Alien 8: Routine at C954

C954: Read Kempston Joystick

Used by the routine at ReadControls.

Reads the controls from a Kempston joystick.

Output
C	The controls

Read the port and map each bit to a control.

ReadKempstonJoystick

C954

IN A,($1F)

Read port 1F.

C956

LD C,$00

Set C to 00.

C958

BIT 0,A

Set bit 1 of C if bit 0 of A is set.

C95A

JR Z,ReadKempstonJoystick_TestLeft

C95C

SET 1,C

ReadKempstonJoystick_TestLeft

C95E

BIT 1,A

Set bit 0 of C if bit 1 of A is set.

C960

JR Z,ReadKempstonJoystick_TestDown

C962

SET 0,C

ReadKempstonJoystick_TestDown

C964

BIT 2,A

Set bit 4 of C if bit 2 of A is set.

C966

JR Z,ReadKempstonJoystick_TestUp

C968

SET 4,C

ReadKempstonJoystick_TestUp

C96A

BIT 3,A

Set bit 2 of C if bit 3 of A is set.

C96C

JR Z,ReadKempstonJoystick_TestFire

C96E

SET 2,C

ReadKempstonJoystick_TestFire

C970

BIT 4,A

Set bit 3 of C if bit 4 of A is set.

C972

JR Z,ReadKempstonJoystick_Finish

C974

SET 3,C

ReadKempstonJoystick_Finish

C976

JP ReadControls_Finish

Jump to ReadControls_Finish.

View the equivalent code in;