Interface Protocol of SEGA MegaDrive's 6 Button Controller

Interface Protocol of SEGA MegaDrive's 6-Button-Controller

     Source: https://applause.elfmimi.jp/md6bpad-e.html
     Author: Ein Terakawa, applause@@elfmimi.jp
Last Update: 24/10/2016

Pin Assign (D-SUB9P)

SignalName	Explanation (Direction)
1. D0	Data (Controller -> Mainframe)
2. D1	Data (Controller -> Mainframe)
3. D2	Data (Controller -> Mainframe)
4. D3	Data (Controller -> Mainframe)
5. +5V	PowerSupply (Supplied to Controller by Mainframe)
6. D4	Data (Controller -> Mainframe)
7. Sel	SelectSignal (Mainframe -> Controller)
8. GND	Ground
9. D5	Data (Controller -> Mainframe)

All signals are TTL compatible.

In Case of 3-Button-Controller

 Sel  D0 D1 D2 D3 D4 D5
 Low  UP DW LO LO A  ST
 High UP DW LF RG B  C

   # LO --- Always Low
   # UP --- Up of Cross Key
   # DW --- Down of Cross Key
   # LF --- Left of Cross Key
   # RG --- Right of Cross Key
   # A ---- Trigger Button A
   # B ---- Trigger Button B
   # C ---- Trigger Button C
   # ST --- Start Button
   ## Low -> Pressed , High -> Not Pressed

Data Aquisition Sequence of 6-Button-Controller

Sel   D0 D1 D2 D3 D4 D5
Low   UP DW LO LO A  ST
High  UP DW LF RG B  C
Low   UP DW LO LO A  ST
High  UP DW LF RG B  C   # If there is two up-edge in 1.1 milli seconds,
Low   LO LO LO LO A  ST  # D0 - D3 go Low as Sel goes Low.
High  Z  Y  X  MD HI HI  # Make Sel High and read D0 - D3.
Low   HI HI HI HI A  ST  # Check that D0 - D3 go High as Sel goes Low.
High  UP DW LF RG B  C   # Once this sequence take place
Low   UP DW LO LO A  ST  # sequence can't be started for 1.8 milli seconds
.                        # after the first up-edge of Sel.
.                        # Only Datas read in 1.6 milli seconds from the
.                        # first up-edge of Sel are reliable.

   # LO --- Always Low
   # HI --- Always High
   # UP --- Up of Cross Key
   # DW --- Down of Cross Key
   # LF --- Left of Cross Key
   # RG --- Right of Cross Key
   # A ---- Trigger Button A
   # B ---- Trigger Button B
   # C ---- Trigger Button C
   # X ---- Trigger Button X
   # Y ---- Trigger Button Y
   # Z ---- Trigger Button Z
   # ST --- Start Button
   # MD --- Mode Button
   ## Low -> Pressed , High -> Not Pressed

Time parameters were measured by using my PC's timer. It seems that the time is measured by discharging of a capacitor in a 6-Button-Controller. It may mean parameters differ one by one controller. Please choose values you think proper for parameters.

Ein Terakawa

applause@@elfmimi.jp