SCC+ partial pinout revealed

In an act of curiosity, the MSX user ant0niutti took the time and effort to find out the pinout of the Konami SCC+ soundchip that was used in Snatcher and SD-Snatcher. The information he gathered suggests there might be some more features to the actual SCC+ sound chip than the cartridges sporting the chip currently allow, as some pins of the SCC+ are not actually connected. Furthermore, 4 pins are connected to GND and there are 2 clock input pins. Last but not least, but more commonly known, only 2 of the 4 memory banks are actually in use.

Relevant link: SCC+ pinout on MSX Land

Comentarios (13)

Por NYYRIKKI

Enlighted (5606)

07-06-2011, 14:51

Link has typo

Por snout

Ascended (15186)

07-06-2011, 15:39

Untypofied!

Por RetroTechie

Paragon (1563)

08-06-2011, 18:42

Let's try to un-mystify things... For those different GND/+5V pins, there's several possibilities:

Separate GND / supply pins for digital and analog parts inside the IC. This is common for A<->D converters, maybe same goes for SCC+ IC. Notice the grey resistor-like part in the middle? Looks like a small coil to me, this would suggest a little more attention to power supply filtering (and thus make sense to have separate supply pins).
Maybe there's some additional chip-select(s), that isn't used & thus always enabled.
Maybe a pin has no connection to IC internally, but it was easier to route board layout 'through' that pin.

About those 2 clock inputs: from the listing I gather the DRAM's data lines must be connected to data lines on cartridge connector (if they weren't, SCC+ IC would need separate data pins for connecting to cartridgeslot, and to the DRAMs). This means DRAMs must follow CPU timing when reading or writing, and the CLOCK signal is often used to generate correctly timed control signals (RAS / CAS / OE / WE). Also a clock signal is needed for sound generation. But this clock must be fixed frequency, CPU clock can vary depending on system the IC is used in. So maybe SCC+ is prepared for use in systems where CPU clock is something different than fixed 3.58 MHz. Other possibility is another "not connected" pin, where board layout is routed through.

Lastly I'm missing some signals: cartridgeslot MREQ (for read/write purposes it's included in SLTSL, so it's possible that it's not connected), and WE of the DRAMs.

Should be possible to measure / figure out some of the above, but IMHO not worth the effort since these SCC+ carts are so rare anyway (and expensive, and not produced anymore).

Por alexito

Hero (642)

31-10-2019, 12:15

Someone here can share this info again because the link is broke. I already tried wayback machine but not luck. I'm a happy owner of 3 SCC-I cartridges with 64Kb/128Kb/256Kb.

Recently I have discovery the Audio output for mixing with the MSX Computer is different that a regular SCC Cartridge. I'll try to make a video to explain better that behavior with my JVC HC-95 recently modified with V9958 and others. but my idea is to enhance or update the regular SCC Cartridge Audio mixing hardware.

Help is very appreciated.

Happy MSX Modding.

Por tfh

Prophet (2466)

31-10-2019, 14:09

Is the pin lay-out of the SCC-I so much different compared to the normal SCC?
I did find a pin-out for the SCC:

Can't find it for the SCC-I I'm afraid....

Por Pentarou

Champion (290)

31-10-2019, 17:36

Archive.org managed to grab a copy of the text:

Pinagem do SCC+
    Não localizei em local algum da internet a pinagem do SCC+, então mapeei aonde estão ligados os pinos dele no cartucho do SD-Snatcher. O resultado segue abaixo.
    Caso alguém tenha mais informações a respeito, por favor entre em contato.


Pino
do
SCC+ | onde está ligado
----------------------------------
01 - GND (pino 43 do slot)
02 - GND (pino 43 do slot)
03 - GND (pino 43 do slot)
04 - A7 memórias (pino 10)
05 - A3 memórias (pino 11)
06 - A2 memórias (pino 12)
07 - A1 memórias (pino 13)
08 - A0 memórias (pino 14)
09 - A4 memórias (pino 08)
10 - A5 memórias (pino 07)
11 - A6 memórias (pino 06)
12 -
13 - OE memórias (pino 01)
14 -
15 -
16 - Pino 13 da ponte de resistores
17 - pino 12 da ponte de resistores
18 - pino 11 da ponte de resistores
19 - pino 10 da ponte de resistores
20 - pino 09 da ponte de resistores
21 - pino 08 da ponte de resistores
22 - pino 01 e 14 da ponte de resistores
23 - pino 07 da ponte de resistores
24 - pino 06 da ponte de resistores
25 - pino 05 da ponte de resistores
26 - pino 04 da ponte de resistores
27 - pino 03 da ponte de resistores
28 - DO1 memórias (pino 02) dos dois chips opostos ao conector de slot (*)
29 - DO2 memórias (pino 03) dos dois chips opostos ao conector de slot (*)
30 - DO3 memórias (pino 15) dos dois chips opostos ao conector de slot (*)
31 - DO4 memórias (pino 17) dos dois chips opostos ao conector de slot (*)
32 - GND (pino 43 do slot)
33 - DO4 memórias (pino 17) dos dois chips próximos ao conector de slot (*)
34 - DO3 memórias (pino 15) dos dois chips próximos ao conector de slot (*)
35 - Do2 memórias (pino 03) dos dois chips próximos ao conector de slot (*)
36 - DO1 memórias (pino 02) dos dois chips próximos ao conector de slot (*)
37 - A5 (pino 31 do slot)
38 - A4 (pino 32 do slot)
39 - A3 (pino 29 do slot)
40 - A2 (pino 30 do slot)
41 - A1 (pino 27 do slot)
42 - A0 (pino 28 do slot)
43 - A14 (pino 25 do slot)
44 - A13 (pino 26 do slot)
45 - A12 (pino 23 do slot)
46 - A8 (pino 24 do slot)
47 - A7 (pino 21 do slot)
48 - A6 (pino 22 do slot)
49 - A11 (pino 19 do slot)
50 - A10 (pino 20 do slot)
51 - A9 (pino 17 do slot)
52 - A15 (pino 18 do slot)
53 - /RESET (pino 15 do slot)
54 - /WR (pino 13 do slot)
55 - /RD (pino 14 do slot)
56 - /RFSH (pino 06 do slot)
57 - /SLTSL (pino 04 do slot)
58 - CAS memórias (pino 16 do primeiro e terceiro chips, os dois soldados na placa) (**)
59 - CAS memórias (pino 16 do segundo e quarto chips, os dois ausentes na placa) (**)
60 - RAS memórias (pino 5 dos 4 chips)
61 - SND_CLK-IN (pino 42 do slot) (***)
62 - CPU_CLK-IN (pino 42 do slot) (***)
63 - +5V (pino 47 do slot)
64 - +5V (pino 47 do slot)
-----------------------------------------------------------------------

(*) Apesar de existir local na placa para 4 chips de memória 4464, originalmente só existem 2 chips nela, o primeiro (mais próximo do conector de slot) e o terceiro.
(**) Considero como primeiro chip de memória o mais próximo do conector do slot.
(***) Thanks to Dhampird

Por gdx

Prophet (3817)

01-11-2019, 16:24

I put it in the wiki.
http://www.msx.org/wiki/Konami_SCC
http://www.msx.org/wiki/Konami_SCC-I

Por o.geerdink

Hero (567)

02-11-2019, 06:55

So, any hidden drum register found jet?

Por alexito

Hero (642)

02-11-2019, 10:50

@Pentarou: Thanks
@GDX: Just my humble contribution to the MSX community about how to mod the SCC-I from 64KB to 256KB RAM using 4 RAM chips from Hyundai (HY51C4256) and the pin 12 on SCC-I it need to be connected to A8 on HY51C456 (pin15)

https://drive.google.com/open?id=13Ip_o7YSrvA7Q5uGFQdHU3gUy1...
https://imgur.com/pZNREzK

maybe this can help you also:
https://drive.google.com/open?id=1aVd9Xx1Oylbmm2vciur3-LZxZl...
https://imgur.com/1jsFhXc

and this but not intented yet:
https://oshpark.com/shared_projects/u2ReIlKX

Now who of you guys will try to improve the mod reaching the 512KB RAM so Goonies can run on it. ;)

Por gdx

Prophet (3817)

02-11-2019, 10:46

Thanks, I added the pin 12 and fixed the 13 and 14.

Por sd_snatcher

Prophet (3367)

02-11-2019, 14:08

alexito wrote:

Nice finding! But shouldn't 4x 44256 DRAM chips give you 512KB of RAM? Do you have any idea why half of the memory capacity is being lost?

Maybe the one of the unknown pins 13 or 15 is used to configure the DRAM chip size? It's worth to try to use a 4K7 resistor to pull them up or down to see if it changes anything.

Por sd_snatcher

Prophet (3367)

02-11-2019, 14:12

Quote:

and this but not intented yet:
https://oshpark.com/shared_projects/u2ReIlKX

That adapter was designed by Belavenuto and me. :)

But, IMHO, for this cartridge a custom single PCB adapter would be a better solution, given the scarce space available.

Por gdx

Prophet (3817)

02-11-2019, 14:47

sd_snatcher wrote:

Maybe the one of the unknown pins 13 or 15 is used to configure the DRAM chip size?

Finally, the pin 13 is used, it's well /OE. Pin 15 is probably TEST or Fref.

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