User talk:Jeffythedragonslayer
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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
