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===== Notes about the Altai Joystick Interface =====
The ALTAI interface connects to the Printer port which is also used when transferring data to the sound chip.
Sound corruption is therefore in most cases unavoidable.

Note all drivers use a common label list that is found here [[oric:hardware:generic_joystick_drivers]]

===== Hardware Notes =====
The Altai (Commonly mistaken for a PASE interface) was the most common joystick interface and supported in many games.
However it affected sound badly as it acted directly on the Parralel port.

The Altai interface connected to the Centronics Parralel port.
  B7 Select Left Joystick(Though neither sockets were distinguishable)
  B6 Select Right Joystick
  B5 Fire(Inverted)
  B4 Up(Inverted)
  B3 Down(Inverted)
  B2 -
  B1 Right(Inverted)
  B0 Left(Inverted)
DDRA must be set to 11000000 whilst reading Joystick.
Please note that setting both top bits does not permit both joystick ports to be read at the same time. I have now tested this and it doesn't work :(

===== Original Driver =====
The First Driver is the code taken directly out of the leaflet that came with the ALTAI interface, disassembled, corrected and optimised.


         LDA #%11000000
         STA via_ddra
         lda #%10000000
         STA via_porta
         LDA via_porta
         STA joy_Left
         LDA #%01000000
         STA via_porta
         LDA via_porta
         STA joy_Right
         LDA #%11111111
         STA via_ddra
         RTS

Each joystick movements will produce the following codes.
^Left Joystick Movement^Value(Decimal)^Value(Binary)^
| |191|10111111|
|Up|175|10101111|
|Up Right|173|10101101|
|Right|189|10111101|
|Right Down|181|10110101|
|Down|183|10110111|
|Down Left|182|10110110|
|Left|190|10111110|
|Up Left|174|10101110|
|Fire|159|10011111|

^Right Joystick Movement^Value(Decimal)^Value(Binary)^
| |127|01111111|
|Up|111|01101111|
|Up Right|109|01101101|
|Right|125|01111101|
|Right Down|117|01110101|
|Down|119|01110111|
|Down Left|118|01110110|
|Left|126|01111110|
|Up Left|110|01101110|
|Fire|95|01011111|

As the Bit pattern suggests when a joystick is moved, its corresponding bit is reset.
Also Bit7 selects the Left joystick and Bit6 selects the right joystick.

===== Generic Joystick Driver for the ALTAI Interface =====
The following code provides a standard output for detection of joystick movements in your own code.
Whilst the corresponding bits remain the same they are inverted to conform to the Generic Format.

       GenericReadAltai
         LDA #%11000000
         STA via_ddra
         lda #%10000000
         STA via_porta
         LDA via_porta
         AND #%00111111
         EOR #%00111111
         STA joy_Left
         LDA #%01000000
         STA via_porta
         LDA via_porta
         AND #%00111111
         EOR #%00111111
         STA joy_Right
         LDA #%11111111
         STA via_ddra
         RTS

This provides the following bits to joystick movements.
^Bit^Value^Joystick Movement^
|0|1|Left|
|1|2|Right|
|2|4| |
|3|8|Down|
|4|16|Up|
|5|32|Fire|
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