Routines
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83AA: Game Selection Menu
Used by the routine at GameInitialise.
main-menu
Prints "Select controls".
GameMenu 83AA LD HL,$8B31 HL=Messaging_SelectControls.
83AD LD DE,$504B DE=504B (screen buffer location).
83B0 CALL Print_String Call Print_String.
83B3 LD HL,$506B HL=506B (screen buffer location).
83B6 LD B,$0F Underline the header with 0F character blocks of FF.
83B8 CALL Underline
Prints "1 User defined keys".
83BB LD HL,$8B40 HL=Messaging_UserDefinedKeys.
83BE LD DE,$5089 DE=5089 (screen buffer location).
83C1 CALL Print_String Call Print_String.
Prints "2 Kempston joystick".
83C4 LD HL,$8B53 HL=Messaging_KempstonJoystick.
83C7 LD DE,$50A9 DE=50A9 (screen buffer location).
83CA CALL Print_String Call Print_String.
Prints "3 Interface 2".
83CD LD HL,$8B66 HL=Messaging_Interface2.
83D0 LD DE,$50C9 DE=50C9 (screen buffer location).
83D3 CALL Print_String Call Print_String.
Prints "4 Cursor key type J/S".
83D6 LD HL,$8B73 HL=Messaging_CursorKeys.
83D9 LD DE,$50E9 DE=50E9 (screen buffer location).
83DC CALL Print_String Call Print_String.
Handle retrieving the players input.
GameMenu_InputLoop 83DF LD BC,$F7FE Read from the keyboard;
Port Number Bit
0 1 2 3 4
F7 1 2 3 4 5
83E2 IN A,(C)
83E4 OR %11100000 Set bits 5-7 (to fill in the extra bits).
83E6 CP $FF Jump to GameMenu_HandleInput if any of the keys have been pressed.
83E8 JR NZ,GameMenu_HandleInput
83EA LD B,$05 Call 8055 with a count of 05.
83EC CALL $8055
83EF JR GameMenu_InputLoop Jump to GameMenu_InputLoop.
Process the players input.
GameMenu_HandleInput 83F1 CP $FE Jump to SetUserDefinedKeys if A is equal to FE.
83F3 JR Z,SetUserDefinedKeys
Was Kempston joystick selected?
83F5 LD HL,$8E55 HL=KeyMap_Kempston.
83F8 CP $FD Jump to SetKempstonJoystick if A is equal to FD.
83FA JR Z,SetKempstonJoystick
Was Interface 2 joystick selected?
83FC LD HL,$8E64 HL=KeyMap_Interface2.
83FF CP $FB Jump to SetNoOperation if A is equal to FB.
8401 JR Z,SetNoOperation
Was the Cursor joystick selected?
8403 LD HL,$8E73 HL=KeyMap_CursorKeys.
8406 CP $F7 Jump back to GameMenu_InputLoop if the cursor joystick was not selected.
8408 JR NZ,GameMenu_InputLoop
Self-modifying code. See; HandleControlBits.
SetNoOperation 840A LD A,$00 Write 00 (NOP) to *HandleControlBits.
SetActiveKeyMap 840C LD ($85F4),A Write A to *HandleControlBits.
840F LD DE,$EFE0 Copy 000F bytes from *HL to *ActiveKeyMap.
8412 LD BC,$000F
8415 LDIR
8417 RET Return.
Self-modifying code. See; HandleControlBits.
Invert the bits in the controls routine.
SetKempstonJoystick 8418 LD A,$2F A=2F (CPL) to *HandleControlBits.
841A JR SetActiveKeyMap Jump to SetActiveKeyMap.
Self-modifying code. See; HandleControlBits.
SetUserDefinedKeys 841C LD A,$00 Write 00 (NOP) to *HandleControlBits.
841E LD ($85F4),A
8421 CALL ClearBottomScreenArea Call ClearBottomScreenArea.
Prints "Please select ".
8424 LD HL,$8B88 HL=Messaging_PleaseSelectKeys.
8427 LD DE,$50A7 DE=50A7 (screen buffer location).
842A CALL Print_String Call Print_String.
Cycle through each key/ key messaging to collect the user input:
Using "right key", "down key", "left key", "up key" and "fire key" strings.
842D LD HL,$8B96 HL=Messaging_RedefineKeys_Right.
8430 LD B,$05 Store a counter in B of 05 for how many strings to print.
8432 LD IX,$EFE0 IX=ActiveKeyMap.
SetKeys_Loop 8436 PUSH BC Stash the string counter and active keymap position on the stack.
8437 PUSH IX
8439 LD DE,$50B5 DE=50B5 (screen buffer location).
843C CALL Print_String Call Print_String.
843F PUSH HL Stash the messaging pointer on the stack.
GameMenu_0 8440 CALL PauseCheck Call PauseCheck.
GameMenu_1 8443 LD B,$05 Call 8055 with a count of 05.
8445 CALL $8055
8448 LD BC,$FEFE Read from the keyboard;
Port Number Bit
0 1 2 3 4
FE SHIFT Z X C V
GameMenu_2 844B IN A,(C)
844D OR %11100000 Set bits 5-7 (to fill in the extra bits).
844F CP $FF Jump to GameMenu_3 if any of the keys have been pressed.
8451 JR NZ,GameMenu_3
8453 RLC B Rotate B left (with carry).
8455 JR C,GameMenu_2 Jump to GameMenu_2 if A is lower.
8457 JR GameMenu_1 Jump to GameMenu_1.
GameMenu_3 8459 CPL Invert the bits in A.
845A AND %00011111 Keep only bits 0-4.
845C LD E,A E=A.
GameMenu_4 845D RRA RRA.
845E JR NC,GameMenu_4 Jump to GameMenu_4 if A is higher.
8460 CP $00 Jump to GameMenu_0 if A is not equal to 00.
8462 JR NZ,GameMenu_0
8464 POP HL Restore the messaging pointer and active keymap position from the stack.
8465 POP IX
8467 LD (IX+$00),C Write the keymap data to the current active key.
846A LD (IX+$01),B
846D LD (IX+$02),E
8470 LD BC,$0003 Add 0003 to IX to move to the next key.
8473 ADD IX,BC
8475 POP BC Restore the string counter from the stack.
8476 DJNZ SetKeys_Loop Decrease the string counter by one and loop back to SetKeys_Loop until all keys have been collected.
8478 RET Return.
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