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:-http://www.datasheetarchive.com/pdf-datasheets/Datasheets-27/DSA-525846.html
(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:-http://www.datasheetarchive.com/pdf-datasheets/Datasheets-309/70953.html
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:-http://www.megaupload.com/?d=500F3QW3
(Sorry I dont really use filesharing sites, so I dont know if theres better ones available than megaupload)
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):-http://www.megaupload.com/?d=D1DOBTAS
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