SNES & N64 Video Encoder Information/Datasheets

Started by Link83, January 11, 2009, 12:53:43 AM

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Link83

January 11, 2009, 12:53:43 AM Last Edit: July 08, 2020, 11:48:53 AM by Link83 Reason: Fixed links
Apologies in advance for the length of this post! Im not sure if this is the right forum to be posting this in, but it was the only one it seemed to fit.

  I have been on abit of a quest as of late to find out as much as I can about the Video Encoders used in the SNES and N64 consoles - especially datasheets if possible (I was hoping to find some for the D/A convertors aswell, but since these are obviously ASIC's I dont think we will ever get those) and I just want to share the information that I have found  :)

  As im sure you know they are all made by ROHM, but due to non-disclosure agreements with Nintendo they dont give out the datasheets for the specific chip numbers, so what I thought id try to do was find out what encoders ROHM made at the time that were 'similar' to the ones used in the SNES and N64. I used a combination of the internet archive and Hong Kong chip supply lists to figure out which ones would be good candidates.

These are the original chips I was hoping to find out more about:-

BA6592F SOP24 chip used in the first produced NTSC SNES consoles. Converts RGB into S-Video and Composite.
S-ENC SOP24 chip used in early SNES consoles. Converts RGB into S-Video and Composite. This is likely either a rebranded BA6592F, or it might be a BA6594F. I originally thought that it might be a BA6593F based on the numbering scheme, but a quick google search doesnt reveal any chip  suppliers with stock for that code so it likely does not exist.
S-ENC B BA6594AF SOP24 chip used in mid-produced SNES consoles. Converts RGB into S-Video and Composite and appears to have the same pinout as the BA6592F/S-ENC, so is likely a slightly improved version.

S-RGB BA6595F SOP24 chip used in later SNES consoles. Converts RGB into S-Video and Composite and also amplifies and outputs analog RGB.
S-RGB A BA6596F SOP24 chip used in the last produced SNES consoles, the SNES2/SFCJr and an early French N64. Converts RGB into S-Video and Composite and also amplifies and outputs analog RGB. Appears to have the same pinout as the BA6595F, so is likely a slightly improved version.

ENC-NUS BA7242F SOP14 chip used in early NTSC N64 consoles. Converts RGB into S-Video and Composite.

After the ENC-NUS Nintendo started using combined DAC/video encoders which are all ROHM custom ASIC parts (DENC-NUS, AVDC-NUS, MAV-NUS, etc)

I soon discovered one that was a perfect match for the ENC-NUS chip, its the BA7242F and heres the datasheet:-
https://www.dropbox.com/s/ww9gagimbzn6td4/BA7242F%20ENC-NUS.pdf?dl=0
(The first page mentions that it also outputs analog RGB, but I believe this is an error as the rest of the document makes no mention of this)

Pretty pleased with having discovered the ENC-NUS datasheet I next started looking for the BA6595F/BA6596F. I had already made a pinout of the BA6596F by following its traces, heres a pic I made (I used Viletims N64 DAC pictures as a template, hope he doesnt mind):-


I didnt manage to find an exact match, but the BA7232FS SOP20 encoder seems to be pretty close, and is perhaps its direct successor. Heres the datasheet:-
https://www.dropbox.com/s/8zyq692l0sunxo4/BA7232FS%20Like%20S-RGB.pdf?dl=0

The main differences are the unused pins between the RGB inputs and outputs have been removed (BA6596F Pins 2, 4, 21, 23) so its now a SOP20 package - in effect the BA7232FS seems like a slightly 'top squashed' version of the BA6595F/BA6596F. There is also one less ground connection (BA6596F Pin 16) and the datasheet mentions that Pin 16 on the BA7232FS is C-Sync out, which might mean that the BA6596F supports C-Sync on Pin 18 but I haven't tested this, and this pin is not connected/used on the late model SNES consoles that use this encoder.

Last was the BA6592F, with this being the oldest chip I guessed this would be the one I would have the most difficulty finding. The internet archive doesnt go back far enough so I looked at Hong Kong chip supply lists and found out there was a BA6591AF which came in a SOP24 package. I looked around but couldnt find a datasheet for this anywhere, so I decided to email ROHM and see if they could help. The person who replied was very helpful and gave me this datasheet:-
https://www.dropbox.com/s/x7zp7sbcpwwuayu/BA6591AF.pdf?dl=0

It almost seems like a perfect match for the BA6592F from what I have seen of the reverse engineered SNES schematics.

I was already pretty pleased with the info I had found so far but as a final last 'last ditch' attempt I thought id ask my ROHM contact if they had the datasheet for the BA6592F, BA6595F or BA6596F -  I was expecting to get no reply, or one stating that they cannot disclose them. They didnt have one for the BA6595F or BA6596F, but to my great surprise they gave me the datasheet for the BA6592F! (Although they only have it available in Japanese, its almost identical to the datasheet layout used in the BA6951AF which is in English so you can easily work it out):-
https://www.dropbox.com/s/mcawkcal6s1oxge/BA6592F.pdf?dl=0

I was very surprised to get it - I dont know if people just havent requested it before, or if they accidentally sent it to me. In any case I was pretty pleased :) The only thing I ask is that people dont go asking ROHM for even more info about this chip, as if it was a mistake the person who sent the datasheet to me could get in trouble, and I really dont want that to happen. (I realise im probably over-worrying here considering it is an obsolete almost 20 year old chip!)

Anyway, I think I have taken this 'detective work' as far as I can. I hope you find the resulting information useful, and hopefully it can be put to good use by some of you  ;)

Please let me know what you think  ;D

juanesmh

this information  is awesome!!
It was very helpful for me.
But, the  link to BA6592F datasheet doesn't work.  Could you please upload again?
Thanks a lot!!    :)

RGB32E

Have any of you tried a RGB bypass mod on a SNES yet?  Oh wait... I guess I should just go and try myself! ;)

keropi

Quote from: RGB32E on July 06, 2010, 04:59:48 PM
Have any of you tried a RGB bypass mod on a SNES yet?  Oh wait... I guess I should just go and try myself! ;)

what will you gain? quality?  ???
As far as I've seen from my SNES the rgb quality is very good  :)

RGB32E

Quote from: keropi on July 06, 2010, 06:15:41 PM
Quote from: RGB32E on July 06, 2010, 04:59:48 PM
Have any of you tried a RGB bypass mod on a SNES yet?  Oh wait... I guess I should just go and try myself! ;)

what will you gain? quality?  ???
As far as I've seen from my SNES the rgb quality is very good  :)

From my sampling, RGB quality varies from system to system.

Midori

Colours are good imo but the image is very soft and there is something wrong with the signal which produces a light vertical bar on some of my monitors, not serious but definitely flawed. If a bypass would redeem these two faults it would be awesome :-) But I'm too lazy to try myself so I'll wait på 32E.

Shadow_Zero

May 11, 2013, 07:48:10 AM #6 Last Edit: July 08, 2020, 07:01:56 PM by Shadow_Zero
Quote from: Link83 on January 11, 2009, 12:53:43 AMAnyway, I think I have taken this 'detective work' as far as I can. I hope you find the resulting information useful, and hopefully it can be put to good use by some of you  ;)

Please let me know what you think  ;D
You sir, are a hero! Can you sign my Legend of Zelda dvd-box!  ;D
(heck, I might even consider to let you sign my goldie NES carts :P )

EDIT:
@Link83: It's interesting to see @Scias didn't have as much luck requesting data sheets from Rohm in his 'PAL N64 RGB' topic (https://nfggames.com/forum2/index.php?topic=850.msg18084#msg18084 !)

niall

Any chance the megauploads can be uploaded somewhere else, can we host them here or can someone point me to them via PM?

Broox

Quote from: niall on April 08, 2014, 11:49:00 PM
Any chance the megauploads can be uploaded somewhere else, can we host them here or can someone point me to them via PM?

Can someone upload this to dropbox please?

Shadow_Zero

July 07, 2020, 08:36:19 AM #9 Last Edit: July 08, 2020, 07:04:59 PM by Shadow_Zero
Trying to pick up some SNES and N64 mod projects again (after like, 7 years... >_> ), I have been reading a lot into SNES and N64 video encoding these couple of days (feels like my head is spinning now XD ), and maybe this is not the proper topic for it, but I wanted to share some info I collected (at least handy for archiving purpose).

Some photos I still had from (PAL) SNES boards:
SNSP-CPU-02 (S-CPU, S-PPU1, S-PPU2, S-ENC):


SNSP-CPU-1CHIP-01 (S-CPUN, S-RGB):



SNSP-CPU-1CHIP-02 (S-CPUN, S-RGB):



And some info from various places of the forum:

viletim's schematics:
http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm#snes

SNSP-CPU-1CHIP-02 pics from SnoWglobE:
https://nfggames.com/forum2/index.php?topic=215.msg29273#msg29273
https://commons.wikimedia.org/wiki/SNSP-CPU-1CHIP-02

Link83 about S-RGB on SNES:
https://nfggames.com/forum2/index.php?topic=3083.msg23629#msg23629

Link83 researching 1CHIP SNES Video Components:
https://nfggames.com/forum2/index.php?topic=3636

DarthCloud's schematics of the 1995 SNS-CPU-RGB-02 NTSC SNES (with S-RGB):
https://nfggames.com/forum2/index.php?topic=3083.msg25892#msg25892


Link83 figuring out the FRA N64 (uses S-RGB) missing components:
https://nfggames.com/forum2/index.php?topic=3083.msg23441#msg23441
https://nfggames.com/forum2/index.php?topic=3083.msg23629#msg23629
https://nfggames.com/forum2/index.php?topic=3083.msg25880#msg25880
Quote from: undefinedI am beginning to think that the little circuit on this French N64 was only there in order to maintain 'backward compatabilty' with the French SNES Scart cable.

Simply put, the originally planned video components for this French N64 were designed to work only with PAL SNES video cables  (Which use 75ohm resistors to ground) Its not the layout the 'S-RGB A' chips datasheet would have recommended, its what Nintendo had to do to maintain backwards compatibility with PAL video cables.

The NTSC method would be preferrable since it is the 'correct' method, its the layout the 'S-RGB A' chip was actually designed for, and is likely exactly what would have been recommended in the datasheet. It also means you could use 'standard' RGB cables with 220uF capacitors on R, G, B.

Shadow_Zero

July 08, 2020, 09:39:22 AM #10 Last Edit: July 08, 2020, 09:51:09 AM by Shadow_Zero
Ok, looking to restore s-video on my NUS-001(FRA) N64's and a little bit in doubt which way to go.
The 'old' method was just wiring the pins with 75ohm resistors to the av-out. Later on we learned that officially it also needs 220uF cap for luma and 68 nF cap for chroma. I also found a RetroRGB guide (https://www.retrorgb.com/snesminisvideo.html) where they mention "The 220uf capacitor connects to luma and the 0.1uf capacitor connects to chroma".

How necessary are they? Any (possible) side effects of not including them, or using the wrong value?


Sources I have used:

http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm#snes
https://gamesx.com/wiki/doku.php?id=av:nintendomultiav
https://gamesx.com/wiki/doku.php?id=av:n64rgb-ntsc
https://gamesx.com/wiki/doku.php?id=av:snes2rgb
https://www.retrorgb.com/snesminisrgb.html
https://www.retrorgb.com/snesminisvideo.html
https://www.sega-16.com/forum/showthread.php?18292-How-to-mod-your-Super-Nintendo-Mini-Jr-model-2-for-S-video
https://forum.digitpress.com/forum/showthread.php?126959-SNES-Jr-S-Video
http://www.retrogaming.com.ar/forum/viewtopic.php?f=4&t=2652


Quote from: ApolloBoy on March 05, 2014, 06:22:16 PMSince your N64 uses the same encoder as the SNES mini and 1chip SNES, adding S-video should be a fairly easy process. As I've stated in the wiki, you can add 75 ohm resistors (or 100-150 ohm if you find the resulting image is too bright) to the chroma and luma pins of the encoder and that should do it. The 220 uF cap for luma and 100 nF cap for chroma are optional but it won't hurt to have them in.

Quote from: Link83 on July 07, 2020, 08:40:34 AMS-Video requires 75ohm resistors to ground plus a 220uF capacitor and a 68nF capacitor
https://nfggames.com/forum2/index.php?topic=3380
https://nfggames.com/forum2/index.php?topic=3203.msg22654#msg22654
https://nfggames.com/forum2/index.php?topic=3083.msg46391#msg46391