User talk:Jeffythedragonslayer

Four player adapters - signature byte

When talking about the four player adapters (Hori 4 Players Adapter, Four Score, or Satellite), the "signature byte" means: after you read 8 bits for controller 1 or 2, then read 8 more bits for controller 3 or 4, you read 8 more bits and make sure they match a known pattern. If those last 8 bits match the known pattern, that confirms the four player adapter is connected.

 Hori 4 Players Adapter
                                                                   |--signature--|
   Reads from $4016 bit 1: ¹A,B,SE,ST,U,D,L,R, ³A,B,SE,ST,U,D,L,R, 0,0,1,0,0,0,0,0
   Reads from $4017 bit 1: ²A,B,SE,ST,U,D,L,R, ⁴A,B,SE,ST,U,D,L,R, 0,0,0,1,0,0,0,0
 
 Four Score (and Satellite?)
                                                                   |--signature--|
   Reads from $4016 bit 0: ¹A,B,SE,ST,U,D,L,R, ³A,B,SE,ST,U,D,L,R, 0,0,0,1,0,0,0,0
   Reads from $4017 bit 0: ²A,B,SE,ST,U,D,L,R, ⁴A,B,SE,ST,U,D,L,R, 0,0,1,0,0,0,0,0

--Bavi H (talk) 00:36, 21 February 2023 (UTC)