TurboGrafx-16 Controller

Controller Pinout

8-pin female DIN jack at the console.

1. +5VDC
2. /North or /I
3. /East or /II
4. /South or /Select
5. /West or /Run
6. Data Select
7. /OE
8. GND

The eight signals are fed into a 74157 (4-of-8 noninverting decoder/demultiplexer) within the pad. The 74157 splits the eight signals into two sets of four, and the Data Select line determines which set is output on pins 2 through 5.

	Data Select
Pin	High	Low
2	North	I
3	East	II
4	South	Select
5	West	Run

Naturally, if the /OE line isn't pulled low, the controller doesn't output anything.

TurboTap

The TurboTap reads five controllers, one at a time. Things start when the console sends a pulse on the /OE line, which resets a counter in the tap. Controller 1 is then read as usual. The transition of the Data Select line from low to high increments the counter, and pad 2 is enabled. This keeps going with each low-to-high transition of the Data Select line enabling the next controller in line.

                         ---                                      ---
               /OE      |   |                                    |   |
    (counter reset)  ---     ------------------------------------     ---


        Data Select  ------------    --    --    --    --    ------------
(counter increment)              |  |  |  |  |  |  |  |  |  |
                                  --    --    --    --    --
  Pad/data set read            1A 1B 2A 2B 3A 3B 4A 4B 5A 5B

After controller 5 is read, all the tap outputs are low until the next /OE pulse. This could be how the console detects the presence of the tap, since it's pretty much impossible to smush all four directions at once.

Jay Tilton
05/01/00