Spellbound (48k): Routine at 37928

37928: Capture Kempston joystick input

Used by the routine at 37876.

Input
HL	23485 (store for currently active keyboard press / joystick action)

Output
A	Stored key-press (bits: 0=LEFT, 1=RIGHT, 2=UP, 3=DOWN, 4=FIRE)

37928

LD C,31

Load 31 (Kempston port number) into C

37930

IN A,(C)

Read byte from port 31 (i.e. read state of joystick)

37932

BIT 0,A

If joystick moved right...

37934

CALL NZ,38063

...store a RIGHT input from control device

37937

BIT 1,A

If joystick moved left...

37939

CALL NZ,38060

...store a LEFT input from control device

37942

BIT 2,A

If joystick moved down...

37944

CALL NZ,38069

...store a DOWN input from control device

37947

BIT 3,A

If joystick moved up...

37949

CALL NZ,38066

...store an UP input from control device

37952

BIT 4,A

If fire button pressed...

37954

CALL NZ,38072

...store a FIRE input from control device

37957

LD A,(HL)

Return stored joystick movement in A

37958

RET

Return