Routines
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6B99: Print Instructions Menu
instructions
Print_InstructionsMenu 6B99 CALL ClearScreen Call ClearScreen.
6B9C LD A,($66F6) Jump to Input_SelectLevel if *ControlMethod is a joystick method.
6B9F OR A
6BA0 JR NZ,Input_SelectLevel
The player has selected to use the keyboard, so remind them what the keys are.
Print "Instructions".
6BA2 LD HL,$6476 Call Configurable_PrintString using Messaging_Instructions; printing 0C characters in YELLOW.
6BA5 LD DE,$40A9
6BA8 LD BC,$0C06
6BAB CALL Configurable_PrintString
Print "Left".
6BAE LD DE,$4807 Call Configurable_PrintString using Messaging_Left; printing 14 characters in INK:MAGENTA, PAPER:BLACK(BRIGHT).
6BB1 LD BC,$1443
6BB4 CALL Configurable_PrintString
Print "Right".
6BB7 LD E,$47 Call Configurable_PrintString using Messaging_Right; printing 0B characters.
6BB9 LD B,$0B
6BBB CALL Configurable_PrintString
Print "Fire".
6BBE LD E,$87 Call Configurable_PrintString using Messaging_Fire; printing 0F characters.
6BC0 LD B,$0F
6BC2 CALL Configurable_PrintString
Print "Barrier".
6BC5 LD E,$C7 Call Configurable_PrintString using Messaging_Barrier; printing 0F characters.
6BC7 LD B,$0F
6BC9 CALL Configurable_PrintString
Print "Select Level".
Input_SelectLevel 6BCC LD HL,$64BF Call Configurable_PrintString using Messaging_Level; printing 12 characters in WHITE.
6BCF LD DE,$5087
6BD2 LD BC,$1207
6BD5 CALL Configurable_PrintString
Read keyboard input to select level 1-5.
Input_SelectLevel_Loop 6BD8 DI Disable interrupts.
6BD9 LD A,$F7 Read from the keyboard;
Port Number Bit
0 1 2 3 4
F7 1 2 3 4 5
6BDB IN A,($FE)
6BDD XOR %11111111 Flip the bits.
6BDF AND %00011111 Keep only bits 0-4 (the key states).
6BE1 JR Z,Input_SelectLevel_Loop Jump to Input_SelectLevel_Loop if no keys were pressed.
6BE3 LD C,$31 Start a count in C starting at 31 (ASCII "1").
6BE5 BIT 0,A Jump to Input_SelectLevel_Store if bit 0 of A was set (key "1" pressed).
6BE7 JR NZ,Input_SelectLevel_Store
6BE9 INC C Increment C by one (ASCII "2").
6BEA BIT 1,A Jump to Input_SelectLevel_Store if bit 1 of A was set (key "2" pressed).
6BEC JR NZ,Input_SelectLevel_Store
6BEE INC C Increment C by one (ASCII "3").
6BEF BIT 2,A Jump to Input_SelectLevel_Store if bit 2 of A was set (key "3" pressed).
6BF1 JR NZ,Input_SelectLevel_Store
6BF3 INC C Increment C by one (ASCII "4").
6BF4 BIT 3,A Jump to Input_SelectLevel_Store if bit 3 of A was set (key "4" pressed).
6BF6 JR NZ,Input_SelectLevel_Store
6BF8 INC C Increment C by one (ASCII "5").
6BF9 BIT 4,A Jump to Input_SelectLevel_Loop if bit 4 of A was set (key "5" pressed).
6BFB JR Z,Input_SelectLevel_Loop
Input_SelectLevel_Store 6BFD LD HL,$6527 Write C to *Messaging_Header_LevelNumber.
6C00 LD (HL),C
6C01 LD A,C Convert the ASCII digit to a numeric value by, subtracting 30 multiply by 02 and subtracting the result from 0A e.g.
ASCII Byte Result
"1" 31 8
"2" 32 6
"3" 33 4
"4" 34 2
"5" 35 0
Write the result to *6898.
6C02 SUB $30
6C04 ADD A,A
6C05 LD C,A
6C06 LD A,$0A
6C08 SUB C
6C09 LD ($6898),A
6C0C RET Return.
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