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[edit] Compatibility

"snes-d0 here should be pulled high (will read as 0). This will screw up multitap detection in any game that follows Nintendo's recommended programming procedures"

Are you sure there's a problem with that? Nintendo has released "MultiPlayer5" schematic & source code (found in book2.pdf). The schematic doesn't do anything special with 4017.bit0. And the source code only checks 4016.bit1 (for rejecting multtap on connector 1) and 4017.bit1 (for detecting it on desired connector), but it doesn't check 4017.bit0.
Did Nintendo release any other docs/drivers that do check that bit? Or are there any games that do so? nocash -- 23:26, 2 June 2011 (UTC)

[edit] Internal State

"It was found to be a Texas Instruments 16L8 PAL. This means the logic is completely combinatorial and thus cannot have an internal state"

But couldn't it use the logic gates to create a flipflop? For example, with two NOR gates:
    SET ___ _____
           | NOR \__
         __|_____/  |____ /OUT
        |____  _____|
        |__ _____   |____ OUT
           | NOR \__|
    CLR ___|_____/
Like setting the flipflop upon "strobe" signal (aka "latch" signal), and clearing it via "io" signal. At that point, I would change "io" direction from input to output, and send the data for player 6 through that line. Though, according to your info, "io" is wired to an input-only pin on the PAL chip, and so the direction couldn't be changed. nocash -- 23:26, 2 June 2011 (UTC)

[edit] Pin-Outs

"notice nothing depends on B0 (the p6 data line)"

Hmmmmm, player 6 input is wired to "B0" (PAL Pin 12)? According to datasheets from Texas Instruments and Fairchild, Pin 12 and 19 are outputs (only pin 13-18 are i/o). That'd really explain why it doesn't work :-) nocash -- 23:26, 2 June 2011 (UTC)

[edit] TribalTap6 Schematic

Just tried to combine your descriptions into a schematic. If I didn't got it wrong, it should look as below? nocash -- 23:26, 2 June 2011 (UTC)

                           _____   _____
                          |     \_/     |
 VCC--[RP]-------CLK---> 1|IN0       VCC|20 <---VCC
 VCC--[RP]--------IO---> 2|IN1 16L8 OUT7|19 --->IN0    (out-only)
 VCC--[RP]-----IN0'A---> 3|IN2 PAL  I/O6|18 --->IN1
 VCC--[RP]-----IN1'A---> 4|IN3      I/O5|17 --->STB'A
 VCC--[RP]---/MODE6P---> 5|IN4      I/O4|16 --->IO'A
 VCC--[RP]-----IN0'B---> 6|IN5      I/O3|15 --->CLK'B
 VCC--[RP]---/MODE2P---> 7|IN6      I/O2|14 --->CLK'CDE
 VCC--[RP]-----IN0'D---> 8|IN7      I/O1|13 --->STB'BCDE
 VCC--[RP]-----IN0'C---> 9|IN8      OUT0|12 <---IN0'E  (out-only???)
                 GND -->10|GND       IN9|11 <---/STB----[R]---VCC
       __________             _______               _______
      |3-position|           | S9013 |             | S9013 |        +-[R]-STB
      |switch  2P|--/MODE2P  |      E|-->VCC'BCDE  |      E|---GND  |
 GND--|        5P|--NC       | NPN  B|<--/MODE2P   | NPN  B|<-------+
      |        6P|--/MODE6P  |      C|---SNES.VCC  |      C|-->/STB |
      |__________|           |_______|             |_______|        +-[R]-GND
 |   (Female)(.............Male........................)|    ???--|LED>--???
 |Pin SNES   PORT2   PORT3    PORT4    PORT5    PORT6   |
 |1   VCC    VCC     VCC'BCDE VCC'BCDE VCC'BCDE VCC'BCDE|    further resistors
 |2   CLK    CLK     CLK'B    CLK'CDE  CLK'CDE  CLK'CDE |    ???
 |4   IN0    IN0'A   IN0'B    IN0'C    IN0'D    IN0'E   |    (not installed)
 |5   IN1    (IN1'A) -        -        -        -       |    diodes ???
 |6   IO     (IO'A)  -        -        -        -       |
 |7   GND    GND     GND      GND      GND      GND     |
    Note: The PCB has wires to all 7 pins of PORT2,
    but the installed connector has only 5 pins, so,
    in practice, IN1'A and IO'A are not connected.

[edit] Tests

(From Iuri Guilherme ipv4 #1 ipv4 #2)

I have tested in a SNES three tribal taps with the only game that support two multitaps attached to the console (N-Warp Daisakusen, a homebrew game and so far the only game that allows more than 5 players - 8 can play).

Tribal taps were previously tested with original Bomberman carts for Super Famicom and the three were good.

Tests were made in SNS-101.

Controllers used were 1X Konami Command Controller for Super Famicom, 3X SNES Official Controller, 3X Players Generic SNES Controller, 1X Generic SNES Controller.

[edit] First test (8 player support):

First tribal tap plugged in SNES controller port 1; Second tribal tap plugged in SNES controller port 2; Four controllers were plugged in each tribal tap (ports 2, 3, 4 and 5 were used - no #6 ports were used); Tribal taps were set into 5 player mode; Console turned on; Game image was loaded into a Super UFO Pro 8 DRAM and loaded; Game worked normally; I was able to play with 8 players and every button worked well.

Conclusion: SNES does allow 8 players. Two tribal taps works for 8 players.

[edit] Second test (#6 port test):

Console was turned off; The controller that was plugged on #5 port of the second tribal tap was removed and attached to the #6 port of the first tribal tap; Tribal taps set on 6 player switch; Console turned on and game loaded again like in first test; Game allowed 7 players; The first time i pressed the controller attached to port #6 (on the player select screen) it did nothing that I could notice. The second time (while the game was actually running) for a short time it made the player 4 move, then it stopped working at all.

Conclusion: Tribal tap #6 port is really attached to ports 3 and 4 and does not work. But perhaps someone can mod it and make it work, however there are no current 10 player game to test it, and making it just to allow 6 players with a single tap would not make any difference. AND it seems that SNES doesn't have support for more than 8 controllers either (theoretically twin taps could be attached to each multitap port making an ultimate cap of 16 controllers, but that should not work as expected).

[edit] Third test (nesting tribal taps):

Konami Command Controller was plugged in SNES controller port 1; Tribal tap one was plugged in SNES controller port 2 and set for 5 players; Tribal tap two was plugged in Tribal tap one #2 port and set for 5 players; Tribal tap three was plugged in Tribal tap two #2 port and set for 5 players; One controller was plugged in Tribal tap three #2 port; Several controllers were plugged in all tribal taps ports 3, 4 and 5; Game N-Warp was loaded like in the other tests; Game allowed 5 players. Working controllers were the one plugged in the first port, the ones plugged in tribal tap one 3, 4 and 5 ports, and the controller plugged to the #2 port of the tribal tap three. Controllers attached to nested tribal taps ports 3, 4 and 5 didn't worked at all;

Third test variations:

I have tried to nest the tribal taps in different ports, the result is the same (nested tribal taps only allow the #2 port). Except for plugging tribal taps or controllers to the #6 port of any tribal tap which never works.

Conclusion: Nesting tribal taps works for using it in two player mode, which is stupid because you get the same result using only one tap (the nested tribal taps allow only the #2 port, any controllers plugged in other ports won't work).

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