Credit board & MV1C schematics

I'm searching for two things on the forums and google with no luck at all:

1.- I would like to include a led credit board on a CMVS, but I have no knowledge about credit boards. Long time ago I saw some very simple to build by myself, with two led digits, but unfortunately that board got lost. Anyone can help?

2.- I also have to repair a bunch of MV1C Neos and it is a real pain to follow all the traces without having a proper schematic. Does anyone have one to share? I'm building one, if it can help someone. The coloured dots are the logic probe state on that pin on normal crosshatch. The nomenclature is easy: chip name and pin number. I've started from the BIOS, but my idea is to do the pinout for every main chip. It is not very proffessional, but I can read it quickly:



Any help will be appreciated. Thanks.

It seems that SNK never released the schematics for this board (they did for the mv1f, I have it). If someone have some spare time to follow traces and publish it here, it would be great for the repair community...

Some pinouts for SNK chips: http://neogeodev.wikkii.com/wiki/Category:Chips

MV1F schematics: (oops, maybe not a good idea)

furrtek said:

Some pinouts for SNK chips: http://neogeodev.wikkii.com/wiki/Category:Chips

MV1F schematics: (oops, maybe not a good idea)

Click to expand...

Thank you, I already know that site.
I keep making the manual trace following and probe logic... will publish it if someone ask for it (seems that no one is interested on it).
About the credit counter, I have no clues.

The pinouts would be a nice addition to the wiki. Maybe no one reading this thread has an immediate need for it but having it available there when someone might find it useful would be cool.

Can always be interesting yes, not sure what are the differences are between the 1-slot boards. Will keep an eye on this thread
I'm curious to see how do you handle burried traces, the MV1C is a 4 layer board, right ?

Seems you already picked up the GRZ, DCR and YSA connections to the 68k bus.

Hey guys,

Since I was asked in PM about the credit board, I figure I might as well put the theory of operation on the credit pcb. Please note I didn't use formal schematics for this board like I am with other boards. I'll get around to making schematics eventually

There are 13 pins on the MV-LED board.
2 pins are +5V, 2 pins are GND
1 is a clock signal, and 8 are data signals.
If my memory serves me correctly, the 1 clock signal is pin 3, d0 is pin 4, d1 is pin 5..etc.

There is a filter cap, (I think its 12V 220uF?) on the board for power noise reduction.
Each IC has a 1uF bypass cap.

All signals have pull-up resistors on them at the connector. Ie, CLK, D7-D0 have pull-up resistors.

The clock signal is routed through the 74HC14AP two times. Since this inverts the clock and then re-inverts the clock, I think the reasoning is for noise reduction. The rest of the unused inputs on the 74HC14AP are tied to the unused outputs since this is a CMOS device. No input pins on a CMOS device should be left floating.

The D flip flop's (HC273) input clock is tied to the clock mentioned above. The 8 data lines connect to the 8 D inputs. The 8 Q outpus connect to the 7 segment driver IC's. 4 go to one IC, 4 go to the other IC. Each one connects to A,B,C,D inputs.

The a,b,c,d,e,f,g outputs on each of the 7 segment drivers connect to 330 ohm series resistors (current limiting resistors). Then they connect to the two-digit common anode 7-segment display. The bits d0-d3 drive the number on the RIGHT, and bits d4-d7 drive the number on the LEFT.

*EDIT*:
For the 74LS47N that controls the LEFT 7 segment digit, *BI/RBO must be left unconnected. *RBI must be connected to GND. *LT can be tied to logic 1. All of these control signals can be tied to VCC on the 74LS47N that control the RIGHT 7 segment digit.

This is all from memory, so there may be small inaccuracies.

jakeus said:

Please note:
There is some way they made it so the "left" number does not illuminate when the count is single digit. Right now my display shows "00", "01", "02", where as theirs shows " 1", " 2", " 3" Given the circuit, I'm not quite sure why they chose to do this in hardware versus software. I have to run more simulations to figure that out.

Click to expand...

not to derail but....
i do believe it's due to the /RBI on the 7447 is set low for the high digit, and is tied to /LT (high) on the low digit. sorry if i'm stating the obvious. did you do this and it still displays the leading zero?
imho, as for doing this via hardware, there is a lot of noise reduction on this little board. i would assume since there is a rather long harness to these boards from the mobo, noise can be a big issue. therefore i would assume that it would be necessary to clean up the signal at the end to display the digits properly. rather, just having a board with 2x 7segs (+resistors) it might display a noisy signal. am i wrong? pretty text book BCD to 7 seg decoder, nice write up post btw.

stupid question though: what are the "RRC" components (near the header) on the credit counter board? i can't find that part number anywhere. am i missing something obvious?

xhiltch said:

not to derail but....
i do believe it's due to the /RBI on the 7447 is set low for the high digit, and is tied to /LT (high) on the low digit. sorry if i'm stating the obvious. did you do this and it still displays the leading zero?
imho, as for doing this via hardware, there is a lot of noise reduction on this little board. i would assume since there is a rather long harness to these boards from the mobo, noise can be a big issue. therefore i would assume that it would be necessary to clean up the signal at the end to display the digits properly. rather, just having a board with 2x 7segs (+resistors) it might display a noisy signal. am i wrong? pretty text book BCD to 7 seg decoder, nice write up post btw.

stupid question though: what are the "RRC" components (near the header) on the credit counter board? i can't find that part number anywhere. am i missing something obvious?

Click to expand...

I'll have to check it out when I get home, I haven't looked at it at all since I powered up.

On the RRC components, I think it's like a resistor pack/capacitor combination part. It's just used for noise reduction. Thankfully for us since that part is impossible to find, there's much better and easier ways to reduce noise on the PCB than some obscure component.

^two sets of bypass capacitors, schmitt trigger invertors+dflipflop, rrc filter? The FCC warning sticker on the cabinet is no joke!
They forgot to wrap the harness around a loop magnet and to use coax for the harness wires...

xhiltch said:

^two sets of bypass capacitors, schmitt trigger invertors+dflipflop, rrc filter? The FCC warning sticker on the cabinet is no joke!
They forgot to wrap the harness around a loop magnet and to use coax for the harness wires...

Click to expand...

Haha yeah, then the wire harness that comes with it is like 3 ft long or something, isn't it?

Fixed, see technical fix up above if you're interested. SNK original on left, reproduction on right

Great work, Jakeus. Unfortunately, there's no easy way to connect that MV-LED2 to a MV1C since it has no interface for telling the credit counter how many credits still left. Am I right? After finishing some hardcore consolization projects I'm working on, I'll try to figure out how the MV1 credit interface works and maybe will try to reproduce it in some way. Again without the schematics it will turn a nightmare, besides some custom chip (neo-fo) is involved. It would be also amazing to develop a Memory Card interface for that board, but it seems unrealistic by now. Again, a custom chip (neo-eo) is involved. The pinouts are on the web mentioned above. I would love to develop that, but my knowledge on digital buses is not that high to reproduce that chips, unfortunately.
I've seen some interest from some forum members on a project like that. IIRC Razoola confirmed time ago it could be done.

Coming back to the MV1C schematics, it seems that the inner PCB layers are only for +5v and GND, but don't take it for sure yet.

Just a small update. I have ordered a fixed prototype of "MV-LED", not to be confused with "MV-LED2". This is the one for the 4-slot. I should have it around the end of May, so I will focus on other side projects till then

works perfect!

It would be great if it could be added to a MV1C board. I know an interface chip would be needed, but dreaming is free.

Hi,
I was thinking at the same things.
If we know wich adress is used to write credit, a little interface to MCU could be done to display credit on MV1C. But maybe Universe Bios will be mandatory as original BIOS don't seems to support this feature.
Maybe someone know this address ? I will be pleased to try ! I have got some spares display !
Bye

Hi'
I'm replying to myself.
I have looked furthermore in Neo geo dev wikii and find an interesting page :

http://neogeodev.wikkii.com/wiki/Memory_mapped_registers

It looks that the adresses are $380030 and $380040, first one is a latch, second one is called data. I think you put data in second one's and select wich display with first one ?
Any dev here ?

Bye

Thanks, aje_fr for the info. Any hardcore tech watching around here that could help the cause?

Anyone got a complete MV1C Work Ram and Backup ram pinout?

Xian Xi said:

Anyone got a complete MV1C Work Ram and Backup ram pinout?

Click to expand...

I'm working on it but is not complete yet.

According to http://wiki.neogeodev.org/index.php?title=NEO-F0 it seems that NEO-F0 controls the credit LEDs. Could this chip be replicated in some way or is a complete custom built?

My goal is to connect a LED credit board (hand made) to a MV1c or similar small board.

Sorry for bumping an old thread, but where did the diagram in the first post go? :-/

Ok I found it :-) http://www.jamma-nation-x.com/jammax/images/tuts/mv1c-bios-full-pinout.jpg

LOL, thanks Xian for backing it up. Maybe I incidentally removed it from my ftp