Routines
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6A77: Make the title screen or game over sound effect
Used by the routines at 6000 (on the title screen) and 673A (when a game is over).
6A77 LD HL,$7C69 Pick up the sound on/off indicator.
6A7A LD C,$10 Initialise C for the loop that follows.
6A7C PUSH BC Save the loop counter (unnecessarily).
6A7D LD B,C Set B and D equal to 8*C. This value determines the pitch.
6A7E SLA B
6A80 SLA B
6A82 SLA B
6A84 LD D,B
6A85 LD E,$0A This value determines the duration.
6A87 LD B,D Produce a sound (if the sound on/off indicator is on) with pitch and duration determined by D and E.
6A88 LD A,$1F
6A8A AND (HL)
6A8B OUT ($FE),A
6A8D DJNZ $6A8D
6A8F LD A,$07
6A91 OUT ($FE),A
6A93 LD B,D
6A94 DJNZ $6A94
6A96 DEC E
6A97 JR NZ,$6A87
6A99 POP BC Restore the loop counter to C (unnecessarily).
6A9A DEC C Finished yet?
6A9B JR NZ,$6A7C Jump back if not.
6A9D RET
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