Gunfright: Routine at 53547

53547: Read Kempston Joystick

Used by the routine at ReadControls.

Reads a Kempston joystick from port 31.

Output
C	The controls

Read the joystick, and start with no controls.

ReadKempstonJoystick

53547

IN A,(31)

Read the joystick from port 31.

53549

LD C,0

Clear the controls.

Set bit 1 if the joystick is pushed right.

53551

BIT 0,A

Set bit 1 if the joystick is pushed right.

53553

JR Z,ReadKempstonJoystick_TestLeft

53555

SET 1,C

Set bit 0 if the joystick is pushed left.

ReadKempstonJoystick_TestLeft

53557

BIT 1,A

Set bit 0 if the joystick is pushed left.

53559

JR Z,ReadKempstonJoystick_TestDown

53561

SET 0,C

Set bit 4 if the joystick is pushed down.

ReadKempstonJoystick_TestDown

53563

BIT 2,A

Set bit 4 if the joystick is pushed down.

53565

JR Z,ReadKempstonJoystick_TestUp

53567

SET 4,C

Set bit 2 if the joystick is pushed up.

ReadKempstonJoystick_TestUp

53569

BIT 3,A

Set bit 2 if the joystick is pushed up.

53571

JR Z,ReadKempstonJoystick_TestFire

53573

SET 2,C

Set bit 3 if the fire button is pressed.

ReadKempstonJoystick_TestFire

53575

BIT 4,A

Set bit 3 if the fire button is pressed.

53577

JR Z,ReadKempstonJoystick_Finish

53579

SET 3,C

Jump to ReadControls_Rotate.

ReadKempstonJoystick_Finish

53581

JP ReadControls_Rotate

Jump to ReadControls_Rotate.

View the equivalent code in;