Routines
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6966: Pause Border Effect
Used by the routine at Game_Initialise.
Displays a rainbow-like cycling colour border while waiting for the player to press "S" to unpause the game.
Pause_BorderEffect 6966 EI Enable interrupts.
6967 LD B,$14 Pause for 14 frames to give the player a moment before the effect begins.
Pause_BorderEffect_ShortLoop 6969 HALT
696A DJNZ Pause_BorderEffect_ShortLoop
Pause_BorderEffect_ColourCycle 696C LD B,$0E Set a frame counter in B of 0E frames.
696E HALT Halt operation (suspend CPU until the next interrupt).
Derive a border colour (00-07) from the current frame loop counter.
Pause_BorderEffect_ColourLoop 696F LD A,B Load A with bits 0-2 of the current frame counter value. This limits the value to be between 00-07 (i.e. the colour palette).
6970 AND %00000111
6972 PUSH BC Stash the frame counter on the stack.
Pause_Border_PauseLoop_01 6973 DJNZ Pause_Border_PauseLoop_01 Decrease the frame counter by one and loop until the counter is zero.
6975 POP BC Restore the frame counter from the stack.
6976 PUSH BC But keep a copy of it back on the stack.
6977 LD B,$00 Set B to 00 which increases the size of the counter.
Pause_Border_PauseLoop_02 6979 DJNZ Pause_Border_PauseLoop_02 Decrease the frame counter by one and loop again until the counter is zero.
697B POP BC Restore the frame counter from the stack.
697C OUT ($FE),A Set border to the colour held by A.
697E DJNZ Pause_BorderEffect_ColourLoop Decrease counter by one and loop back to Pause_BorderEffect_ColourLoop until counter is zero.
6980 LD A,$FD Read from the keyboard;
Port Number Bit
0 1 2 3 4
FD A S D F G
6982 IN A,($FE)
6984 AND %00000010 Keep only the bit which relates to the "S" key (bit 1).
6986 JR NZ,Pause_BorderEffect_ColourCycle Jump back to Pause_BorderEffect_ColourCycle if the "S" key was not pressed.
6988 LD A,$FD Read from the keyboard again;
Port Number Bit
0 1 2 3 4
FD A S D F G
StartKey_Debounce 698A IN A,($FE)
698C AND %00000010 Keep only the bit which relates to the "S" key (bit 1).
698E JR Z,StartKey_Debounce Jump to StartKey_Debounce until the "S" key has been released.
6990 DI Disable interrupts.
6991 RET Return.
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