Routines
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D150: Read Cursor Joystick
Used by the routine at ReadControls.
Reads a cursor joystick. 5 is left, 8 is right, 7 is up, 6 is down and 0 is fire.
Output
C The controls
Start with no controls, and read 5 for left.
ReadCursorJoystick D150 LD C,$00 Clear the controls.
D152 LD A,$F7 Read from the keyboard;
Port Number Bit
0 1 2 3 4
F7 1 2 3 4 5
D154 CALL ReadKeyboardPort
D157 BIT 4,A Set bit 0 if 5 is pressed.
D159 JR Z,ReadCursorJoystick_SecondRow
D15B SET 0,C
Read 0, 7, 8 and 6.
ReadCursorJoystick_SecondRow D15D LD A,$EF Read from the keyboard;
Port Number Bit
0 1 2 3 4
EF 0 9 8 7 6
D15F CALL ReadKeyboardPort
D162 BIT 0,A Set bit 3 if 0 is pressed.
D164 JR Z,ReadCursorJoystick_TestUp
D166 SET 3,C
Set bit 2 if 7 is pressed.
ReadCursorJoystick_TestUp D168 BIT 3,A Set bit 2 if 7 is pressed.
D16A JR Z,ReadCursorJoystick_TestRight
D16C SET 2,C
Set bit 1 if 8 is pressed.
ReadCursorJoystick_TestRight D16E BIT 2,A Set bit 1 if 8 is pressed.
D170 JR Z,ReadCursorJoystick_TestDown
D172 SET 1,C
Set bit 4 if 6 is pressed, and jump to ReadControls_Rotate.
ReadCursorJoystick_TestDown D174 BIT 4,A Jump to ReadControls_Rotate if 6 is not pressed.
D176 JR Z,ReadControls_Rotate
D178 SET 4,C Set bit 4, and jump to ReadControls_Rotate.
D17A JR ReadControls_Rotate
View the equivalent code in;
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