Routines
Prev: 24968 Up: Map Next: 25026
24972: Input: Left/ Right
Used by the routine at 28210.
Check if this should be read from the Kempston joystick instead?
ReadInputLR 24972 LD A,(24126) If GameOptions indicates the control method is via the Kempston joystick then jump to ReadKempstonJoystick.
24975 BIT 1,A
24977 JR NZ,ReadKempstonJoystick
Check for "Left" and "Right" button inputs for port 254.
24979 LD A,254 Read from the keyboard;
Port Number Bit
0 1 2 3 4
$FE SHIFT Z X C V
24981 OUT (253),A
24983 IN A,(254)
24985 AND %00011110 Strip out the SHIFT key.
24987 CP 30 If none of these keys have been pressed, jump to ReadInputLR_7F.
24989 JR Z,ReadInputLR_7F
24991 AND %00010100 Keep only bits 2 ("X") and 4 ("V").
24993 CP 20 If neither key is pressed jump to Input_Left.
24995 JR Z,Input_Left
24997 JR Input_Right Jump to Input_Right.
Check for "Left" and "Right" button input for port 127.
ReadInputLR_7F 24999 LD A,127 Read from the keyboard;
Port Number Bit
0 1 2 3 4
$7F SPACE FULL-STOP M N B
25001 OUT (253),A
25003 IN A,(254)
25005 AND %00011110 Strip out the SPACE key.
25007 CP 30 If none of these keys have been pressed, jump to Input_None.
25009 JR Z,Input_None
25011 AND %00010100 Keep only bits 2 ("M") and 4 ("B").
25013 CP 20 If neither key is pressed jump to Input_Right.
25015 JR Z,Input_Right
Return "Left" button pressed.
Input_Left 25017 LD A,253 A=11111101.
25019 RET Return.
Return "Right" button pressed.
Input_Right 25020 LD A,254 A=11111110.
25022 RET Return.
Return "no input".
Input_None 25023 LD A,255 A=11111111.
25025 RET Return.
View the equivalent code in;
Prev: 24968 Up: Map Next: 25026