is the same as a 27C020.
This worked just fine.

Copying the iNES header from Quattro Adventures and prepending it onto my ROM allowed me to load it up in emulators to check it.
nestopia

Job done. This has now been added to MESS.

X Multiply RAM errors

 General, Technical Info  1 Response »
Jul 202014
 

At the moment I have an X Multiply PCB that shows a “RAM NG 10” error on startup.
Although I have yet to find the problem with this board I thought it best to find out exactly what RAMs these errors are referring to.
To make any sense of this you will need the memory map for the game found in M72.C file of the MAME source code.

Here is a short list of what I have found so far:
0x9c000-0x9ffff = RAM NG 1 (Work RAM)
0xc0000-0xc03ff = RAM NG 10 (Sprite RAM)
0xc8000-0xc8bff = RAM NG 9 (Palette RAM 1)
0xcc000-0xccbff = RAM NG 8 (Palette RAM 2)
0xd0000-0xd3fff = RAM NG (Video RAM 1)
0xd8000-0xdbfff = RAM NG (Video RAM 2)

 Posted by at 8:30 pm

Cheap and easy -5v

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Jul 152014
 

Its becoming more and more common for power supplies to not supply -5v.
There are devices out there like the “Negatron” that offer a nice and easy way to obtain an adjustable -5v but there is a much cheaper way of getting it providing you can do a little bit of soldering.
Intersil offer a 7660 voltage converter IC. Its an 8 pin DIP device that can be bought for under £1 from Farnell and other places.
Farnell – ICL7660

I bought a couple of these on a recent order to test and the results, as expected, are great.
This is it setup on breadboard.
IMAG0673

IMAG0674

All that’s required is a +5v input, the ICL7660 IC and 2 x 10uF capacitors to get a -5v output. Add a variable resistor into the mix and you have a fully adjustable device for very cheap.
Here is the diagram lifted straight from the datasheet to show how simple this is.
icl7660

 Posted by at 9:16 pm

Konami 007644 custom chip

 General, Technical Info  Comments Off on Konami 007644 custom chip
Jun 132014
 

Ive got a board that needs a new 007644 custom chip.
While im waiting to find a new one I thought I would investigate how this chip actually works.

Pin 1 = SEL – changes whether the Q outputs require a rising edge clock or not.
Pin 2 = OEY – Output enable for the Y outputs else they are inputs. Active LOW
Pin 21 = OEQ – Output enable for the Q (clocked) outputs else they are inputs. Active LOW
Pin 12 = CLK – Clock input

Pins 3-10 = Y outputs – normal outputs. If OEY is LOW these pins become outputs mirroring the state of the Q input pins. SEL and CLK pins are not used in this mode.

Pins 13-20 = Q outputs – clocked outputs. If OEQ is LOW these pins become outputs. If SEL is HIGH and CLK is HIGH these outputs will mirror the state of the Y inputs. If SEL is LOW then the outputs will only change state on a rising edge CLK.

Pretty simple and should be easy to implement in a small CPLD if ever required (next project???)

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