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Starbyte 4-Player Adapter Specs v0.1                   last changes: 14.03.2012
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Released by Starbyte Software in 1990 for use with their game 
"Adidas Championship Tie Break." 

At the time sold separately under the name "Tie Break Adaptor".

Note: although the adapter uses the same idea as the Kingsoft and DXS/HIT 
      adapters, it is NOT compatible with them!

Schematics:
-----------

GND     1 ---------------+--- 8  JOY 3  GND
CNT1    4 ->-+           +--- 8  JOY 4  GND
CNT2    6 -<-+
SP2     7 ----------<-------- 6  JOY 3  BUTTON
PB0     C ----------<-------- 2  JOY 3  A1
PB1     D ----------<-------- 4  JOY 3  A3
PB2     E ----------<-------- 3  JOY 3  A2
PB3     F ----------<-------- 1  JOY 3  A0
PB4     H ----------<-------- 6  JOY 4  BUTTON
PB5     J ----------<-------- 2  JOY 4  A1
PB6     K ----------<-------- 4  JOY 4  A3
PB7     L ----------<-------- 3  JOY 4  A2
PA2     M ----------<-------- 1  JOY 4  A0

note: all GND pins at the userport (1, 12, A, N) should be connected to each
      other.

Example code (from "Tie Break"):
--------------------------------

; port 3
.C:abcc  AD 01 DD    LDA $DD01
.C:abcf  85 CE       STA $CE

; get bit 1 from cia2 port b bit 0
.C:abd1  A9 00       LDA #$00
.C:abd3  46 CE       LSR $CE
.C:abd5  B0 02       BCS $ABD9
.C:abd7  09 02       ORA #$02

; get bit 3 from cia2 port b bit 1
.C:abd9  46 CE       LSR $CE
.C:abdb  B0 02       BCS $ABDF
.C:abdd  09 08       ORA #$08

; get bit 2 from cia2 port b bit 2
.C:abdf  46 CE       LSR $CE
.C:abe1  B0 02       BCS $ABE5
.C:abe3  09 04       ORA #$04

; get bit 0 from cia2 port b bit 3
.C:abe5  46 CE       LSR $CE
.C:abe7  B0 02       BCS $ABEB
.C:abe9  09 01       ORA #$01

.C:abeb  85 CE       STA $CE

; get fire from cia2 synchronous serial (SP2)
.C:abed  AD 0C DD    LDA $DD0C
.C:abf0  C9 FF       CMP #$FF
.C:abf2  F0 06       BEQ $ABFA

.C:abf4  A5 CE       LDA $CE
.C:abf6  09 10       ORA #$10
.C:abf8  85 CE       STA $CE
.C:abfa

; port 4
.C:ac00  AD 01 DD    LDA $DD01
.C:ac03  85 CE       STA $CE

; get bit 2 from cia2 port b bit 7
.C:ac05  A9 00       LDA #$00
.C:ac07  06 CE       ASL $CE
.C:ac09  B0 02       BCS $AC0D
.C:ac0b  09 04       ORA #$04

; get bit 3 from cia2 port b bit 6
.C:ac0d  06 CE       ASL $CE
.C:ac0f  B0 02       BCS $AC13
.C:ac11  09 08       ORA #$08

; get bit 1 from cia2 port b bit 5
.C:ac13  06 CE       ASL $CE
.C:ac15  B0 02       BCS $AC19
.C:ac17  09 02       ORA #$02

; get bit 5 from cia2 port b bit 4
.C:ac19  06 CE       ASL $CE
.C:ac1b  B0 02       BCS $AC1F
.C:ac1d  09 10       ORA #$10

.C:ac1f  85 CE       STA $CE

; get bit 0 from cia2 port a bit 2
.C:ac21  AD 00 DD    LDA $DD00
.C:ac24  29 04       AND #$04
.C:ac26  D0 06       BNE $AC2E
.C:ac28  A5 CE       LDA $CE
.C:ac2a  09 01       ORA #$01
.C:ac2c  85 CE       STA $CE
.C:ac2e

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credits:
--------

reverse enginering, this document :            Groepaz/Hitmen (groepaz@gmx.net)