In short, I found that in addition to S-VHS, the multiout also supports RGB and sync. I also got the controller pinouts and protocol, which opens up some interesting possibilities. One could rather easily construct a "macro recorder" that records your exact button presses for a game sequence and allows you to play them back. They will be time-accurate by definition of the protocol, and depending on how random the game plays, you should be able to replay those sequences that get boring, and then take over control when you want.
If all of this is already well known, then sorry for the waste of net bandwidth...
1 3 5 7 9 11
| | | | | |
| | | _ | | |
--------------------/ \--------------------
/ \
| |
| |
\ /
-------------------------------------------
| | | | | |
| | | | | |
2 4 6 8 10 12
Pin Description
=== ===========
1 Red analog video out (1v DC offset, 1vpp video into 75 ohms)
2 Green analog video out (1v DC offset, 1vpp video into 75 ohms)
3 Composite H/V sync out (1vpp into 75 ohms)
4 Blue analog video out (1v DC offset, 1vpp video into 75 ohms)
5 Ground
6 Ground
7 Y (luminance) signal for S-VHS (1vpp into 75 ohms)
8 C (chroma) signal for S-VHS (1vpp into 75 ohms)
9 NTSC composite video signal (1vpp into 75 ohms)
10 +5v (Could be just a high logic signal)
11 Left channel audio out
12 Right channel audio out
Additional Notes:As seen above, the SNES does have RGB capability. I was able to get a stable raster on my NEC MultiSync "classic" using the RGB and sync pins. However, the video levels are not RS-170 compatible. The DC offset needs to be filtered out with some large capacitors and the peak-to-peak video amplitude may need to be reduced to 0.7v by using a lower load impedance than 75 ohms. The Y/C (S-VHS) signals *appear* to be directly usable, but tests cannot be made until I find the pinouts for the S-VHS connector on my TV.
----------------------------- ---------------------
| | \
| (1) (2) (3) (4) | (5) (6) (7) |
| | /
----------------------------- ---------------------
Pin Description Color of wire in cable
=== =========== ======================
1 +5v White
2 Data clock Yellow
3 Data latch Orange
4 Serial data Red
5 ? no wire
6 ? no wire
7 Ground Brown
Additional notes:Pins 5 and 6 show a DC voltage of 5v on a DMM. I forgot to look at them on a scope so there may pulses too. However, they don't connect to anything at present.
The controllers have a small circuit board with 2 surface mount 14-pin ICs, marked by Nintendo as IC-A and IC-B. Although rubber domes are used to provide the tactile response of the buttons, they are not capacitive technology as originally thought. Instead they use what appears to be carbon impregnated rubber on the underside which makes a resistive path (200 ohms) across 2 carbon coated PCB pads when depressed.
Each button on the controller is assigned a specific id which corresponds to the clock cycle during which that button's state will be reported. The table in section 4.0 lists the ids for all buttons. Note that multiple buttons may be depressed at any given moment. Also note that a logic "high" on the serial data line means the button is NOT depressed.
At the end of the 16 cycle sequence, the serial data line is driven low until the next data latch pulse. The only slight deviation from this protocol is apparent in the first clock cycle. Because the clock is normally high, the first transition it makes after latch signal is a high-to-low transition. Since data for the first button (B in this case) will be latched on this transition, it's data must actually be driven earlier. The SNES controllers drive data for the first button at the falling edge of latch. Data for all other buttons is driven at the rising edge of clock. Hopefully the following timing diagram will serve to illustrate this. Only 4 of the 16 clock cycles are shown for brevity.
|<------------16.67ms------------>|
12us
-->| |<--
--- ---
| | | |
Data Latch --- -----------------/ /---------- --------...
Data Clock ---------- - - - -/ /---------------- - ...
| | | | | | | | | | | |
- - - - - -
1 2 3 4 1 2
Serial Data ---- --- ----/ / ---
| | | | | |
(Buttons B --- --- --- ----------
& Select norm B SEL norm
pressed). low low
12us
-->| |<--
Clock Cycle Button Reported
=========== ===============
1 B
2 Y
3 Select
4 Start
5 Up on joypad
6 Down on joypad
7 Left on joypad
8 Right on joypad
9 A
10 X
11 L
12 R
13 none (always high)
14 none (always high)
15 none (always high)
16 none (always high)
Additional notes: Clock cycles 13-16 are essentially unused. It would be interesting to see how the SNES responds if we drive low button data during these cycles. Nintendo may use these for future controllers with more capabilities.
(From the Editor)
NOTE: S-VHS is not means to mean Super-VHS. It stands for Super-Video (connector and output)
#### Additional Info (From Kevin Horton)
OK, the SNES uses the 65816 processor, which is basically a 16-bit version of the 6502. It runs at 3.579545 MHz (color-burst), and has an 8-bit data bus. It can address up to 16MB.
The carts are nothing more than ROM. To tell you how much data is one, take the number of 'MegaBits' and divide by 8 to get megabytes. That's how much data is really in the carts. So, an 8-mbit cart really is only 1 megabyte.