Gunfright: Routine at D12B

D12B: Read Kempston Joystick

Used by the routine at ReadControls.

Reads a Kempston joystick from port 1F.

Output
C	The controls

Read the joystick, and start with no controls.

ReadKempstonJoystick

D12B

IN A,($1F)

Read the joystick from port 1F.

D12D

LD C,$00

Clear the controls.

Set bit 1 if the joystick is pushed right.

D12F

BIT 0,A

Set bit 1 if the joystick is pushed right.

D131

JR Z,ReadKempstonJoystick_TestLeft

D133

SET 1,C

Set bit 0 if the joystick is pushed left.

ReadKempstonJoystick_TestLeft

D135

BIT 1,A

Set bit 0 if the joystick is pushed left.

D137

JR Z,ReadKempstonJoystick_TestDown

D139

SET 0,C

Set bit 4 if the joystick is pushed down.

ReadKempstonJoystick_TestDown

D13B

BIT 2,A

Set bit 4 if the joystick is pushed down.

D13D

JR Z,ReadKempstonJoystick_TestUp

D13F

SET 4,C

Set bit 2 if the joystick is pushed up.

ReadKempstonJoystick_TestUp

D141

BIT 3,A

Set bit 2 if the joystick is pushed up.

D143

JR Z,ReadKempstonJoystick_TestFire

D145

SET 2,C

Set bit 3 if the fire button is pressed.

ReadKempstonJoystick_TestFire

D147

BIT 4,A

Set bit 3 if the fire button is pressed.

D149

JR Z,ReadKempstonJoystick_Finish

D14B

SET 3,C

Jump to ReadControls_Rotate.

ReadKempstonJoystick_Finish

D14D

JP ReadControls_Rotate

Jump to ReadControls_Rotate.

View the equivalent code in;