Routines
Prev: 37784 Up: Map Next: 37859
37822: Read Controls
Used by the routines at HandlerWizard, ControlPlayer, HandlerSerf and HandlerKnight.
Reads the controls that were chosen in GameOptions. A bit is reset when the control is used: bit 0 is right, bit 1 is left, bit 2 is down, bit 3 is up and bit 4 is fire. The keyboard uses W, Q, E, R and T, the cursor keys are read by ReadCursorKeys and otherwise the Kempston joystick is read.
Output
A The state of the controls
ReadControls 37822 LD A,(24064) Fetch the controls that were chosen from GameOptions.
37825 AND %00000110 Keep only bits 1-2.
37827 JR Z,ReadControls_Keyboard Jump to ReadControls_Keyboard if the keyboard is used.
37829 CP 4 Jump to ReadCursorKeys if the cursor keys are used.
37831 JR Z,ReadCursorKeys
37833 IN A,(31) Read the Kempston joystick.
37835 CPL Flip the bits, so that a reset bit is a control which is used.
37836 RET Return.
ReadControls_Keyboard 37837 LD A,251 Read from the keyboard;
Port Number Bit
0 1 2 3 4
251 Q W E R T
37839 OUT (253),A
37841 IN A,(254)
37843 LD C,A Keep the keys in C.
37844 RRA Rotate A right, to move W (right) to bit 0.
37845 AND %00000001 Keep only bit 0.
37847 LD E,A Keep right in E.
37848 LD A,C Fetch the keys.
37849 RLA Rotate A left, to move Q (left) to bit 1.
37850 AND %00000010 Keep only bit 1.
37852 OR E Combine left with right.
37853 LD E,A Keep right and left in E.
37854 LD A,C Fetch the keys.
37855 AND %00011100 Keep only bits 2-4 (E is down, R is up and T is fire).
37857 OR E Combine down, up and fire with right and left.
37858 RET Return.
View the equivalent code in;
Prev: 37784 Up: Map Next: 37859