Routines
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B103: Controls: Cursor Joystick
Used by the routine at HandlerControls.
Reads a Cursor joystick, which is mapped onto the keys "5" to "8" and "0".
Output
C Joystick controls
Initialise the controls as "none" in C.
ReadCursorJoystick B103 LD C,$00 Clear the controls in C.
The cursor keys are covered by different ports.
HandleCursorJoystick_Port_F7 B105 LD A,$F7 Read from the keyboard;
Port Number Bit
0 1 2 3 4
F7 1 2 3 4 5
B107 OUT ($FD),A
B109 IN A,($FE)
Check joystick "LEFT".
ReadCursorJoystick_Left B10B BIT 4,A Jump to HandleCursorJoystick_Port_EF if "LEFT" (key "5") is not being pressed.
B10D JR NZ,HandleCursorJoystick_Port_EF
B10F SET 0,C Set the "LEFT" bit (bit 0) of the controls in C.
Handle the other port.
HandleCursorJoystick_Port_EF B111 LD A,$EF Read from the keyboard;
Port Number Bit
0 1 2 3 4
EF 0 9 8 7 6
B113 OUT ($FD),A
B115 IN A,($FE)
Check joystick "DOWN".
ReadCursorJoystick_Down B117 BIT 4,A Jump to ReadCursorJoystick_Up if "DOWN" (key "6") is not being pressed.
B119 JR NZ,ReadCursorJoystick_Up
B11B SET 3,C Set the "DOWN" bit (bit 3) of the controls in C.
Check joystick "UP".
ReadCursorJoystick_Up B11D BIT 3,A Jump to ReadCursorJoystick_Right if "UP" (key "7") is not being pressed.
B11F JR NZ,ReadCursorJoystick_Right
B121 SET 2,C Set the "UP" bit (bit 2) of the controls in C.
Check joystick "RIGHT".
ReadCursorJoystick_Right B123 BIT 2,A Jump to ReadCursorJoystick_Fire if "RIGHT" (key "8") is not being pressed.
B125 JR NZ,ReadCursorJoystick_Fire
B127 SET 1,C Set the "RIGHT" bit (bit 1) of the controls in C.
Check joystick "FIRE".
ReadCursorJoystick_Fire B129 BIT 0,A Return if "FIRE" (key "0") is not being pressed.
B12B RET NZ
B12C SET 4,C Set the "FIRE" bit (bit 4) of the controls in C.
B12E RET Return.
View the equivalent code in;
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